Radio wave reflection element, radio wave reflection device provided with radio wave reflection element, and antenna

Abstract

This radio wave reflection element includes a patch electrode, an insulating film, an auxiliary electrode, a liquid crystal layer, and a counter electrode. The insulating film is positioned above the patch electrode. The auxiliary electrode has at least one slit or notch that overlaps the patch electrode and is positioned above the insulating film. The liquid crystal layer is positioned above the auxiliary electrode, and the counter electrode is positioned above the liquid crystal layer. The patch electrode and the auxiliary electrode are configured so that a variable potential is individually applied.

Description

Radio wave reflecting element, radio wave reflecting device including radio wave reflecting element, and antenna

[0001] One embodiment of the present invention relates to a radio wave reflecting element using liquid crystal, a radio wave reflecting device including the radio wave reflecting element, and a driving method thereof. Alternatively, one embodiment of the present invention relates to a phase shifter using liquid crystal, an antenna including the phase shifter, a phased array antenna including the antenna, and a driving method thereof.

[0002] Since liquid crystal molecules have dielectric anisotropy, the dielectric constant of the liquid crystal layer can be controlled 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. By utilizing this property, it is possible to realize a radio wave reflector that can control the reflection angle of incident radio waves and a phased array antenna that can transmit directional radio waves in any direction (see, for example, Patent Documents 1 to 3).

[0003] Japanese Patent Laid-Open No. 11-103201 Japanese Patent Laid-Open No. 2019-530387 Japanese Patent Laid-Open No. 2022-25914

[0004] An object of one embodiment of the present invention is to provide a radio wave reflection device that includes a liquid crystal layer and is capable of switching radio wave reflection characteristics at high speed, and a driving method thereof. Alternatively, an object of one embodiment of the present invention is to provide a phased array antenna that includes a liquid crystal layer and is capable of switching radio wave transmission direction at high speed, and a driving method thereof.

[0005] One embodiment of the present invention is a radio wave reflecting element. This radio wave reflecting element includes a patch electrode, an insulating film, an auxiliary electrode, a liquid crystal layer, and a counter electrode. The insulating film is located on the patch electrode. The auxiliary electrode is located on the insulating film and has at least one slit or notch that overlaps with the patch electrode. The liquid crystal layer is located on the auxiliary electrode, and the counter electrode is located on the liquid crystal layer. The patch electrode and the auxiliary electrode are configured so that variable potentials can be applied independently.

[0006] One embodiment of the present invention is a radio wave reflecting device. The radio wave reflecting device includes a plurality of radio wave reflecting elements arranged in a matrix shape having a plurality of rows and a plurality of columns. Each of the plurality of radio wave reflecting elements includes a patch electrode, an insulating film, an auxiliary electrode, a liquid crystal layer, and a counter electrode. The insulating film is located on the patch electrode. The auxiliary electrode is located on the insulating film and has at least one slit or notch that overlaps with the patch electrode. The liquid crystal layer is located on the auxiliary electrode. The counter electrode is located on the liquid crystal layer and is shared by the plurality of radio wave reflecting elements. The patch electrode and the auxiliary electrode are configured so that variable potentials can be applied to them individually.

[0007] One embodiment of the present invention is an antenna. The antenna includes an antenna electrode and a phase shifter. The phase shifter includes a microstrip line, an insulating film, an auxiliary electrode, a liquid crystal layer, and a counter electrode. The microstrip line is in the same layer as the antenna electrode. The insulating film is located on the microstrip line. The auxiliary electrode is located on the insulating film and has at least one slit or notch that overlaps with the microstrip line. The liquid crystal layer is located on the auxiliary electrode, and the counter electrode is located on the liquid crystal layer. The antenna electrode is electrically insulated from the microstrip line via the insulating film.

[0008] One embodiment of the present invention is a phased array antenna. The phased array antenna has a plurality of antennas. Each of the plurality of antennas includes an antenna electrode and a phase shifter. The phase shifter includes a microstrip line, an insulating film, an auxiliary electrode, a liquid crystal layer, and a counter electrode. The microstrip line is present in the same layer as the antenna electrode. The insulating film is located on the microstrip line. The auxiliary electrode is located on the insulating film and has at least one slit or notch that overlaps with the microstrip line. The liquid crystal layer is located on the auxiliary electrode, and the counter electrode is located on the liquid crystal layer. The antenna electrode is electrically insulated from the microstrip line via the insulating film.

[0009] 1 is a schematic top view of a radio wave reflecting device according to one embodiment of the present invention. 2 is a schematic top view of a radio wave reflecting element according to one embodiment of the present invention. 3 is a schematic end view of a radio wave reflecting element according to one embodiment of the present invention. 4 is a schematic end view of a radio wave reflecting element according to one embodiment of the present invention. 5 is a schematic top view of a radio wave reflecting element according to one embodiment of the present invention. 6 is a schematic end view of a radio wave reflecting element according to one embodiment of the present invention. 7 is a schematic end view of a radio wave reflecting element according to one embodiment of the present invention. 8 is a schematic diagram of a timing chart of a radio wave reflecting device according to one embodiment of the present invention. 9 is a schematic end view of a radio wave reflecting device according to one embodiment of the present invention. 10 is a schematic end view of a radio wave reflecting device according to one embodiment of the present invention. 11 is a schematic diagram of a driving method of a radio wave reflecting device according to one embodiment of the present invention. 12 is a schematic diagram of a driving method of a radio wave reflecting device according to one embodiment of the present invention. 13 is a schematic diagram of a driving method of a radio wave reflecting device according to one embodiment of the present invention. 14 is a schematic diagram of a phased array antenna according to one embodiment of the present invention. 15 is a schematic top view of an antenna according to one embodiment of the present invention. 16 is a schematic end view of an antenna according to one embodiment of the present invention. 1 is a schematic end view of an antenna according to an embodiment of the present invention; 2 is a schematic end view of an antenna according to an embodiment of the present invention; 3 is a schematic end view of an antenna according to an embodiment of the present invention; 4 is an example of a timing chart of an antenna according to an embodiment of the present invention; 5 is a schematic diagram illustrating a method for driving a radio wave reflecting device according to an embodiment of the present invention; 6 is a schematic diagram illustrating a method for driving a radio wave reflecting device according to an embodiment of the present invention;

[0010] Hereinafter, various embodiments of the present invention will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the spirit of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0011] In order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each drawing, elements having the same function as those described in the previous drawings may be assigned the same reference numerals, and duplicate explanations may be omitted. When multiple identical or similar components are collectively referred to, this reference numeral is used, and when these multiple components are individually referred to, a hyphen and a natural number are used after the reference numeral. Furthermore, when referring to a part of one component, a lowercase alphabet is used after the reference numeral.

[0012] In this specification and claims, when expressing an aspect of placing another structure on top of a certain structure, the term "on top" is used, unless otherwise specified, to include both a case where another structure is placed directly on top of a certain structure so as to be in contact with the certain structure, and a case where another structure is placed above a certain structure via yet another structure.

[0013] In this specification and claims, the expression "a structure exposed from another structure" means a state in which a part of a structure is not covered by another structure, and includes a state in which the part not covered by another structure is covered by yet another structure. The state expressed by this expression also includes a state in which a structure is not in contact with another structure.

[0014] In the present invention, when a single film is processed to form multiple films, these multiple films may have different functions and roles. However, these multiple films originate from films formed as the same layer in the same process, and have substantially the same layer structure, the same material, and the same morphology. Therefore, these multiple films are defined as existing in the same layer.

[0015] In this specification and claims, the expression that two structures are "orthogonal" includes not only a state in which the two structures intersect perpendicularly (90°) but also a state in which the two structures intersect at an angle of 90°±10°. Similarly, the expression that two structures are "parallel" includes not only a case in which the angle between the extension directions of the two structures is 0° but also a case in which the angle is 0°±10°.

[0016] First Embodiment Hereinafter, a radio wave reflecting element according to one embodiment of the present invention, a radio wave reflecting device including the same, and a method for driving the radio wave reflecting device will be described.

[0017] 1. Radio Wave Reflection Device (1) Overall Structure of the Radio Wave Reflection Device The radio wave reflection device, which is one embodiment of the present invention, is a so-called liquid crystal metasurface reflector, 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 wavelength frequency that can be reflected, for example, in the range of 400 MHz to 50 GHz. Typically, this radio wave reflection device 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.

[0018] FIG. 1 shows a schematic top view of a radio wave reflecting device 100. The radio wave reflecting device 100 includes a substrate 102 and an opposing substrate (not shown in FIG. 1 ), with various patterned insulating films, semiconductor films, conductive films, liquid crystal layers, and the like disposed between them. By appropriately stacking these films, a plurality of radio wave reflecting elements 120 are formed, arranged in a matrix shape having a plurality of rows and a plurality of columns. In addition to the radio wave reflecting elements 120, the radio wave reflecting device 100 also includes a scanning line driving circuit 106 for supplying scanning signals to the radio wave reflecting elements 120, and a signal line driving circuit 108 for supplying control signals. The scanning line driving circuit 106 and the signal line driving circuit 108 may be formed of insulating films, semiconductor films, or conductive films formed on the substrate 102, or may be formed by mounting an integrated circuit formed on a semiconductor substrate on the substrate 102. The number of the scanning line driving circuit 106 and the signal line driving circuit 108 may each be one or more. 1, two scanning line driving circuits 106 may be arranged on the substrate 102 so as to sandwich a plurality of radio wave reflecting elements 120. The signal line driving circuit 108 is arranged on one side of the substrate 102.

[0019] Although not shown in Fig. 1, a plurality of scanning lines (hereinafter referred to as gate lines) and a plurality of signal lines extend from the scanning line driving circuit 106 and the signal line driving circuit 108, respectively, and are electrically connected to the radio wave reflecting element 120. Therefore, the radio wave reflecting element 120 is electrically connected to the corresponding gate lines and signal lines. A plurality of terminals 110 are further provided on the substrate 102, and various signals for driving the radio wave reflecting element 120 are supplied via the terminals 110 from an external circuit (not shown). The scanning line driving circuit 106 and the signal line driving circuit 108 generate scanning signals and control signals, respectively, based on the supplied signals and supply them to the radio wave reflecting element 120.

[0020] (2) Structure of the Radio Wave Reflecting Element Fig. 2 shows a schematic top view of one radio wave reflecting element 120, and Figs. 3 and 4 show schematic views of the end faces along the chain lines A-A' and B-B' in Fig. 2. Fig. 2 shows part of the configuration of the radio wave reflecting elements 120 adjacent in the column direction (the second gate line 116-2 and the first gate line 116-1).

[0021] 2, the radio wave reflecting device 100 has two gate lines (a first gate line 116-1 and a second gate line 116-2) for supplying scanning signals to the radio wave reflecting elements 120 arranged in each of a plurality of rows, and a signal line 118 for supplying control signals to the radio wave reflecting elements 120 arranged in each of a plurality of columns. The first gate line 116-1 and the second gate line 116-2 extend in the row direction, and the signal line 118 extends in the column direction. That is, the signal line 118 intersects with the first gate line 116-1 and the second gate line 116-2.

[0022] Each radio wave reflecting element 120 includes at least two transistors (a first transistor 140 and a second transistor 150), and a portion of each of the first gate line 116-1 and the second gate line 116-2 constitutes the gate electrodes of the first transistor 140 and the second transistor 150. In other words, the first transistor 140 and the second transistor 150 are connected to different gate lines, i.e., the first gate line 116-1 and the second gate line 116-2, respectively. Therefore, the first gate line 116-1 is electrically connected to the gate electrodes of the first transistors 140 of the plurality of radio wave reflecting elements 120 provided in the row in which it is arranged. On the other hand, the second gate line 116-2 is electrically connected to the gate electrodes of the second transistors 150 of the plurality of radio wave reflecting elements 120 provided in the row in which it is arranged. A potential is individually supplied to the first gate line 116-1 and the second gate line 116-2 by the scanning line driving circuit 106. Therefore, in each radio wave reflecting element 120, the first transistor 140 and the second transistor 150 can be driven and controlled independently of each other.

[0023] In each row, a part of the signal line 118 functions as a terminal 146 of the first transistor 140, and another part functions as a terminal 156 of the second transistor 150 (see FIGS. 3 and 4). Therefore, when focusing on one radio wave reflecting element 120, the signal line 118 is electrically connected to the first transistor 140 and the second transistor 150 of this radio wave reflecting element 120, and is also electrically connected to the first transistor 140 and the second transistor 150 of each of the radio wave reflecting elements 120 in the same column as this radio wave reflecting element 120.

[0024] For this reason, the number of gate lines 116 is doubled compared to a normal liquid crystal display device, but generally, the number of radio wave reflecting elements provided in a radio wave reflecting device is significantly smaller than the number of pixels provided in a liquid crystal display device, so the load on the scanning line driving circuit 106 is small. Therefore, all of the radio wave reflecting elements 120 can be switched on and off at high speed by the scanning line driving circuit 106.

[0025] 3 and 4, the first transistor 140 and the second transistor 150 are provided on the substrate 102 directly or via an undercoat 122 having an optional configuration. In the example shown in FIGS. 2 and 3, the first transistor 140 is composed of a gate electrode 142, a gate insulating film 124 on the gate electrode 142, a semiconductor film 144 located on the gate insulating film 124 and overlapping with the gate electrode 142, and terminals 146 and 148 electrically connected to the semiconductor film 144. Similarly, the second transistor 150 is composed of a gate electrode 152, a gate insulating film 124 on the gate electrode 152, a semiconductor film 154 located on the gate insulating film 124 and overlapping with the gate electrode 152, and terminals 156 and 158 electrically connected to the semiconductor film 154. 2 to 4, both the first transistor 140 and the second transistor 150 have a bottom-gate structure, but there are no restrictions on these structures, and the first transistor 140 and the second transistor 150 may have a top-gate structure, or may have gate electrodes above and below the semiconductor film. There are also no restrictions on the vertical relationship between the terminals 146 and 148 and the semiconductor film 144, and the former may be located below the latter. The same applies to the vertical relationship between the terminals 156 and 158 and the semiconductor film 154.

[0026] A planarization film 128 for absorbing unevenness resulting from the first transistor 140 and the second transistor 150 and providing a flat surface is provided over the first transistor 140 and the second transistor 150. As an optional configuration, a first interlayer insulating film 126 may be provided between the first transistor 140, the second transistor 150, and the planarization film 128.

[0027] The above-described configuration can be formed by appropriately employing known structures and materials, and therefore detailed description thereof will be omitted. Briefly, the substrate 102 may contain an inorganic insulator such as glass or quartz, a semiconductor such as silicon, a polymer such as polyimide, polycarbonate, or polyester, or a metal such as aluminum, copper, or stainless steel. When a conductive material such as metal is included, it is preferable to provide an undercoat 122 on the surface on which the radio wave reflecting element 120 is provided, i.e., on the surface of the substrate 102 facing the opposing substrate 104. The substrate 102 may or may not be transparent to visible light. The substrate 102 may also be flexible. The undercoat 122, gate insulating film 124, first interlayer insulating film 126, and the like may be formed of one or more layers containing a silicon-containing inorganic compound such as silicon oxide or silicon nitride. The gate insulating film 124 may be configured to contain a so-called high-k material such as hafnium silicate, nitrogen-containing hafnium silicate, hafnium oxide, nitrogen-doped hafnium aluminate, or yttrium oxide. The gate line 116, signal line 118, gate electrodes 142, 152, and terminals 146, 148, 156, and 158 may be configured to contain a metal such as titanium, molybdenum, tungsten, copper, or aluminum, or an alloy containing a metal selected from these. The semiconductor films 144 and 154 may contain a Group 14 element such as silicon, or may be formed as a film containing an oxide of a Group 13 element such as indium or gallium. The planarization film 128 may be configured to contain a polymer such as polyimide, polyamide, acrylic resin, or silicone resin.

[0028] Although only the first transistor 140 and the second transistor 150 are shown between the planarization film 128 and the substrate 102 in Figures 2 to 4, each radio wave reflecting element 120 may further include various elements such as one or more transistors and one or more capacitive elements.

[0029] A liquid crystal element 160 is provided on the planarization film 128. The liquid crystal element 160 basically comprises a first electrode (hereinafter referred to as a patch electrode) 162, a second electrode (hereinafter referred to as an auxiliary electrode) 166, a second interlayer insulating film 164, a first alignment film 168, a second alignment film 172, a liquid crystal layer 170, and a counter electrode 174.

[0030] The patch electrode 162 is electrically connected to one terminal 148 of the first transistor 140 through an opening provided in the planarizing film 128 and the first interlayer insulating film 126. As a result, when the first transistor 140 is turned on, a control signal is applied to the patch electrode 162 from the signal line 118 through the terminal 146, the semiconductor film 144, and the terminal 148. On the other hand, the auxiliary electrode 166 is electrically connected to one terminal 158 of the second transistor 150 through an opening provided in the planarizing film 128, the first interlayer insulating film 126, and the second interlayer insulating film 164. As a result, when the second transistor 150 is turned on, a control signal is applied to the auxiliary electrode 166 from the signal line 118 through the terminal 156, the semiconductor film 154, and the terminal 158. Therefore, by appropriately switching on and off the first transistor 140 and the second transistor 150, it is possible to supply any potential (i.e., a variable potential) to the patch electrode 162 and the auxiliary electrode 166. The patch electrode 162 and the auxiliary electrode 166 may be configured to include the above-mentioned metal or alloy, or may include a conductive oxide exhibiting light transmission, such as indium-tin oxide (ITO) or indium-zinc oxide (IZO).

[0031] Although there are no restrictions on the shape (planar shape) of the patch electrode 162, it is preferable that the patch electrode 162 has a shape with multiple intersecting symmetry axes, such as a regular polygon including a square. By adopting such a shape, it is possible to efficiently reflect both vertically polarized and horizontally polarized radio waves that are incident.

[0032] Here, the auxiliary electrode 166 has at least one, preferably multiple, slits 166a. The slits 166a overlap the patch electrode 162, so that a portion of the patch electrode 162 is exposed through the auxiliary electrode 166. The length and width of the slits 166a are appropriately selected depending on the frequency of the reflected radio waves. For example, the length is 2 mm to 100 mm or 2 mm to 30 mm, and the width is 1 μm to 100 μm or 1 μm to 10 μm. Therefore, the aspect ratio (length / width) of the slits 166a also depends on the frequency of the reflected radio waves and is, for example, 10 to 10,000. The number of slits 166a provided in each auxiliary electrode 166 is also appropriately selected depending on the frequency of the radio waves. Note that in the example shown in FIG. 2, the slits 166a extend linearly, but each slit 166a may have one or more bends. Here, a slit is an opening provided in the film, the outline of which has a closed shape and is independent from the outermost periphery of the film.

[0033] Alternatively, as shown in FIG. 5 , the auxiliary electrode 166 may have one or more notches 166b instead of the slits 166a. Therefore, the auxiliary electrode 166 may have a comb-like shape. Here, a notch is an apparent defect provided in the film, has an open outline, and constitutes part of the outermost periphery of the film. The notches 166b are located between adjacent comb teeth, and the patch electrode 162 is exposed at the notches 166b. The length, width, and aspect ratio of the notches 166b may also be set appropriately within the above-mentioned ranges for the length, width, and aspect ratio of the slits 166a.

[0034] The second interlayer insulating film 164 is sandwiched between the patch electrode 162 and the auxiliary electrode 166 and is provided to electrically insulate them from each other. Therefore, the second interlayer insulating film 164 may also be composed of one or more films containing, for example, a silicon-containing inorganic compound.

[0035] The first alignment film 168 and the second alignment film 172 are both provided to cover the patch electrode 162 and the auxiliary electrode 166 and to sandwich the liquid crystal layer 170. The first alignment film 168 and the second alignment film 172 are provided to control the alignment of liquid crystal molecules constituting the liquid crystal layer 170 therebetween. The first alignment film 168 and the second alignment film 172 can be provided continuously across a plurality of radio wave reflecting elements 120. In other words, the first alignment film 168 and the second alignment film 172 can be provided so as to be shared by all of the radio wave reflecting elements 120 without being divided between adjacent radio wave reflecting elements 120.

[0036] Both the first alignment film 168 and the second alignment film 172 contain a polymer such as polyimide or polyester. The first alignment film 168 and the second alignment film 172 are formed using a wet film formation method such as an inkjet method, a spin coating method, a printing method, or a dip coating method, and their surfaces are subjected to a rubbing treatment. Alternatively, the first alignment film 168 and the second alignment film 172 may be formed by a photo-alignment treatment. By using the rubbing treatment or the photo-alignment treatment, the first alignment film 168 and the second alignment film 172 can align the liquid crystal molecules in a uniform direction along the major surfaces of the substrate 102 and the counter substrate 104. Therefore, when no electric field is present in the liquid crystal layer 170, the liquid crystal molecules are homogeneously aligned, with their long axis direction being approximately parallel to the major surface of the substrate 102. The directions (alignment directions) in which the first alignment film 168 and the second alignment film 172 align the liquid crystal molecules can be set arbitrarily, and may be parallel or perpendicular to the longitudinal direction of the slit 166 a or the notch 166 b, or may be tilted at any angle from the longitudinal direction. Furthermore, the alignment directions of the first alignment film 168 and the second alignment film 172 may be the same or different. For example, the alignment directions of the first alignment film 168 and the second alignment film 172 may be perpendicular to each other.

[0037] The liquid crystal layer 170 includes liquid crystal molecules. The structure of the liquid crystal molecules is not limited. Therefore, the liquid crystal molecules may be nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, or chiral smectic liquid crystal. The thickness of the liquid crystal layer 170 is, for example, 20 μm to 100 μm, or 30 μm to 50 μm. Although not shown, spacers may be provided within the liquid crystal layer 170 to maintain this thickness throughout the entire radio wave reflecting device 100.

[0038] The counter electrode 174 can be provided as a single electrode integrated across multiple radio wave reflecting elements 120 so as to be shared by the multiple radio wave reflecting elements 120. Therefore, the counter electrode 174 is also referred to as a common electrode. Because the radio wave reflecting elements 120 may or may not transmit visible light, the counter electrode 174 may also contain the above-mentioned metals or alloys, or conductive oxides such as ITO or IZO, similar to the patch electrode 162 and auxiliary electrode 166. A constant common potential is supplied to the counter electrode 174 directly from an external circuit (not shown) or via the signal line driving circuit 108. A potential difference between the counter electrode 174 and the patch electrode 162 and / or between the counter electrode 174 and the auxiliary electrode 166 generates a vertical electric field in the liquid crystal layer 170. This vertical electric field changes the orientation of the liquid crystal molecules, thereby controlling the dielectric constant of the liquid crystal layer 170.

[0039] Here, the distance D between the patch electrode 162 and the auxiliary electrode 166 is ２ (the distance from the upper surface of the patch electrode 162 to the lower surface of the auxiliary electrode 166) is the distance D between the auxiliary electrode 166 and the counter electrode 174 １ The liquid crystal element 160 is configured so that the distance D is smaller than the distance from the upper surface of the auxiliary electrode 166 to the lower surface of the counter electrode 174. ２ is determined mainly by the second interlayer insulating film 164 and is, for example, 50 nm or more and 5 μm or less. １ is mainly determined by the liquid crystal layer 170, the first alignment film 168, and the second alignment film 172. For example, the distance D ２ is the distance D １ Alternatively, the value may be set within a range of 100 times or more and 1000 times or less, or 100 times or more and 500 times or less.

[0040] The counter substrate 104 can have a similar configuration to the substrate 102. The substrate 102 and the counter substrate 104 are sealed by a sealant 112 (FIG. 1), and the liquid crystal layer 170 is sealed in the space created by the sealant 112, the substrate 102, and the counter substrate 104. As shown in FIGS. 3 and 4 , an undercoat 130 may be provided on the surface of the counter substrate 104 facing the liquid crystal layer 170 to prevent impurities in the counter substrate 104 from diffusing toward the liquid crystal layer 170. The undercoat 130 can also have a similar configuration to the undercoat 122.

[0041] 2. Driving Method of Radio Wave Reflecting Device The driving method of the radio wave reflecting device 100 will be described below with reference to FIGS. 6 to 12. FIG. 6 is an example of a timing chart for driving the radio wave reflecting device 100, which schematically shows the potential changes applied to the counter electrode 174, patch electrode 162, and auxiliary electrode 166 for one radio wave reflecting element 120 over seven consecutive frames. FIGS. 7 to 9 are schematic end views of a portion of one radio wave reflecting element 120, and FIGS. 10 to 12 are schematic end views of multiple radio wave reflecting elements 120. For ease of viewing, these figures only show a portion of the configuration; for example, FIGS. 10 to 12 show only the patch electrode 162, auxiliary electrode 166, liquid crystal layer 170, and counter electrode 174. In FIGS. 7 to 9, liquid crystal molecules are schematically represented by ellipses.

[0042] According to the timing chart of FIG. 6 , the radio wave reflecting device 100 is in an off state in the first, fourth, and seventh frames. In contrast, the radio wave reflecting device 100 is in an on state in the second and fifth frames, and an electric field is formed in the liquid crystal layer 170. As a result, the reflection direction of the incident radio wave is controlled in the second and fifth frames. In the example shown here, the electric field strength formed in the liquid crystal layer 170 in the second and fifth frames is different from that in the fifth frame, with the latter being stronger than the former. The third and sixth frames are also called overdrive periods, and as will be described later, providing these frames enables high-speed switching of the radio wave reflection direction.

[0043] (1) Off State In the first frame, the same potential is applied to the patch electrode 162, auxiliary electrode 166, and counter electrode 174 in all radio wave reflecting elements 120. Here, this potential is described as the ground potential (0 V), but the potentials applied to the patch electrode 162, auxiliary electrode 166, and counter electrode 174 are relative to an arbitrarily determined potential. In this state, these electrodes are at the same potential, no electric field is generated in the liquid crystal layer 170, and the liquid crystal molecules in the liquid crystal layer 170 are homogeneously aligned according to the alignment directions of the first alignment film 168 and the second alignment film 172 ( FIG. 7 ). As a result, the dielectric constant of the liquid crystal layer 170 is the same across all radio wave reflecting elements 120. 10 which is a schematic end view of a plurality of radio wave reflecting elements 120, there is no change in the spread (phase) of the reflected wave generated when radio waves incident from the patch electrode 162 side (solid white arrow in FIG. 10) are reflected on the surface of the counter electrode 174. Therefore, the incident radio waves are specularly reflected by the radio wave reflecting device 100, and a reflected wave (dotted white arrow in FIG. 10) having the same angle of emission as the angle of incidence is generated.

[0044] (2) ON state In the second frame following the first frame, the radio wave reflecting element 120 is turned ON. Specifically, the potential V ０ is kept at 0V, in each radio wave reflecting element 120, the first transistor 140 is turned on while the second transistor 150 is kept off, and in this state, an arbitrary potential (here, a potential of +aV) different from the ground potential is supplied from the signal line 118 to the patch electrode 162. As a result, the potential V of the patch electrode 162 ｐ becomes +aV.

[0045] Then, the first transistor 140 is turned off. As a result, the potential V ｐ Next, while the first transistor 140 is maintained in the off state, the second transistor 150 is turned on, and in this state, an arbitrary potential (here, a potential of +aV) different from the ground potential is supplied from the signal line 118. As a result, the potential V of the auxiliary electrode 166 ａ Gaa １In the above description, the potential V of the patch electrode 162 ｐ After setting the potential V of the auxiliary electrode 166 ａ However, the order of these is arbitrary. ｐ and the potential V of the auxiliary electrode 166 ａ may be the same or different from each other, but it is preferable that the potentials of these electrodes are the same so that a potential difference between the patch electrode 162 and the auxiliary electrode 166 does not generate a transverse electric field.

[0046] The above operation generates a potential difference between the patch electrode 162 and the counter electrode 174, and between the auxiliary electrode 166 and the counter electrode 174, which generates a vertical electric field in the liquid crystal layer 170 (see the dotted arrows in FIG. 8). ｐ and the potential V of the auxiliary electrode 166 ａ is determined by the reflection direction of the incident wave. The phase change of the reflected wave depends on the change in the dielectric constant of the liquid crystal layer 170, and the greater the change in the dielectric constant, the greater the phase change. The change in the dielectric constant also depends on the strength of the electric field generated in the liquid crystal layer 170. Therefore, when the phase of the reflected wave is to be changed significantly, the potential V of the counter electrode 174 ｏ This can be achieved by applying a potential that is significantly different from the above to the patch electrode 162 and the auxiliary electrode 166 .

[0047] When a longitudinal electric field is generated, the liquid crystal molecules rise, and the direction of their long axes approaches the direction of the electric field, resulting in a bend alignment, a homeotropic alignment, or a similar alignment, depending on the field strength. As a result, the dielectric constant of the liquid crystal layer 170 changes due to the dielectric anisotropy of the liquid crystal molecules. Therefore, by changing the strength of the longitudinal electric field for each radio wave reflecting element 120, the phase of the reflected wave for each radio wave reflecting element 120 can be changed (see FIG. 11). As a result, as shown by the straight line in FIG. 11, the equiphase surface of the reflected wave can be tilted, i.e., the reflection direction of the incident radio wave (solid white arrow in FIG. 11) can be changed (see dotted white arrow in FIG. 11).

[0048] Depending on the inclination of the phase surface, there may be radio wave reflecting elements 120 in which the phase change of the reflected wave exceeds 360°. In this case, the potential of the patch electrode 162 is controlled so that the electric field generated in the liquid crystal layer 170 changes periodically. Specifically, as shown in FIG. 12 , by driving the radio wave reflecting device 100 so that the longitudinal electric field in the liquid crystal layer 170 changes periodically in the row direction or column direction, one unit period is formed that includes a plurality of radio wave reflecting elements 120 in which the longitudinal electric field strength continuously increases or decreases in the row direction or column direction. In each unit period, the longitudinal electric field strength is adjusted so that one equiphase surface represented by a solid straight line is formed. In the example shown in FIG. 12 , the phase change in one unit period is continuously θ １ , θ ２ , θ ３ (θ １ <θ ２ <θ ３ ) changes. In addition, the radio wave reflecting device 100 is driven so that the phase difference between the equiphase surfaces between adjacent unit periods is 360°. By driving the radio wave reflecting device 100 in this way, a comprehensive equiphase surface represented by the dotted straight line can be obtained, and it becomes possible to change the reflection direction of the incident radio waves (solid white arrow in FIG. 12 ) (see dotted white arrow in FIG. 12 ).

[0049] Thereafter, when the radio wave reflecting element 120 is returned to the OFF state, in the third frame, the potential V ｏ is set to 0 V, and the potential V ｐ While maintaining the potential V of the auxiliary electrode 166 at +aV, ａ 9, a transverse electric field is generated between the patch electrode 162 and the auxiliary electrode 166. Meanwhile, a potential difference still exists between the patch electrode 162 and the counter electrode 174, but as described above, the distance D ２ Compared to the distance D １is so large that the vertical electric field can be ignored compared to this horizontal electric field. As a result, in the third frame, the liquid crystal molecules that stood up in the second frame can be forcibly returned to their original homogeneous orientation by utilizing the horizontal electric field. The contribution of the driving force due to this horizontal electric field allows the orientation of the liquid crystal layer 170 to be quickly returned to its original state. Thereafter, in the fourth frame, the potential V of the patch electrode 162 ｐ is returned to the initial potential (0 V), the state transitions to the OFF state.

[0050] After this, when transitioning to the ON state (fifth frame) which causes an even greater change in the dielectric constant, a larger potential (in the example of FIG. 6 , a potential of +bV, where b>a) can be applied to the patch electrode 162 and the auxiliary electrode 166, respectively. The same applies when transitioning to the OFF state again after this; in the sixth frame following the fifth frame, no potential difference is applied between the auxiliary electrode 166 and the counter electrode 174, but a potential difference is applied between the auxiliary electrode 166 and the patch electrode 162 to form a transverse electric field. This allows the alignment state of the liquid crystal layer 170 to be quickly returned to a homogeneous alignment.

[0051] In the above example, in consecutive frames in the ON state (here, the second frame and the fifth frame), the potential V ｐ and V ａ The polarity of the potential V of the counter electrode 174 ｏ , but the potential V of the patch electrode 162 and auxiliary electrode 166 between successive ON-state frames is the same. ｐ and V ａ By adopting such a so-called inversion driving, burn-in of the liquid crystal layer 170 can be prevented.

[0052] As described above, in the radio wave reflecting device 100 according to one embodiment of the present invention, the thickness of the liquid crystal layer 170 is much larger than that of a liquid crystal display device. Therefore, the liquid crystal response speed is slow and high-speed switching is not possible when using a driving method similar to that used in liquid crystal display devices, such as IPS (In-Plane Switching) liquid crystal display devices. This is because only the van der Waals forces between the liquid crystal molecules and the first alignment film 168 and the second alignment film 172 can be utilized to return the liquid crystal molecules to a homogeneous alignment. In contrast, in the radio wave reflecting device 100 according to one embodiment of the present invention, when returning the liquid crystal molecules aligned using a vertical electric field to a homogeneous alignment, the van der Waals forces and the horizontal electric field between the auxiliary electrode 166 and the patch electrode 162 can be utilized. This allows the homogeneous alignment to be quickly restored, thereby enabling the reflection characteristics of the radio wave reflecting device 100 to be switched at high speed. Therefore, by applying one embodiment of the present invention, a radio wave reflecting device capable of quickly changing the radio wave reflection direction can be provided.

[0053] 3. Modification In the configuration described above, two gate lines 116 are arranged in each row, and these individually control the first transistor 140 and the second transistor 150. Meanwhile, in each of the multiple radio wave reflecting elements 120 arranged in each column, the first transistor 140 and the second transistor are both electrically connected to the same signal line 118. Therefore, a potential is supplied to the patch electrode 162 and the auxiliary electrode 166 from the common signal line 118.

[0054] The configuration of the radio wave reflecting device 100 according to one embodiment of the present invention is not limited to the above-described configuration and various modifications are possible. For example, as shown in FIG. 13 , one gate line 116 may be provided in each row, and two signal lines (a first signal line 118-1 and a second signal line 118-2) may be provided in each column. The first signal line 118-1 and the second signal line 118-2 extend in the column direction. In each row, portions of the first signal line 118-1 and the second signal line 118-2 respectively constitute the terminals 146, 156 of the first transistor 140 and the second transistor 150. In other words, the first transistor 140 and the second transistor 150 are connected to different signal lines, i.e., the first signal line 118-1 and the second signal line 118-2. Therefore, the first signal line 118-1 is electrically connected to the terminals 146 of the first transistors of the multiple radio wave reflecting elements 120 arranged in the column in which it is arranged. On the other hand, the second signal line 118-2 is electrically connected to the terminals 156 of the second transistors 150 of the plurality of radio wave reflecting elements 120 arranged in the same column as the second signal line 118-2. The first signal line 118-1 and the second signal line 118-2 are individually controlled by the signal line drive circuit 108, and variable potentials are supplied to them. Therefore, in each radio wave reflecting element 120, any potential can be supplied to the first transistor 140 and the second transistor 150 from the first signal line 118-1 and the second signal line 118-2, respectively.

[0055] The gate line 116 extends in the row direction and intersects with the first signal line 118-1 and the second signal line 118-2. In each column, a part of the gate line 116 functions as the gate electrode 142 of the first transistor 140, and another part functions as the gate electrode 152 of the second transistor 150. Therefore, when focusing on one radio wave reflecting element 120, the gate line 116 is electrically connected to the first transistor 140 and the second transistor 150 of this radio wave reflecting element 120, and is also electrically connected to the first transistor 140 and the second transistor 150 of each radio wave reflecting element 120 on the same row as this radio wave reflecting element 120. Therefore, in each row, the first transistor and the second transistor are driven simultaneously.

[0056] 2, in this modified example, the number of signal lines 118 is twice as many as in a normal liquid crystal display device, but the number of radio wave reflecting elements provided in the radio wave reflecting device is significantly smaller than the number of pixels provided in the liquid crystal display device, so the load on the signal line driving circuit 108 is small. Therefore, all of the radio wave reflecting elements 120 can be switched on and off at high speed, and corresponding control signals can be supplied.

[0057] In this modification as well, by appropriately selecting the potentials supplied via the first signal line 118-1 and the second signal line 118-2 during the overdrive period, a transverse electric field can be formed between the patch electrode 162 and the auxiliary electrode 166. This allows the liquid crystal molecules that stand up when the switch is turned on to quickly return to a homogeneous orientation, thereby enabling high-speed switching of the radio wave reflection direction.

[0058] Second Embodiment In this embodiment, an antenna according to one embodiment of the present invention, a phased array antenna including the antenna, and a method for driving the phased array antenna will be described. Descriptions of configurations that are the same as or similar to the configuration described in the first embodiment may be omitted.

[0059] 1. Phased Array Antenna (1) Overall Structure of Phased Array Antenna A phased array antenna is a plurality of antennas arranged in a line or a circle, and by adjusting the phase of the AC signal supplied to each antenna, it is possible to transmit radio waves with strong directionality in any direction. There are no restrictions on the wavelength of radio waves that can be transmitted by a phased array antenna according to one embodiment of the present invention, and the wavelength ranges from 400 MHz to 50 GHz, for example. Typically, this phased array antenna can be used to transmit 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.

[0060] A schematic top view of the phased array antenna 200 is shown in Figure 14. As shown in Figure 14, the phased array antenna 200 has a substrate 202 and an opposing substrate (not shown in Figure 14), with various patterned insulating films, semiconductor films, conductive films, liquid crystal layers, etc. disposed between them. By appropriately stacking these films, multiple antennas 210, as well as drive circuits 206 for driving each antenna 210 and transmission wiring 208 for transmitting AC signals to the antennas 210, are formed. Multiple terminals (not shown) are formed on the substrate 202, and various signals are supplied to the drive circuit 206 from an external circuit (not shown) via the terminals. The drive circuit 206 generates signals (scanning signals and control signals) for driving each antenna 210 based on the supplied signals and supplies them to the antennas 210 via wiring (not shown in Figure 14). The substrate 202 and opposing substrate are fixed to each other by a sealant 212, and the multiple antennas 210, drive circuits 206, and transmission wiring 208 are protected by the substrate 202, opposing substrate, and sealant 212. A part of the transmission wiring 208 crosses the sealing material 212 and is exposed from the opposing substrate.

[0061] 14, the multiple antennas 210 are arranged in one direction, but there are no restrictions on the arrangement of the antennas 210. For example, the multiple antennas 210 may be arranged on a circumference, or may be arranged in a matrix shape having multiple rows and multiple columns.

[0062] (2) Antenna Structure Fig. 15 shows a schematic top view of one antenna 210, and Figs. 16 to 18 show schematic end views along chain lines CC', DD', and EE' in Fig. 15. As shown in these figures, the antenna 210 mainly comprises an antenna electrode 280, a phase shifter 220, and at least two transistors (a first transistor 240 and a second transistor 250) for driving the phase shifter 220.

[0063] The phase shifter 220 is disposed between the antenna electrode 280 and the transmission wiring 208. The transmission wiring 208 is a conductive film containing a metal such as molybdenum, tungsten, titanium, aluminum, or copper, or an alloy containing a metal selected from these, and receives an AC signal as input from a transmitter (not shown) and transmits this AC signal to the phase shifter 220 of each antenna 210 using capacitive coupling. In the example shown in Fig. 14, the transmission wiring 208 has a branched structure, with multiple branch ends reaching the vicinity of the corresponding phase shifters 220. Therefore, AC signals having the same phase and frequency are supplied to the phase shifters 220.

[0064] The phase shifter 220 is an element that has the function of changing the phase of an AC signal, and by changing the phase amount for each antenna 210, it is possible to give directionality to the radio waves emitted from the phased array antenna 200, and to emit radio waves in any direction.

[0065] The antenna electrode 280 is also a conductive film containing the above-mentioned metal or alloy, and utilizes capacitive coupling to transmit radio waves at a frequency corresponding to the AC signal input from the phase shifter 220. For this reason, the antenna electrode 280 preferably has a shape with multiple intersecting axes of symmetry, such as a regular polygon including a square. For example, although this depends on the frequency, the antenna electrode 280 may be arranged so as to have a square shape with one side measuring 2 mm to 30 mm.

[0066] 15 to 17 , the phased array antenna 200 has two gate lines (a first gate line 214-1 and a second gate line 214-2) for supplying scanning signals to the multiple antennas 210, as well as a signal line 216 for supplying control signals. The first gate line 214-1 and the second gate line 214-2 extend in the direction in which the multiple antennas 210 are arranged, and are electrically connected to all of the antennas 210. On the other hand, the signal lines 118 that intersect with the gate lines 214 are provided in the same number as the antennas 210, and are electrically connected to the corresponding antennas 210, respectively.

[0067] Each antenna 210 includes at least two transistors (a first transistor 240 and a second transistor 250) for driving the phase shifter 220, and a portion of the first gate line 214-1 and a portion of the second gate line 214-2 form the gate electrodes of the first transistor 240 and the second transistor 250, respectively. In other words, the first transistor 240 and the second transistor 250 are connected to different gate lines, i.e., the first gate line 214-1 and the second gate line 214-2. Therefore, the first gate line 214-1 is electrically connected to the gate electrodes of the first transistors 240 of all the antennas 210. On the other hand, the second gate line 214-2 is electrically connected to the gate electrodes of the second transistors 250 of all the antennas 210. A potential (scanning signal) is individually supplied to the first gate line 214-1 and the second gate line 214-2 by the drive circuit 206. Therefore, in each antenna 210, the first transistor 240 and the second transistor 250 can be driven and controlled independently of each other. Although the number of gate lines 214 is twice as many as that of a normal liquid crystal display device, the number of antennas provided in a phased array antenna is generally much smaller than the number of pixels provided in a liquid crystal display device, and therefore the load on the driver circuit 206 is small. Therefore, all of the antennas 210, more specifically, the phase shifters 220 included in the antennas 210, can be switched on and off at high speed.

[0068] A part of each signal line 216 functions as a terminal 246 of the first transistor 240, and another part functions as a terminal 256 of the second transistor 250 (see FIG. 15). Therefore, each signal line 216 is electrically connected to the first transistor 240 and the second transistor 250 of one antenna 210, and supplies an individual potential (i.e., a variable potential) to each transistor as a control signal.

[0069] 16 and 17 , a first transistor 240 and a second transistor 250 are provided on a substrate 202 directly or via an undercoat 222 having an arbitrary configuration. In the example shown in FIGS. 15 and 16 , the first transistor 240 is composed of a gate electrode 242, a gate insulating film 224 on the gate electrode 242, a semiconductor film 244 located on the gate insulating film 224 and overlapping with the gate electrode 242, and terminals 246 and 248 electrically connected to the semiconductor film 244. Similarly, the second transistor 250 is composed of a gate electrode 252, a gate insulating film 224 on the gate electrode 252, a semiconductor film 254 located on the gate insulating film 224 and overlapping with the gate electrode 252, and terminals 256 and 258 electrically connected to the semiconductor film 254. 15 to 17, both the first transistor 240 and the second transistor 250 have a bottom-gate structure, but there are no restrictions on these structures, and the first transistor 240 and the second transistor 250 may have a top-gate structure, or may have gate electrodes above and below the semiconductor film. There are also no restrictions on the vertical relationship between the terminals 246, 248 and the semiconductor film 244, and the former may be located below the latter. The same applies to the vertical relationship between the terminals 256, 258 and the semiconductor film 254.

[0070] A planarization film 228 is provided on the first transistor 240 and the second transistor 250 to absorb unevenness resulting from these and provide a flat surface. As an optional configuration, a first interlayer insulating film 226 may be provided between the first transistor 240, the second transistor 250, and the planarization film 228. Furthermore, each antenna 210 may further include various elements such as one or more transistors and one or more capacitor elements in addition to the first transistor 240 and the second transistor 250. The configuration from the substrate 102 to the planarization film 228 is similar to that of the first embodiment, and therefore further description will be omitted.

[0071] The phase shifter 220 is provided on the planarization film 228. The phase shifter 220 basically includes a microstrip line 260, a second interlayer insulating film 262, an auxiliary electrode 264, a first alignment film 266, a second alignment film 270, a liquid crystal layer 268, and a counter electrode 272.

[0072] The microstrip line 260 is electrically connected to one terminal 248 of the first transistor 240 through an opening provided in the planarization film 228 and the first interlayer insulating film 226. As a result, when the first transistor 240 is turned on, a control signal is applied to the microstrip line 260 from the signal line 216 via the terminal 246, the semiconductor film 244, and the terminal 248. The microstrip line 260 is an electrode with a large aspect ratio (e.g., length / width ratio of 2 to 500), and in the examples shown in FIGS. 14 and 15 , its longitudinal direction is arranged perpendicular to the arrangement direction of the multiple antennas 210. The length of the microstrip line 260 may be set to, for example, 1 mm to 10 mm, and the width to 20 μm to 500 μm. The microstrip line 260 is configured to include a metal such as molybdenum, tungsten, titanium, aluminum, or copper, or an alloy containing a metal selected from these.

[0073] 18 , the microstrip line 260 can be disposed so as to be present in the same layer as the antenna electrode 280 and the transmission wiring 208. Therefore, the microstrip line 260, the antenna electrode 280, and the transmission wiring 208 can have the same composition and thickness. The microstrip line 260, the antenna electrode 280, and the transmission wiring 208 are spaced apart from one another and electrically insulated by a second interlayer insulating film 262. The distance between the microstrip line 260 and the antenna electrode 280 and the distance between the microstrip line 260 and the transmission wiring 208 may be set to, for example, 1 μm or more and 20 μm or less.

[0074] Meanwhile, the auxiliary electrode 264 is electrically connected to one terminal 258 of the second transistor 250 through openings provided in the planarizing film 228, the first interlayer insulating film 226, and the second interlayer insulating film 262. As a result, when the second transistor 150 is turned on, a control signal is applied to the auxiliary electrode 264 from the signal line 216 via the terminal 256, the semiconductor film 254, and the terminal 258. Therefore, by appropriately switching the first transistor 240 and the second transistor 250 on and off, a desired potential (i.e., a variable potential) can be supplied to the microstrip line 260 and the auxiliary electrode 264. The auxiliary electrode 264 may also be configured to include the above-mentioned metal or alloy, or may include a transparent conductive oxide such as ITO or indium-zinc oxide (IZO). The microstrip line 260 and the auxiliary electrode 264 are electrically insulated by the second interlayer insulating film 262 located therebetween. The second interlayer insulating film 262 may also be made of one or more films containing a silicon-containing inorganic compound.

[0075] Here, the auxiliary electrode 264 has at least one, preferably multiple, notches 264a ( FIG. 15 ). In other words, the auxiliary electrode 264 may have a comb-like shape. The notches 264a overlap the microstrip line 260, so that a portion of the microstrip line 260 is exposed from the auxiliary electrode 264. While depending on the frequency, for example, the length of the notch 264a is 10 μm to 400 μm, the width is 1 μm to 100 μm, and the aspect ratio (length / width) is 2 to 400. The number of notches 264a provided in each auxiliary electrode 264 may be appropriately selected, for example, from the range of 10 to 100. Alternatively, although not shown, each auxiliary electrode 264 may have one or multiple slits, similar to the radio wave reflecting element 120 of the first embodiment. The length, width, aspect ratio, and number of the slits may also be appropriately selected from the ranges described above.

[0076] The first alignment film 266 and the second alignment film 270 are both provided to cover the microstrip line 260 and the auxiliary electrode 264 and sandwich the liquid crystal layer 268. The alignment directions of the first alignment film 266 and the second alignment film 270 can be set arbitrarily and may be parallel or perpendicular to the longitudinal direction of the notch 264a (or slit), or may be tilted at any angle from the longitudinal direction. The alignment directions of the first alignment film 266 and the second alignment film 270 may be the same or different. For example, the alignment directions of the first alignment film 266 and the second alignment film 270 may be orthogonal to each other. The configurations of the first alignment film 266, the second alignment film 270, and the liquid crystal layer 268 can be similar to those of the first alignment film 168, the second alignment film 172, and the liquid crystal layer 170 of the radio wave reflecting element 120 of the first embodiment, respectively, and therefore further description thereof will be omitted.

[0077] The counter electrode 272 is provided on the liquid crystal layer 268 via a second alignment film 270. The counter electrode 272 can be provided as a single electrode integrated across multiple phase shifters 220 so that it can be shared by multiple phase shifters 220. Therefore, the counter electrode 272 is also referred to as a common electrode. A constant common potential is supplied to the counter electrode 272 directly from an external circuit (not shown) or via the drive circuit 206. A vertical electric field is generated in the liquid crystal layer 268 due to a potential difference between the counter electrode 272 and the microstrip line 260 and / or between the counter electrode 272 and the auxiliary electrode 264. This vertical electric field changes the orientation of the liquid crystal molecules, thereby controlling the dielectric constant of the liquid crystal layer 268. Since the phase shifter 220 may or may not transmit visible light, the counter electrode 272, like the microstrip line 260 and the auxiliary electrode 264, may also include the above-mentioned metals or alloys, or conductive oxides such as ITO and IZO.

[0078] The distance D between the microstrip line 260 and the auxiliary electrode 264 ３ (the distance from the upper surface of the microstrip line 260 to the lower surface of the auxiliary electrode 264) is the distance D between the auxiliary electrode 264 and the counter electrode 272 ４ The phase shifter 220 is configured so that the distance D is smaller than the distance from the upper surface of the auxiliary electrode 264 to the lower surface of the counter electrode 272 (see FIG. 18).３ is determined mainly by the second interlayer insulating film 262 and is, for example, 50 nm or more and 5 μm or less. ４ is mainly determined by the liquid crystal layer 268, the first alignment film 266, and the second alignment film 270, and is approximately the sum of the thickness of the liquid crystal layer 268 (for example, 20 μm to 50 μm, or 30 μm to 50 μm) and the thicknesses of the first alignment film 266 and the second alignment film 270. For example, the distance D ４ is the distance D ３ It may be set within the range of 200 times or more and 500 times or less.

[0079] The counter substrate 204 can have a similar structure to the substrate 202. The substrate 102 and the counter substrate 104 are sealed together by a sealant 212 (FIG. 14), and the liquid crystal layer 268 is sealed in a space created by the sealant 212, the substrate 202, and the counter substrate 204. As shown in FIGS. 16 to 18 , an undercoat 230 may be provided on the surface of the counter substrate 204 facing the liquid crystal layer 268 to prevent impurities in the counter substrate 204 from diffusing toward the liquid crystal layer 268. The undercoat 230 can also have a structure similar to that of the undercoat 222.

[0080] 2. Driving Method of Phased Array Antenna A driving method of the phased array antenna 200 will be described below with reference to Figures 19 to 21. Figure 19 is an example of a timing chart for driving the phased array antenna 200, which schematically shows the potential changes applied to the counter electrode 272, microstrip line 260, and auxiliary electrode 264 for one antenna 210 over seven consecutive frames. Figures 20 and 21 are schematic end views of the liquid crystal layer 268 and the antenna electrodes 280 of multiple antennas 210.

[0081] According to the timing chart of Figure 19, the phase shifter 220 is in the off state in the first, fourth, and seventh frames. In contrast, the phase shifter 220 is in the on state in the second and fifth frames, and an electric field is formed in the liquid crystal layer 268. As a result, the transmission direction of the radio wave is controlled in the second and fifth frames. In the example shown here, the electric field strength formed in the liquid crystal layer 268 in the second and fifth frames is different from that in the fifth frame, with the latter being stronger than the former. The third and sixth frames are also called overdrive periods, and as will be described later, providing these frames enables high-speed switching of the transmission direction of the radio wave.

[0082] (1) Off State In the first frame, the same potential (e.g., 0 V ground potential) is supplied to the microstrip line 260, the auxiliary electrode 264, and the counter electrode 272 in all antennas 210. In this state, these components are at the same potential, and no electric field is generated in the liquid crystal layer 268. Therefore, although not shown, similar to the liquid crystal layer 170 of the radio wave reflecting element 120 of the first embodiment, the liquid crystal molecules in the liquid crystal layer 268 are homogeneously aligned according to the alignment directions of the first alignment film 266 and the second alignment film 270. As a result, the dielectric constant of the liquid crystal layer 170 is the same for all antennas 210. The phase of the AC signal transmitted from the transmission wiring 208 to the microstrip line 260 varies depending on the dielectric constant of the liquid crystal layer 268. In the off state, the dielectric constant of the liquid crystal layer 170 is the same for all of the phase shifters 220, and therefore the spread (phase) of the radio waves transmitted from above and below the antenna electrode 280 is the same, as represented by the dotted arcs in Figure 20, which is a schematic end view of the multiple antennas 210. Therefore, the radio waves are transmitted in the front direction of the phased array antenna 200 (the side where the antenna electrode 280 is arranged) so as to be directed in the normal direction of the antenna electrode 280 (see the arrow in Figure 20).

[0083] (2) ON state: In the second frame following the first frame, the phase shifter 220 is turned ON. Specifically, the potential V ０is maintained at 0 V, in each phase shifter 220, the first transistor 240 is turned on while the second transistor 250 is kept off, and in this state, the potential V of the counter electrode 272 is transmitted from the signal line 216 to the microstrip line 260. ０ , and supplies an arbitrary potential (here, a potential of +aV) different from the potential V of the microstrip line 260. ｍ becomes +aV.

[0084] Then, the first transistor 240 is turned off. As a result, the potential V ｍ Next, while the first transistor 240 is kept in the off state, the second transistor 250 is turned on, and in this state, the potential V ０ , and supplies an arbitrary potential (here, a potential of +aV) different from the potential V of the auxiliary electrode 264. ａ In the above explanation, the potential V of the microstrip line 260 ｍ After setting the potential V of the auxiliary electrode 264 ａ However, the order of these is arbitrary. ｍ and the potential V of the auxiliary electrode 264 ａ may be the same or different from each other, but it is preferable that the potentials of these electrodes are the same so that a potential difference between the microstrip line 260 and the auxiliary electrode 264 does not generate a transverse electric field.

[0085] By the above operation, a potential difference is generated between the microstrip line 260 and the counter electrode 272, and between the auxiliary electrode 264 and the counter electrode 272. As a result, although not shown, a vertical electric field is generated in the liquid crystal layer 268, similar to the liquid crystal layer 170 of the radio wave reflecting element 120 of the first embodiment (see the dotted arrow in FIG. 8). The potential V ｍ and the potential V of the auxiliary electrode 264 ａis determined by the direction of transmission of the radio wave. As described above, the phase of the AC signal transmitted through the microstrip line 260 varies depending on the dielectric constant of the liquid crystal layer 268, and the greater the change in the dielectric constant, the greater the phase change. Furthermore, the change in the dielectric constant depends on the strength of the electric field generated in the liquid crystal layer 268. For this reason, when the phase of the AC signal is to be changed significantly, the potential V of the counter electrode 272 ｏ This can be achieved by applying a potential that is significantly different from the above to the microstrip line 260 and the auxiliary electrode 264 .

[0086] As with the radio wave reflecting element 120 of the first embodiment, when a longitudinal electric field is generated, the liquid crystal molecules rise, and as a result, the dielectric constant of the liquid crystal layer 268 changes due to the dielectric anisotropy of the liquid crystal molecules. Therefore, by changing the strength of the longitudinal electric field for each phase shifter 220, the phase of the AC signal can be changed for each antenna 210. As a result, as shown by the dotted semicircles in Figure 21, the phase of the radio wave transmitted from the antenna electrode 280 can be changed for each antenna 210, and the equiphase surface can be tilted, that is, the direction of the radio wave transmitted toward the antenna electrode 280 can be changed (see the open arrow in Figure 21).

[0087] Thereafter, when the phase shifter 220 is returned to the off state, in the third frame, the potential V ｏ to 0 V, and the potential V of the microstrip line 260 ｍ While maintaining the potential V of the auxiliary electrode 264 at +aV, ａ is returned to the initial potential of 0 V. This causes a potential difference between the microstrip line 260 and the auxiliary electrode 264, and as a result, a transverse electric field is generated between the microstrip line 260 and the auxiliary electrode 264, similar to the liquid crystal layer 170 of the radio wave reflecting element 120 (see FIG. 9). On the other hand, a potential difference still exists between the microstrip line 260 and the counter electrode 272, but as described above, the distance D ４ Compared to the distance D ３is so large that the vertical electric field can be ignored compared to this horizontal electric field. As a result, in the third frame, the liquid crystal molecules that stood up in the second frame can be forcibly returned to their original homogeneous orientation by utilizing the horizontal electric field. The contribution of the driving force due to this horizontal electric field allows the dielectric constant of the liquid crystal layer 268 to quickly return to its original dielectric constant. Thereafter, in the fourth frame, the potential V of the microstrip line 260 ｍ is returned to the initial potential (0 V), the state transitions to the OFF state.

[0088] Thereafter, when transitioning to an ON state in which the dielectric constant is changed even more significantly (fifth frame), a larger potential (a potential of +bV in the example of FIG. 19 , where b>a) can be applied to the microstrip line 260 and the auxiliary electrode 264, respectively. The same applies when transitioning to an OFF state again thereafter; in the sixth frame following the fifth frame, no potential difference is applied between the auxiliary electrode 264 and the counter electrode 272, but a potential difference is applied between the auxiliary electrode 264 and the microstrip line 260, thereby forming a transverse electric field. This allows the alignment state of the liquid crystal layer 268 to be quickly returned to a homogeneous alignment.

[0089] In the phase shifter 220, similarly to the radio wave reflecting element 120, inversion driving may be adopted to prevent burn-in of the liquid crystal layer 268. That is, between successive frames in the ON state, the potential V ｍ and V ａ The polarity of the potential V of the counter electrode 174 ｏ It may be inverted with respect to

[0090] As described above, similarly to the radio wave reflecting device 100, in the antenna 210 according to one embodiment of the present invention and the phased array antenna 200 including the antenna 210, the transverse electric field between the auxiliary electrode 264 and the microstrip line 260 can be utilized together with the van der Waals force to return the liquid crystal molecules, which have been raised by the longitudinal electric field, to a homogeneous orientation, as well. This allows the homogeneous orientation to be quickly reproduced, and as a result, it becomes possible to switch the radio wave transmission direction of the phased array antenna 200 at high speed. Therefore, by applying one of the embodiments of the present invention, it is possible to provide a phased array antenna that can change the radio wave transmission direction at high speed.

[0091] The above-described embodiments of the present invention can be combined as appropriate as long as they are not mutually contradictory. Furthermore, based on the radio wave reflecting element or radio wave reflecting device of each embodiment, a person skilled in the art can add or delete components or change the design as appropriate, or add or omit processes or change conditions, and these will also be included in the scope of the present invention as long as they include the gist of the present invention.

[0092] Even if there are other effects and advantages different from those brought about by the aspects of each of the above-mentioned 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.

[0093] 100: radio wave reflecting device, 102: substrate, 104: opposing substrate, 106: scanning line driving circuit, 108: signal line driving circuit, 110: terminal, 112: sealing material, 116: gate line, 116-1: first gate line, 116-2: second gate line, 118: signal line, 118-1: first signal line, 118-2: second signal line, 120: radio wave reflecting element, 122: undercoat, 124: gate insulating film, 126: first interlayer insulating film, 128: planarizing film , 130: undercoat, 140: first transistor, 142: gate electrode, 144: semiconductor film, 146: terminal, 148: terminal, 150: second transistor, 152: gate electrode, 154: semiconductor film, 156: terminal, 158: terminal, 160: liquid crystal element, 162: patch electrode, 164: second interlayer insulating film, 166: auxiliary electrode, 166a: slit, 166b: notch, 168: first alignment film, 170: liquid crystal layer, 172: No. 2 alignment film, 174: opposing electrode, 200: phased array antenna, 202: substrate, 204: opposing substrate, 206: driving circuit, 208: transmission wiring, 210: antenna, 212: sealing material, 214: gate line, 214-1: first gate line, 214-2: second gate line, 216: signal line, 220: phase shifter, 222: undercoat, 224: gate insulating film, 226: first interlayer insulating film, 228: planarizing film, 230: undercoat , 240: first transistor, 242: gate electrode, 244: semiconductor film, 246: terminal, 248: terminal, 250: second transistor, 252: gate electrode, 254: semiconductor film, 256: terminal, 258: terminal, 260: microstrip line, 262: second interlayer insulating film, 264: auxiliary electrode, 264a: notch, 266: first alignment film, 268: liquid crystal layer, 270: second alignment film, 272: counter electrode, 280: antenna electrode

Claims

1. A radio wave reflecting element comprising: a patch electrode; an insulating film on the patch electrode; an auxiliary electrode located on the insulating film and having at least one slit or notch overlapping with the patch electrode; a liquid crystal layer on the auxiliary electrode; and a counter electrode on the liquid crystal layer, wherein the patch electrode and the auxiliary electrode are configured to have variable potentials applied to them individually.

2. The radio wave reflecting element according to claim 1, wherein the distance between the auxiliary electrode and the counter electrode is greater than the distance between the auxiliary electrode and the patch electrode.

3. The radio wave reflecting element according to claim 1, wherein the opposing electrode is configured so that a constant potential is applied to it.

4. The radio wave reflecting element according to claim 1, further comprising a first transistor and a second transistor electrically connected to said patch electrode and said auxiliary electrode, respectively.

5. The radio wave reflecting element according to claim 1, further comprising: a first alignment film between the auxiliary electrode and the liquid crystal layer; and a second alignment film between the liquid crystal layer and the counter electrode.

6. A radio wave reflecting device comprising a plurality of radio wave reflecting elements arranged in a matrix shape having a plurality of rows and a plurality of columns, each of the plurality of radio wave reflecting elements comprising: a patch electrode; an insulating film on the patch electrode; an auxiliary electrode located on the insulating film and having at least one slit or notch overlapping with the patch electrode; a liquid crystal layer on the auxiliary electrode; and a counter electrode located on the liquid crystal layer and shared by the plurality of radio wave reflecting elements, the patch electrode and the auxiliary electrode being configured to be individually supplied with a variable potential.

7. The radio wave reflecting device according to claim 6, wherein the distance between said auxiliary electrode and said counter electrode is greater than the distance between said auxiliary electrode and said patch electrode.

8. The radio wave reflecting device according to claim 6, wherein the opposing electrode is configured so that a constant potential is applied to it.

9. The radio wave reflecting device according to claim 6, wherein each of the plurality of radio wave reflecting elements further comprises a first transistor and a second transistor electrically connected to the patch electrode and the auxiliary electrode, respectively.

10. The radio wave reflecting device according to claim 6, wherein each of the plurality of radio wave reflecting elements further comprises: a first alignment film between the auxiliary electrode and the liquid crystal layer; and a second alignment film between the liquid crystal layer and the opposing electrode.

11. A radio wave reflecting device as described in claim 9, further comprising a first gate line and a second gate line extending in the row direction, and a signal line intersecting the first gate line and the second gate line, wherein the first gate line is electrically connected to the first transistor of a first radio wave reflecting element selected from the plurality of radio wave reflecting elements, the second gate line is electrically connected to the second transistor of the first radio wave reflecting element, and the signal line is electrically connected to the first transistor and the second transistor of the first radio wave reflecting element.

12. The radio wave reflecting device of claim 11, wherein the signal line is selected from the plurality of radio wave reflecting elements and electrically connected to the first transistor and the second transistor of a second radio wave reflecting element located in the same row as the first radio wave reflecting element.

13. A radio wave reflecting device as described in claim 9, further comprising a gate line extending in a row direction, and a first signal line and a second signal line intersecting the gate line, wherein the gate line is electrically connected to a first transistor and a second transistor of a first radio wave reflecting element selected from the plurality of radio wave reflecting elements, the first signal line is electrically connected to the first transistor of the first radio wave reflecting element, and the second signal line is electrically connected to the second transistor of the first radio wave reflecting element.

14. The radio wave reflecting device of claim 13, wherein the gate line is selected from the plurality of radio wave reflecting elements and is electrically connected to the first transistor and the second transistor of a second radio wave reflecting element located in the same row as the first radio wave reflecting element.

15. An antenna comprising an antenna electrode and a phase shifter, the phase shifter having a microstrip line present in the same layer as the antenna electrode, an insulating film on the microstrip line, an auxiliary electrode located on the insulating film and having at least one slit or notch overlapping with the microstrip line, a liquid crystal layer on the auxiliary electrode, and a counter electrode on the liquid crystal layer, the antenna electrode being electrically insulated from the microstrip line via the insulating film.

16. The antenna according to claim 15, wherein the distance between the auxiliary electrode and the counter electrode is greater than the distance between the auxiliary electrode and the microstrip line.

17. The antenna according to claim 15, further comprising a transmission wiring that is present in the same layer as said microstrip line and is electrically insulated from said microstrip line via said insulating film.

18. The antenna according to claim 15, wherein the microstrip line and the auxiliary electrode are configured to have variable potentials applied thereto individually, and the counter electrode is configured to have a constant potential applied thereto.

19. The antenna of claim 15, further comprising a first transistor and a second transistor electrically connected to said microstrip line and said auxiliary electrode, respectively.

20. The antenna of claim 15, further comprising: a first alignment film between the auxiliary electrode and the liquid crystal layer; and a second alignment film between the liquid crystal layer and the counter electrode.

Images