Radio wave reflection device

Abstract

This radio wave reflection device has: a radio wave reflection region in which a plurality of reflective elements for reflecting radio waves are arranged in an array; and a peripheral region that surrounds the radio wave reflection region and in which a radio wave absorption pattern is disposed. Each of the reflective elements includes: a patch electrode disposed on a surface on which the radio waves are incident; a control electrode facing the patch electrode; and a liquid crystal layer disposed between the patch electrode and the control electrode. In the radio wave reflection region, the control electrodes of the plurality of reflective elements are connected by stripline wiring so as to have the same potential. In the peripheral region, the outline of the radio wave absorption pattern has a width greater than that of the stripline wiring, and the radio wave absorption pattern is connected to the patch electrodes by the stripline wiring.

Description

Radio wave reflection device

[0001] One embodiment of the present invention relates to a radio wave reflection device.

[0002] Since liquid crystal molecules have dielectric anisotropy, by adjusting the electric field applied to the liquid crystal layer containing the liquid crystal molecules to control the orientation of the liquid crystal molecules, the dielectric constant of the liquid crystal layer can be controlled. It is known that by utilizing such characteristics, a radio wave reflection device capable of controlling reflection characteristics can be provided (see, for example, Patent Documents 1 and 2).

[0003] Japanese Patent Application Laid-Open No. 11-103201, Japanese Patent Application Laid-Open No. 2019-530387

[0004] In the radio wave reflection device, a plurality of reflection elements capable of controlling the dielectric constant of the liquid crystal layer are provided, and wiring for applying a voltage to the reflection elements is provided around the region where these reflection elements are arranged. There is a problem that radio waves hitting and reflecting in the region where these wirings are provided deteriorate the reflection amplitude of the reflected waves reflected by the reflection elements and cannot control the reflection direction of the radio waves in a desired direction.

[0005] One embodiment of the present invention has an object of providing a radio wave reflection device including a liquid crystal layer and having excellent radio wave reflection characteristics.

[0006] One embodiment of the present invention is a radio wave reflection device. The radio wave reflection device has a radio wave reflection region in which a plurality of reflection elements for reflecting radio waves are arranged, and a peripheral region surrounding the radio wave reflection region and in which a radio wave absorption pattern is arranged. Each of the plurality of reflection elements includes a patch electrode arranged on the surface on the incident side of the radio wave, a control electrode facing the patch electrode, and a liquid crystal layer arranged between the patch electrode and the control electrode. In the radio wave reflection region, the control electrodes of the plurality of reflection elements are connected by strip wiring so as to have the same potential. In the peripheral region, the width of the contour of the radio wave absorption pattern is larger than the width of the strip wiring, and the radio wave absorption pattern is connected by the patch electrode and the strip wiring.

[0007] A schematic unfolded perspective view of a radio wave reflector according to one embodiment of the present invention. A schematic end view of a radio wave reflector according to one embodiment of the present invention. A schematic top view of a radio wave reflector according to one embodiment of the present invention. A schematic bottom view of a radio wave reflector according to one embodiment of the present invention. A schematic bottom view of a radio wave reflector according to one embodiment of the present invention. A schematic bottom view of a radio wave reflector according to one embodiment of the present invention. A schematic bottom view of a radio wave reflector according to one embodiment of the present invention. A schematic bottom view of a radio wave reflector according to one embodiment of the present invention. A schematic bottom view of a radio wave reflector according to one embodiment of the present invention. A schematic bottom view of a radio wave reflector according to one embodiment of the present invention. A schematic bottom view of a radio wave reflector according to one embodiment of the present invention. A plot showing the frequency dependence of the radio wave absorption intensity of the model radio wave absorption pattern of Example 1. A plot showing the frequency dependence of the radio wave absorption intensity of the model radio wave absorption pattern of Example 2.

[0008] The embodiments of the present invention will be described below with reference to the drawings and other materials. However, the present invention can be implemented in various forms without departing from its spirit, and is not to be interpreted as being limited to the embodiments described below.

[0009] While drawings may schematically represent the width, thickness, shape, etc., of each part to clarify the explanation, they are merely examples and do not limit the interpretation of the present invention. In this specification and in each drawing, elements having the same function as those described in previously shown drawings are denoted by the same reference numerals, and redundant explanations may be omitted.

[0010] In this specification and claims, when describing a manner in which one structure is placed on top of another structure, unless otherwise specified, the term "on top of" includes both cases: when one structure is placed directly on top of another structure so as to be in contact with it, and when another structure is placed above another structure via yet another structure.

[0011] In embodiments of the present invention, when multiple films are formed simultaneously in the same process, these films have the same layer structure, the same material, and the same composition. Therefore, these multiple films are defined as existing within the same layer.

[0012] 1. Configuration of the Radio Wave Reflector The configuration of the radio wave reflector 100, which is one embodiment of the present invention, will be described below. The radio wave reflector 100 is a so-called liquid crystal radio wave reflector, and is a device that utilizes the change in dielectric constant caused by the change in orientation of the liquid crystal layer due to an electric field to reflect irradiated radio waves in any direction. There are no restrictions on the frequency of the wavelength that can be reflected, for example, it is in the range of 400 MHz to 50 GHz. Typically, the radio wave reflector 100 can be used to reflect radio waves in the 400 MHz to 6.0 GHz band, the 2.5 GHz to 4.7 GHz band, and the 24 GHz to 50 GHz band.

[0013] Figure 1 shows a schematic unfolded perspective view of the radio wave reflector 100. The radio wave reflector 100 has a substrate (hereinafter referred to as the array substrate) 102 and a counter substrate 104, and multiple radio wave reflecting elements are provided between the array substrate 102 and the counter substrate 104, arranged in a matrix shape with multiple columns and rows. The area where the radio wave reflecting elements are arranged (a single rectangular area that simultaneously encloses all the radio wave reflecting elements) is called the radio wave reflection area RA. In the radio wave reflection area RA, incident radio waves can be reflected in any direction using the radio wave reflecting elements. The area surrounding the radio wave reflection area RA is called the frame area or peripheral area FA.

[0014] A drive circuit (scan line drive circuit 106, signal line drive circuit 108) for driving the radio wave reflecting elements can be provided in the peripheral region FA of the array substrate 102. Further, multiple wirings (not shown in Figure 1) are provided on the array substrate 102. These wirings electrically connect the drive circuits and the radio wave reflecting elements, and at least a portion of them extends through the peripheral region FA to reach the edge of the array substrate 102. The wirings are exposed at the edge of the array substrate 102, forming multiple terminals 110. Flexible printed circuit (FPC) boards (not shown) are connected to the terminals 110. Various drive signals for driving the radio wave reflecting device 100 are supplied from an external circuit via the flexible printed circuit and terminals 110. Based on these signals, the drive circuit generates control signals for controlling the radio wave reflecting elements and supplies them to the elements. Alternatively, the scan line drive circuit 106 and / or the signal line drive circuit 108 may be omitted, and control signals may be supplied directly from the external circuit to the radio wave reflecting elements via the wiring.

[0015] A radio wave absorption pattern 200 is provided in the peripheral region FA of the opposing substrate 104 to absorb radio waves. The radio wave absorption pattern 200 functions as wiring used to supply a constant potential (common potential) to the patch electrode 150. As will be described in detail later, the radio wave absorption pattern 200 is provided to absorb a portion of the radio waves incident on the radio wave reflector 100 and suppress reflection in the peripheral region FA. These configurations will be described in detail below.

[0016] (1) Array substrate and opposing substrate Figure 2 shows a schematic end view of the radio wave reflector 100. This figure shows a part of the multiple radio wave reflecting elements 140 provided in the radio wave reflection region RA, and a schematic end view of the surrounding region FA. The array substrate 102 and the opposing substrate 104 face each other, providing physical strength to the radio wave reflector 100 and providing a surface for arranging the radio wave reflecting elements 140. The array substrate 102 and the opposing substrate 104 may include inorganic insulators such as glass and quartz, semiconductors such as silicon, polymers such as polyimide, polycarbonate and polyester, and metals such as aluminum, copper and stainless steel. If conductive materials such as metals are included, it is preferable to provide an undercoat 112 and an overcoat 132 on the surface on which the radio wave reflecting elements 140 are provided, i.e., the surface of the array substrate 102 on the side of the opposing substrate 104 and the surface of the opposing substrate 104 on the side of the array substrate 102. The array substrate 102 and the opposing substrate 104 may or may not transmit visible light. Furthermore, the array substrate 102 and / or the opposing substrate 104 may be flexible. The array substrate 102 and the opposing substrate 104 are fixed to each other by a sealing material 152, either directly or via a first alignment film 144 and a second alignment film 148, which will be described later.

[0017] (2) Radio wave reflecting element As shown in Figure 2, each of the plurality of radio wave reflecting elements 140 includes a control electrode 142, a first alignment film 144 on the control electrode 142, a liquid crystal layer 146 on the first alignment film 144, a second alignment film 148 on the liquid crystal layer 146, and a patch electrode 150 on the second alignment film 148. Radio waves are incident from the patch electrode 150 side.

[0018] Each radio wave reflecting element 140 is connected to an element circuit that includes at least one transistor 120. Each element circuit may include multiple transistors and may further include one or more capacitive elements. As can be seen from Figure 2, the element circuits including the transistors 120 and the radio wave reflecting elements 140 are provided on the array substrate 102 via an undercoat 112, either directly or in any configuration. The transistors 120 included in the element circuit are not restricted in their structure and may be bottom-gate or top-gate transistors. Alternatively, the transistor 120 may be a transistor having gate electrodes on the top and bottom of a semiconductor film. The transistor 120 illustrated in Figure 2 is a bottom-gate transistor and consists of a gate electrode 122, a gate insulating film 124 on the gate electrode 122, a semiconductor film 126 on the gate insulating film 124, and a pair of terminals 128 and 130 on the semiconductor film 126. A planarization film 116 is provided on the transistor 120, and the radio wave reflecting elements 140 are formed thereon. As an optional configuration, interlayer insulating films 114 and 118 may be provided between the transistor 120 and the planarization film 116, or on the planarization film 116, respectively.

[0019] The control electrode 142 of the radio wave reflecting element 140 is electrically connected to the transistor 120 via an opening provided in the interlayer insulating film 118 or the planarization film 116. Various signals supplied from an external circuit are supplied to the radio wave reflecting element 140 directly or via a drive circuit through the wiring 134 that constitutes the terminal 110. As shown in Figure 2, at least a portion of the wiring 134 extends over the peripheral region FA. The wiring 134 may be in the same layer as the gate electrode 122, or in the same layer as the terminals 128 and 130. Alternatively, a portion of the wiring 134 may be in the same layer as the gate electrode 122, and another portion may be in the same layer as the terminals 128 and 130.

[0020] The gate electrode 122, gate insulating film 124, semiconductor film 126, terminals 128 and 130 that constitute the transistor 120, as well as the interlayer insulating films 114 and 118, planarization film 116, and wiring 134 that cover the transistor 120, can be formed using known materials and applying known methods as appropriate, so a detailed explanation will be omitted. Briefly, the gate electrode 122, terminals 128 and 130, and wiring 134 are formed by forming a film containing metals such as tantalum, molybdenum, titanium, and aluminum using sputtering or chemical vapor deposition (CVD), and then appropriately patterning this film using a photolithography process. The semiconductor film 126 is formed as a film containing group 14 elements, such as silicon, or as a film containing oxides of group 13 elements such as indium and gallium. The semiconductor film 126 can also be formed by applying sputtering or CVD. The gate insulating film 124, interlayer insulating films 114 and 118, undercoat 112, and overcoat 132 contain inorganic compounds such as silicon-containing inorganic compounds like silicon oxide and silicon nitride, and are formed by sputtering or CVD. The planarization film 116 contains polymers such as acrylic resin, epoxy resin, polyimide, polyamide, and silicon resin, and can be formed using wet film formation methods such as spin coating, inkjet printing, or other appropriate methods. By providing the planarization film 116, the radio wave reflecting element 140 can be formed on a flat surface.

[0021] The control electrode 142 of the radio wave reflecting element 140 may include, for example, metals such as copper, aluminum, tungsten, molybdenum, and titanium, or alloys containing at least one of these metals. Alternatively, the control electrode 142 may include a light-transmitting conductive oxide such as indium-zinc oxide (IZO) or indium-tin oxide (ITO). The control electrode 142 may have a single-layer structure or a laminated structure in which layers of different compositions are stacked. For example, a laminated structure of a layer containing a conductive oxide and a layer containing the above-mentioned metal or alloy may be adopted. Alternatively, in order to impart light transmittance to the control electrode 142 containing the metal or alloy, the control electrode 142 may have a mesh shape.

[0022] The first alignment film 144, provided on a plurality of control electrodes 142, is provided to control the orientation of liquid crystal molecules constituting the liquid crystal layer 146 provided thereon. The first alignment film 144 can be provided continuously across a plurality of radio wave reflecting elements 140. In other words, the first alignment film 144 can be provided so as to be shared by all radio wave reflecting elements 140 without being interrupted between adjacent radio wave reflecting elements 140.

[0023] The first alignment film 144 contains a polymer such as polyimide or polyester. The first alignment film 144 is formed using a wet film formation method such as inkjet, spin coating, printing, or dip coating, and its surface is rubbed. Alternatively, the first alignment film 144 may be formed by photoalignment treatment.

[0024] The liquid crystal layer 146 is sealed between the array substrate 102 and the opposing substrate 104 by a sealing material 152. The liquid crystal layer 146 is placed in the radio wave reflection region RA, which is the region surrounded by the sealing material 152. The liquid crystal layer 146 is placed between the patch electrode 150 and the control electrode 142. The structure of the liquid crystal molecules contained in the liquid crystal layer 146 is not limited. Therefore, the liquid crystal molecules may be nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, or chiral smectic liquid crystals. The thickness of the liquid crystal layer 146 is, for example, 20 μm or more and 50 μm or less, or 30 μm or more and 50 μm or less. Although not shown, spacers may be provided within the liquid crystal layer 146 to maintain this thickness throughout the entire radio wave reflection device 100. Note that if the above-described thickness of the liquid crystal layer 146 is adopted in a liquid crystal display device, it will not be possible to obtain the high responsiveness necessary to display moving images, and it will be extremely difficult to exhibit the function of a liquid crystal display device.

[0025] A second alignment film 148 is also provided to control the orientation of liquid crystal molecules and has the same configuration as the first alignment film 144. The second alignment film 148 can also be formed to be continuous across adjacent radio wave reflecting elements 140 and shared by multiple radio wave reflecting elements 140. The first alignment film 144 and the second alignment film 148 are arranged such that the direction in which the first alignment film 144 orients the liquid crystal molecules is parallel to that of the second alignment film 148. The liquid crystal molecules are oriented in a certain direction by the first alignment film 144 and the second alignment film 148.

[0026] The patch electrode 150 is placed on the opposing substrate 104, which is the surface of the radio wave reflection device 100 that is the incident side of the radio waves. A patch electrode 150 is provided for each radio wave reflection element 140. Therefore, the patch electrode 150 is also arranged in a matrix shape having multiple rows and columns, and in each radio wave reflection element 140, the patch electrode 150 overlaps with the control electrode 142. The patch electrode 150 is placed opposite the control electrode 142. As described above, radio waves are incident from the patch electrode 150 side. For this reason, it is preferable that the patch electrode 150 has a highly symmetrical shape such as a regular polygon or a circle in order to efficiently reflect both orthogonal components of the radio waves (vertical polarization and horizontal polarization). It is preferable that the patch electrode 150 is rectangular, as shown in Figure 1 or Figure 3 described later. The size of the patch electrode 150 can be appropriately adjusted according to the wavelength of the radio waves to be reflected, and for example, the length in the row direction and the length in the column direction can be appropriately selected from the range of 1 mm to 40 mm. Although not shown in the diagram, multiple patch electrodes 150 are electrically connected to each other in the row direction and / or in the row direction by connecting wiring. A constant potential (common potential) is supplied to the patch electrodes 150 from an external circuit or a signal line drive circuit 108 via the wiring. By supplying a constant potential, multiple patch electrodes 150 in the radio wave reflection region RA are at the same potential. The connecting wiring to which the multiple patch electrodes 150 are connected corresponds to the strip wiring 154 in the radio wave reflection region RA, which will be described later.

[0027] Similar to the control electrode 142, the patch electrode 150 may also contain metals such as copper, aluminum, tungsten, molybdenum, or titanium, alloys containing at least one of these metals, or conductive oxides such as ITO or IZO. The patch electrode 150 may have a single-layer structure or a laminated structure in which layers of different compositions are stacked. The patch electrode 150 may also be formed by applying methods such as sputtering or CVD. The radio wave reflecting element 140 may or may not transmit visible light. For example, visible light may be blocked by using a metal or alloy with a thickness that does not transmit visible light for the control electrode 142 and the patch electrode 150.

[0028] In the radio wave reflector 100, as described above, the first alignment layer 144 and the second alignment layer 148 are parallel in the direction in which they orient the liquid crystal molecules. Therefore, when no potential difference is applied between the control electrode 142 and the patch electrode 150, no longitudinal electric field is generated within the liquid crystal layer 146, and the liquid crystal molecules are spray-oriented. The orientation of the liquid crystal layer 146 is the same between the radio wave reflectors 140, and therefore the dielectric constant is also constant within the liquid crystal layer 146, so the spread (phase) of the reflected wave generated when radio waves incident from the patch electrode 150 side are reflected off the surface of the patch electrode 150 does not change. As a result, the incident radio waves are specularly reflected by the radio wave reflector 100, and the reflected wave is given at the same exit angle as the incident angle.

[0029] In contrast, by applying a voltage to the control electrode 142 that creates a potential difference between the control electrode 142 and the patch electrode 150, the orientation state of the liquid crystal layer can be changed. When the voltage applied to the control electrode 142 is controlled using an element circuit to create a potential difference between the control electrode 142 and the patch electrode 150, the generated longitudinal electric field causes the liquid crystal molecules to stand up and bend. At this time, if longitudinal electric fields of different intensities are generated between the radio wave reflecting elements 140, the dielectric constant of the liquid crystal layer 146 changes between the radio wave reflecting elements 140 according to the intensity of the longitudinal electric field. As a result, the phase of the reflected wave changes, and consequently, the reflection direction of the radio waves incident on the radio wave reflection region RA can be changed. The reflection direction can be arbitrarily controlled by changing the intensity of the longitudinal electric field formed on the radio wave reflecting elements 140.

[0030] (3) Radio wave absorption pattern As shown in Figures 1 and 2, the radio wave absorption pattern 200 can be placed in the peripheral region FA and placed on top of the sealing material 152. The radio wave absorption pattern 200 may be placed on top of a part of the liquid crystal layer 146 as well as the sealing material 152. The radio wave absorption pattern 200 can be formed in the same layer as the patch electrode 150. The radio wave absorption pattern 200 can be formed on the opposing substrate 104, for example, as shown in Figure 2, or it may be formed by laminating it on the overcoat 132 on the opposing substrate 104.

[0031] Figure 3 shows a schematic top view of the opposing substrate 104. Figure 3 is a schematic view of the opposing substrate 104 as seen from the side into which the radio waves are incident. The patch electrodes 150, the radio wave absorption pattern 200, and the strip wiring 154 are shown by solid lines. As can be seen from Figures 1 and 2, the radio wave absorption pattern 200 is provided so as to overlap with the peripheral region FA of the array substrate and overlap with at least a portion of the scan line drive circuit 106 and the wiring connected to the scan line drive circuit 106 on the peripheral region FA. In the example shown in Figures 1 and 3, the radio wave absorption pattern 200 is not provided in the peripheral region FA on the terminal 110 side. The radio wave absorption pattern 200 is arranged in two regions that sandwich the multiple patch electrodes 150 in parallel, but the radio wave absorption pattern 200 may also be provided in the peripheral region FA on the terminal 110 side and the side opposite to the terminal 110, so as to surround all four sides of the radio wave reflection region RA.

[0032] The radio wave absorption pattern 200 is connected to the patch electrode 150 by strip wiring 154. Therefore, as described above, a constant potential is applied to the patch electrode 150 via the strip wiring 154 and the radio wave absorption pattern 200.

[0033] The radio wave absorbing pattern 200 may contain conductive oxides such as ITO or IZO, or metals such as copper, aluminum, tungsten, molybdenum, or titanium, or alloys containing at least one of these metals. Preferably, the radio wave absorbing pattern 200 may contain highly conductive metals such as titanium, molybdenum, or tungsten so that it exhibits high radio wave absorption characteristics. Since the radio wave absorbing pattern 200 is connected to the strip wiring 154, it is preferable that the strip wiring 154 also contains the same material as the radio wave absorbing pattern 200.

[0034] Figure 4 shows a schematic bottom view of the radio wave absorption pattern 200, strip wiring 154, and patch electrode 150. Figure 4 is a schematic view of the opposing substrate 104 as seen from the radio wave absorption pattern 200 side. Specifically, it is an enlarged view of a portion 156 shown in Figure 4.

[0035] The radio wave absorption patterns 200 may be arranged at the same spacing 150D as the spacing 150D in the direction in which the patch electrodes 150 are arranged. As shown in Figure 4, the radio wave absorption patterns 200 can be arranged at the same spacing 150D as the spacing 150D in the x-axis direction of the patch electrodes 150.

[0036] Multiple radio wave absorbing patterns 200 are arranged in the surrounding area FA, and these multiple radio wave absorbing patterns 200 can be connected to each other by strip wiring 154. The width 200W of the contour 200C of the radio wave absorbing pattern 200 is greater than the width 154W of the strip wiring. For example, as shown in Figure 4, the width 200W of the contour of the radio wave absorbing pattern 200 in the x-axis direction is greater than the width 154W of the strip wiring 154 in the x-axis direction. It is preferable that the dimensions of the radio wave absorbing pattern 200 differ from the dimensions of the patch electrode 150.

[0037] The radio wave absorption pattern 200 can be designed to be larger than the patch electrode 150. When the dielectric constant of the sealing material 152 placed on top of the radio wave absorption pattern 200 is smaller than the dielectric constant of the liquid crystal of the liquid crystal layer 146 placed on top of the patch electrode 150, and the contours of the radio wave absorption pattern 200 and the patch electrode 150 are square, it is preferable that the width 200W of the radio wave absorption pattern or the length of one side of the radio wave absorption pattern 200 is longer than the width 150W of the patch electrode or the length of one side of the patch electrode 150, as shown in Figure 4.

[0038] The radio wave absorption pattern 200 can be designed to be smaller than the patch electrode 150. If the dielectric constant of the sealing material 152 placed on top of the radio wave absorption pattern 200 is greater than the dielectric constant of the liquid crystal of the liquid crystal layer 146 placed on top of the patch electrode 150, and the contours of the radio wave absorption pattern 200 and the patch electrode 150 are square, it is preferable that the width 200W of the radio wave absorption pattern or the length of one side of the radio wave absorption pattern 200 be shorter than the width 150W of the patch electrode or the length of one side of the patch electrode 150.

[0039] Since the radio wave absorption pattern 200 or a part of it is embedded in the sealing material 152, and the patch electrode 150 is embedded in the liquid crystal layer, the apparent wavelength perceived by radio waves passing through the sealing material 152 and the liquid crystal, which have different dielectric constants, changes. By matching the dimensions of the radio wave absorption pattern 200 and the patch electrode 150 to the dielectric constants of the liquid crystal in the sealing material 152 and the liquid crystal layer, the radio wave absorption pattern 200 can absorb radio waves of a specific frequency different from the radio waves reflected by the radio wave reflecting element 140.

[0040] Figures 5 to 7 show schematic bottom views of the radio wave absorption pattern 200. Figures 5 to 7 are schematic diagrams of the opposing substrate 104 as seen from the radio wave absorption pattern 200 side.

[0041] The radio wave absorption pattern 200 can have shapes such as a highly symmetric rectangle, cross shape, and circular shape, in addition to, for example, a square, as shown in FIGS. 5 to 7. As described above, radio waves are incident from the side of the patch electrode 150. Therefore, it is preferable that the radio wave absorption pattern 200 has a highly symmetric shape so as to efficiently reflect both components (vertical polarization wave, horizontal polarization wave) orthogonal to the radio waves. The connection position between the radio wave absorption pattern 200 and the strip wiring 154 is preferably arranged such that the line connecting them becomes the symmetry axis of the radio wave absorption pattern 200.

[0042] Next, an example in which the contour 200C of the radio wave absorption pattern 200 has a shape such as a rectangle, cross shape, and circular shape in a plan view will be described in detail.

[0043] FIGS. 8, 9, and 10 show schematic bottom views of the radio wave absorption pattern 200. FIGS. 8 and 9 are schematic views of the opposing substrate 104 viewed from the side of the radio wave absorption pattern 200. FIG. 10 is a schematic view in which a bent portion 202 (bent part 202) of the radio wave absorption pattern 200 shown in FIGS. 8 and 9 is enlarged.

[0044] The radio wave absorption pattern 200 can be formed of a linear conductor 204. The radio wave absorption pattern 200 may have a shape in which the linear conductor 204 is bent in a meander shape. The radio wave absorption pattern 200 can have a shape in which the linear conductor 204 is meandered or bent a plurality of times such that the direction in which the patch electrodes 150 are arranged becomes the long side. As shown in FIG. 8, the radio wave absorption pattern 200 can have a shape in which the linear conductor 204 is meandered a plurality of times such that the x-axis direction becomes the long side. By meandering the linear conductor 204 of the radio wave absorption pattern 200 such that the x-axis direction becomes the long side 206 (long side portion 206), absorption can be obtained for a polarization wave (for example, a horizontal polarization wave) vibrating in the x-axis direction.

[0045] As shown in Figure 9, the radio wave absorption pattern 200 can have a shape that meanders or bends multiple times so that the direction in which the strip wiring 154 extends is the longer side. By making the linear conductor 204 of the radio wave absorption pattern 200 meander so that the y-axis direction is the longer side, absorption can be obtained for polarizations that vibrate in the y-axis direction (for example, vertical polarization). Figures 8 and 9 show examples in which the linear conductor 204 meanders so that either the x-axis direction or the y-axis direction is the longer side, but the radio wave absorbing pattern 200 having a linear conductor 204 meandered so that the x-axis direction is the longer side and the radio wave absorbing pattern 200 having a linear conductor 204 meandered so that the y-axis direction is the longer side may be provided in the radio wave reflector 100.

[0046] As described above, when the radio wave absorption pattern 200 has a linear conductor 204, the width 204W of the linear conductor should be greater than the width 154W of the strip wiring. For example, if the width 154W of the strip wiring is 10 μm, the width 204W of the linear conductor is preferably 50 μm to 100 μm. When the linear conductor 204 is meandered such that the x-axis direction is the long side 206, the spacing 204SP between the long sides of the linear conductor 204 is preferably smaller than the width 204W of the linear conductor. If the width 204W of the linear conductor is 50 μm to 100 μm, the spacing 204SP between the long sides of the linear conductor 204 is preferably 3 μm to 10 μm. By appropriately adjusting the width 204W of the linear conductor, the long side 206, and the spacing 204SP between the long sides of the linear conductor 204, absorption for a desired wavelength can be obtained. The wavelength absorbed depends particularly heavily on the longer side 206; therefore, absorption at a desired wavelength can be obtained by adjusting the width of the longer side 206 and the spacing between the longer sides 206. Note that the width 204W of the linear conductor and the spacing 204SP between the longer sides of the linear conductor 204 described above are just examples; absorption at a desired wavelength can be obtained by appropriately adjusting the width 204W of the conductor and the spacing 204SP between the longer sides of the conductor 204 relative to the width 154W of the strip wiring.

[0047] The linear conductor 204 may meander in accordance with the contour 200C of the radio wave absorption pattern 200. It is preferable that the linear conductor 204 meanders such that the outer edges of the bent portions 202 and the outermost long side portions 206 of the meandering linear conductor 204 follow the contour 200C of the radio wave absorption pattern 200. For example, as shown in FIGS. 8 and 9, when the contour 200C of the radio wave absorption pattern 200 is square, the linear conductor 204 is meandered and arranged such that the bent portions 202 and the long side portions 206-1 of the meandering linear conductor 204 with the x-axis direction being the long side follow the contour 200C. In FIGS. 8 and 9, an example is shown where the contour 200C is square and the linear conductor 204 meanders along the square of the contour 200C, but the linear conductor 204 may be meandered along the contour 200C having a shape such as a rectangle, a cross, or a circle in a plan view. As shown in FIG. 11, when the contour 200C of the radio wave absorption pattern 200 is cross-shaped, the linear conductor 204 is meandered and arranged such that the bent portions 202 and the long side portions 206-3 and 206-4 of the meandering linear conductor 204 with the x-axis direction being the long side follow the contour 200C.

[0048] By adopting the above-described shape, wiring width, and their intervals, as shown in the simulation results described in the embodiments, the wavelength of the radio waves absorbed by the radio wave absorption pattern 200 can be selected. As a result, radio wave reflection in the peripheral region FA can be suppressed, and radio waves can be selectively reflected in the radio wave reflection region RA. As will be described later, such characteristics contribute to precise control of the reflection direction.

[0049] As described above, wiring 134 for supplying various signals is provided in the peripheral region FA of the radio wave reflection device 100. Also, a drive circuit may be arranged in the peripheral region FA. Structures such as the wiring 134 and the drive circuit also reflect radio waves, so the radio waves reflected by the radio wave reflection device 100 contain not only the desired reflected waves obtained in the radio wave reflection region RA but also the radio waves reflected in the peripheral region FA. This causes a reduction in the amplitude of the reflected wave, and as a result, the reflection characteristics deteriorate.

[0050] However, by arranging the radio wave absorption pattern 200 described above, radio waves incident on the surrounding region FA can be effectively absorbed. As a result, radio waves incident on the radio wave reflector 100 can be selectively reflected in the radio wave reflection region RA, and excellent reflection characteristics can be obtained with suppressed amplitude reduction of the reflected wave. Therefore, a radio wave reflector 100 with excellent reflection characteristics can be provided.

[0051] 2. Example 1 In this example, we describe the results of a simulation analysis of the effect of the difference in width W of the radio wave absorption pattern 200 and the length of the radio wave reflection absorption pattern on the radio wave absorption characteristics of the radio wave absorption pattern 200.

[0052] As shown in Figure 8, eight model radio wave absorption patterns 1 to 8 were constructed, each having a rectangular outline and a meander-shaped bend in a linear conductor. The length of the long side 206 formed by the conductor 204 was set to 1.6 mm. Furthermore, Comparative Example 1 was constructed, which does not have a rectangular electrode, i.e., a meander-shaped bend, as shown in Figure 4. Table 1 shows the wiring width W and wiring spacing SP for model radio wave absorption patterns 1 to 8 and Comparative Example 1. Since Comparative Example 1 does not have a meander shape, it can be said that the wiring width W is equal to the long side 206 and the wiring spacing SP is 0. The electrical conductivity of the radio wave absorption pattern 200 was set to 3.5 × 10^7 S / m, and the dielectric constant of the encapsulating material 152 was set to 2.5, which is the relative dielectric constant of acrylic resin. The simulation was performed for polarization oscillating in the x-axis direction (horizontal polarization) when the linear conductor 204 of model radio wave absorption patterns 1 to 8, as shown in Figure 8, was bent in a meander shape with the x-axis direction as the long side.

[0053]

[0054] Figure 12 shows the simulation results. The vertical axis of the graph in Figure 12 represents the attenuation of the reflected wave amplitude on a common logarithmic scale, with smaller values ​​indicating stronger absorption of radio waves. As can be seen from Figure 12, Comparative Example 1, which has no radio wave absorption pattern, showed almost no radio wave absorption over the frequency band from 40 GHz to 55 GHz. In contrast, Model radio wave absorption patterns 1, 2, 4, 7, and 8, which have radio wave absorption patterns, show strong absorption of radio waves in specific frequency bands. Model radio wave absorption patterns 3, 5, and 6 did not show strong absorption of radio waves.

[0055] When the width W of the strip wiring 154 is 10 μm, it can be seen that the radio wave absorption of the radio wave absorption pattern 200 is significantly more pronounced when the wiring width W of the radio wave absorption pattern 200 is greater than 10 μm. When the width W of the strip wiring 154 is 10 μm, and the wiring width W of the radio wave absorption pattern 200 is between 50 μm and 100 μm, radio waves are absorbed down to 10 dB or less.

[0056] From the above results, it was found that when the strip wiring width 154W is 10 μm, and the width 204W of the linear conductors of the radio wave absorption pattern is between 50 μm and 100 μm, radio waves with wavelengths around 45 GHz can be absorbed. Furthermore, since the absorption peak wavelength differs depending on the width 204W of the linear conductors of the radio wave absorption pattern 200 and their spacing 204SP, it is clearly demonstrated that the radio wave absorption intensity and the frequency of the radio waves absorbed can be controlled by adjusting the width 204W of the linear conductors of the radio wave absorption pattern 200 and their spacing 204SP.

[0057] 3. Example 2 In this example, we describe the results of a simulation analysis of the radio wave absorption characteristics of a model radio wave absorption pattern, as shown in Figure 11, where the contour 200C is cross-shaped, for horizontal polarization oscillating in the x-axis direction and vertical polarization oscillating in the y-axis direction. The model radio wave absorption pattern has linear conductors 204 that are bent into a meander shape with the x-axis direction as the longer side. The width 204W of the linear conductors is 10 μm, and the spacing 204SP between the linear conductors 204 is 11 μm. At this time, the length 206 was 1.6 mm, the length 206-3 was 0.245 mm, and the length 206-4 was 0.55 mm. Other parameters were the same as in Example 1.

[0058] The simulation results are shown in Figure 13. The vertical axis of the graph in Figure 13 shows the attenuation of the reflected wave amplitude on a common logarithmic scale. From Figure 13, it can be seen that horizontal polarization oscillating in the x-axis direction around 41 GHz can be absorbed. In contrast, it can be seen that there is no significant absorption for vertical polarization oscillating in the y-axis direction. Since the linear conductor 204 of the model radio wave absorption pattern has its long side 206 in the x-axis direction, it can be seen that it can effectively absorb polarization oscillating in the direction of the long side. From these results, it can be seen that by arranging the long side of the linear conductor 204, which has a meander-shaped bend, in a desired direction, polarization oscillating in that direction can be controlled.

[0059] The embodiments described above as embodiments of the present invention can be combined and implemented as appropriate, insofar as they do not contradict each other. Furthermore, any additions, deletions, or design modifications of components, or additions, omissions, or changes to processes based on the radio wave reflecting elements or radio wave reflecting devices of each embodiment, made by those skilled in the art, are also included within the scope of the present invention, as long as they retain the essence of the present invention.

[0060] Any effects or benefits other than those brought about by the embodiments described above, if they are clear from the description herein or easily predictable to a person skilled in the art, are naturally considered to be brought about by the present invention.

[0061] 100: Radio wave reflector, 102: Substrate, 102: Array substrate, 104: Opposing substrate, 106: Scan line driving circuit, 108: Signal line driving circuit, 110: Terminal, 112: Undercoat, 114: Interlayer insulating film, 116: Planarization film, 118: Interlayer insulating film, 120: Transistor, 122: Gate electrode, 124: Gate insulating film, 126: Semiconductor film, 128: Terminal, 130: Terminal, 132: Overcoat, 134: Wiring, 140: Radio wave reflector, 142: Control electrode, 144: First alignment layer, 146: Liquid crystal layer, 148: Second alignment layer, 150: Patch electrode, 150D: Spacing, 150W: Width, 152: Encapsulation material, 154: Strip wiring, 154W: Width, 156: Part, 200: Radio wave absorption pattern, 200C: Contour, 200W: Width, 202: Bent portion, 204: Conductor, 204SP: Spacing, 204W: Width, 206: Long side portion, 206: Long side, 206-1: Long side portion, 206-3: Long side portion, 206-4: Long side portion

Claims

1. A radio wave reflecting device comprising: a radio wave reflection region in which a plurality of radio wave reflecting elements that reflect radio waves are arranged; and a peripheral region surrounding the radio wave reflection region in which a radio wave absorption pattern is arranged, wherein each of the plurality of radio wave reflecting elements includes: a patch electrode disposed on the surface facing the radio wave incident side; a control electrode facing the patch electrode; and a liquid crystal layer disposed between the patch electrode and the control electrode, wherein in the radio wave reflection region, the patch electrodes of the plurality of radio wave reflecting elements are connected by strip wiring so that they are at the same potential; and in the peripheral region, the width of the outline of the radio wave absorption pattern is greater than the width of the strip wiring, and the radio wave absorption pattern is connected to the patch electrode by the strip wiring.

2. The radio wave reflecting device according to claim 1, comprising a sealing material surrounding the radio wave reflecting region, wherein the liquid crystal layer is arranged in the region surrounded by the sealing material, and the radio wave absorbing pattern is arranged superimposed on the sealing material.

3. The radio wave reflector according to claim 2, wherein the dielectric constant of the sealing material is greater than the dielectric constant of the liquid crystal of the liquid crystal layer.

4. The radio wave absorbing pattern has a shape in which a linear conductor is bent in a meander shape, as described in claim 1.

5. The radio wave reflector according to claim 1, wherein the shape of the patch electrode in plan view is rectangular, and the shape of the contour of the pre-radio wave absorption pattern in plan view is rectangular.

6. The radio wave reflector according to claim 1, wherein the shape of the patch electrode in plan view is rectangular, and the shape of the contour of the radio wave absorption pattern in plan view is cross-shaped.

7. The radio wave absorbing pattern is arranged at the same spacing as the arrangement of the patch electrodes in the first direction, as described in claim 1.

8. The radio wave reflector according to claim 1, wherein a voltage is applied to the control electrode to change the orientation state of the liquid crystal layer.

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