Liquid crystal metasurface reflecting plate

Abstract

This liquid crystal metasurface reflection plate comprises: a plurality of patch electrodes that are arranged in a matrix; a control electrode that overlaps the patch electrodes; and a liquid crystal layer between the patch electrodes and the control electrode. The control electrode is divided into a plurality of sub-control electrodes, and the plurality of sub-control electrodes include first sub-control electrodes and second sub-control electrodes adjacent to the first sub-control electrodes. When a first control signal is input into the first sub-control electrodes and a second control signal is input into the second sub-control electrodes, the potential difference of the first sub-control electrodes with respect to the patch electrodes and the potential difference of the second sub-control electrodes with respect to the patch electrodes are equal in absolute value, and the directions of the electric fields are opposite.

Description

Liquid crystal metasurface reflector

[0001] One embodiment of the present invention relates to a metasurface reflector using liquid crystal that can control the reflection directionality of radio waves.

[0002] A radio wave reflector (also called a metasurface reflector; hereinafter referred to as a "liquid crystal metasurface reflector") has been disclosed that controls the reflection direction of radio waves by utilizing the dielectric anisotropy of liquid crystals (see, for example, Patent Document 1). The liquid crystal metasurface reflector has a patch electrode arranged on the radio wave incident surface, a ground electrode arranged on the opposite side, and a liquid crystal layer provided between the patch electrode and the ground electrode.

[0003] Japanese Patent Application Laid-Open No. 2022-156917

[0004] The multiple batch electrodes arranged on the liquid crystal metasurface reflector are connected by strip wiring. It is considered preferable that the width of the strip wiring is wide in order to reduce resistance loss. However, increasing the width of the strip wiring affects the reflection characteristics.

[0005] A liquid crystal metasurface reflector according to one embodiment of the present invention includes a plurality of patch electrodes arranged in a matrix, a control electrode overlapping the patch electrode, and a liquid crystal layer between the patch electrode and the control electrode. The control electrode is divided into a plurality of sub-control electrodes, each of which includes a first sub-control electrode and a second sub-control electrode adjacent to the first sub-control electrode. When a first control signal is input to the first sub-control electrode and a second control signal is input to the second sub-control electrode, the potential difference between the first sub-control electrode and the patch electrode and the potential difference between the second sub-control electrode and the patch electrode are equal in absolute value and have opposite electric field directions.

[0006] 1 is a diagram illustrating the configuration of a liquid crystal metasurface reflector according to one embodiment of the present invention; FIG. 2 is a plan view of batch electrodes and control electrodes provided in a liquid crystal metasurface reflector according to one embodiment of the present invention; FIG. 3 is a cross-sectional view of batch electrodes and control electrodes provided in a liquid crystal metasurface reflector according to one embodiment of the present invention; FIG. 4 is a diagram illustrating the operation of a liquid crystal metasurface reflector according to one embodiment of the present invention; FIG. 5 is a diagram illustrating the configuration of a liquid crystal metasurface reflector according to one embodiment of the present invention; FIG. 6 is a plan view of batch electrodes and control electrodes provided in a liquid crystal metasurface reflector according to one embodiment of the present invention;

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different forms, and should not be construed as being limited to the description of the following exemplary embodiments. For clarity of explanation, the drawings may show schematic representations of the width, thickness, shape, etc. of each part compared to the actual form. However, these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those previously described with reference to the preceding drawings are designated by the same reference numerals (or reference numerals with A, B, etc. suffixed thereto), and detailed descriptions may be omitted as appropriate. Furthermore, the letters "first" and "second" attached to each element are convenient labels used to distinguish each element and have no further meaning unless otherwise specified.

[0008] In this specification, when a component or region is referred to as being "on (or under)" another component or region, unless otherwise specified, this includes not only the case where it is directly above (or directly under) the other component or region, but also the case where it is above (or under) the other component or region, i.e., the case where another component is included between the component or region and above (or under) the other component or region.

[0009] FIG. 1 shows a plan view of a liquid crystal metasurface reflector 100 according to one embodiment of the present invention, viewed from the radio wave incident surface side.

[0010] For the sake of explanation, Fig. 1 indicates the X-axis direction, the Y-axis direction, and the Z-axis direction as indicated by the arrows in the figure. In the figure, the Y-axis direction is perpendicular to the X-axis direction, and the Z-axis direction is perpendicular to the XY plane. The X-axis direction and the Y-axis direction can be read as the first direction and the second direction. The relationship between the three directions, the X-axis direction, the Y-axis direction, and the Z-axis direction, is the same in other figures referred to in this embodiment, unless otherwise specified.

[0011] The liquid crystal metasurface reflector 100 includes a plurality of patch electrodes 102 and a plurality of control electrodes 104. The plurality of patch electrodes 102 are arranged in the X-axis direction and the Y-axis direction. Similarly, the plurality of control electrodes 104 are arranged so as to overlap with the plurality of patch electrodes 102. The plurality of patch electrodes 102 are arranged on the incident surface of the radio wave, and the plurality of control electrodes 104 are arranged on the back surface of the plurality of patch electrodes 102.

[0012] Although not shown in FIG. 1 , a liquid crystal layer is provided between the plurality of patch electrodes 102 and the plurality of control electrodes 104. The liquid crystal layer is made of a liquid crystal material having dielectric anisotropy. The liquid crystal material may have either positive or negative dielectric anisotropy. There are no particular limitations on the type of liquid crystal material, provided that it has dielectric anisotropy. For example, nematic liquid crystal is used as the liquid crystal material.

[0013] The liquid crystal metasurface reflector 100 has a structure in which a first substrate 150 and a second substrate 152 are stacked on top of each other. The first substrate 150 and the second substrate 152 are insulating substrates. A liquid crystal layer (not shown) is sandwiched between the first substrate 150 and the second substrate 152. The first substrate 150 is disposed on the radio wave incident surface side (front surface), and the second substrate 152 is disposed on the rear surface side of the first substrate 150.

[0014] A plurality of patch electrodes 102 are arranged on a first substrate 150. The plurality of patch electrodes 102 are arranged with gaps between them so that adjacent electrodes do not contact each other. A plurality of control electrodes 104 are arranged on a second substrate 152. The plurality of control electrodes 104 are also arranged with gaps between them so that adjacent electrodes do not contact each other.

[0015] On the second substrate 152, the ground electrode 108 is arranged so as to fill the gaps in the area where the plurality of control electrodes 104 are arranged. The plurality of control electrodes 104 and the ground electrode 108 are arranged so as to be continuous in a plan view, but are arranged on different layers so as not to be in direct contact in a cross-sectional view. For example, a structure is provided in which an insulating layer is interposed between the plurality of control electrodes 104 and the ground electrode 108.

[0016] The patch electrodes 102 have individually separated patterns and are in an electrically floating state. The control electrodes 104 are used as electrodes for controlling the orientation of liquid crystal molecules in the liquid crystal layer. Predetermined control signals are applied to the control electrodes 104. Details of the predetermined control signals will be described later.

[0017] The control electrode 104 is composed of a plurality of sub-control electrodes. Fig. 1 shows an example in which the control electrode 104 is composed of two sub-control electrodes, a first sub-control electrode 105A and a second sub-control electrode 105B. A control signal is applied to each of the first sub-control electrode 105A and the second sub-control electrode 105B individually.

[0018] A plurality of scanning signal lines 111 and a plurality of control signal lines 113 are arranged on the second substrate 152. The plurality of scanning signal lines 111 and the plurality of control signal lines 113 are arranged according to the arrangement of the plurality of control electrodes 104. The plurality of scanning signal lines 111 extend in the X-axis direction, and the plurality of control signal lines 113 extend in the Y-axis direction. The second substrate 152 may further be provided with a scanning signal line driving circuit 110, a control signal line selection circuit 112, and a terminal unit 114. The scanning signal line driving circuit 110 outputs scanning signals to the plurality of scanning signal lines 111, and the control signal line selection circuit 112 has the function of selecting the plurality of control signal lines 113. The terminal unit 114 is a portion where signals and power that drive the liquid crystal metasurface reflector 100 are input, and is a contact point with an external circuit. The terminal unit 114 is composed of a plurality of terminal electrodes 115.

[0019] The multiple scanning signal lines 111, the multiple control signal lines 113, the scanning signal line driving circuit 110, and the control signal line selection circuit 112 are elements for driving the multiple control electrodes 104 (first sub-control electrodes 105A, second sub-control electrodes 105B). Although not shown in FIG. 1 , switching elements are provided corresponding to the first sub-control electrodes 105A and the second sub-control electrodes 105B. The switching elements are selected (on / off controlled) by the scanning signal lines 111, and control signals are input from the control signal lines 113. Since the multiple control signal lines 113 are arranged corresponding to the arrangement of the first sub-control electrodes 105A and the second sub-control electrodes 105B, individual control signals are applied to the first sub-control electrodes 105A and the second sub-control electrodes 105B, respectively. That is, a first control signal is applied to the first sub-control electrode 105A, and a second control signal is applied to the second sub-control electrode 105B.

[0020] The first control signal and the second control signal are voltage signals having the same absolute value but different polarities. For example, when the first control signal has a positive voltage level, the second control signal has a negative voltage level. The polarities of the first control signal and the second control signal can be reversed as appropriate.

[0021] The ground electrode 108 is disposed so as to fill the gaps between the control electrodes 104, and is controlled so as to maintain a constant potential. The constant potential is, for example, ground.

[0022] FIG. 2 shows a plan view of a pair of patch electrodes 102 and control electrodes 104 provided on the liquid crystal metasurface reflector 100. Similar to FIG. 1, FIG. 2 shows an example in which the control electrode 104 is composed of a first sub-control electrode 105A and a second sub-control electrode 105B. The first sub-control electrode 105A and the second sub-control electrode 105B are arranged side by side at a predetermined interval. The first sub-control electrode 105A and the second sub-control electrode 105B are arranged so as to overlap with the patch electrode 102 in a planar view. The areas of the first sub-control electrode 105A and the second sub-control electrode 105B are the same. In other words, the area where the first sub-control electrode 105A overlaps with the patch electrode 102 is equal to the area where the second sub-control electrode 105B overlaps with the patch electrode 102.

[0023] The first sub-control electrode 105A is connected to the first switching element 116A, and the second sub-control electrode 105B is connected to the second switching element 116B. The first switching element 116A and the second switching element 116B are formed, for example, by thin film transistors. When the first switching element 116A and the second switching element 116B are formed by thin film transistors, they have three terminals: a gate terminal, a signal input terminal, and a signal output terminal. The gate terminals of the first switching element 116A and the second switching element 116B are connected to the first scanning signal line 111A. The signal input terminal of the first switching element 116A is connected to the first control signal line 113A, and the signal input terminal of the second switching element 116B is connected to the second control signal line 113B. The signal output terminal of the first switching element 116A is connected to the first sub-control electrode 105A, and the signal output terminal of the second switching element 116B is connected to the second sub-control electrode 105B.

[0024] 1 , the first scanning signal line 111A extends in the X-axis direction, and the first control signal line 113A and the second control signal line 113B extend in the Y-axis direction. The first control signal line 113A and the second control signal line 113B are arranged below the ground electrode 108. Therefore, when viewed from the patch electrode 102, the first control signal line 113A and the second control signal line 113B are shielded by the ground electrode 108. The ground electrode 108 has an opening in a region overlapping with the control electrode 104, and therefore, it is preferable that the first control signal line 113A and the second control signal line 113B are arranged so as not to overlap with the first sub-control electrode 105A and the second sub-control electrode 105B in this opening region. Note that the layout of the patch electrode 102 and the control electrode 104 shown in FIG. 2 is an example and is not limited to this structure.

[0025] FIG. 3 shows a cross-sectional view corresponding to the line A-B shown in FIG. 2. As shown in FIG. 3, a patch electrode 102 is provided on a first substrate 150, and a control electrode 104 (first sub-control electrode 105A, second sub-control electrode 105B) is provided on a second substrate 152. The first substrate 150 and the second substrate 152 are arranged so that the patch electrode 102 and the control electrode 104 (first sub-control electrode 105A, second sub-control electrode 105B) face each other, and are spaced apart with a predetermined gap between them. The gap between the first substrate 150 and the second substrate 152 is approximately 20 μm to 100 μm, for example, 40 μm. Although not shown, a spacer may be provided between the first substrate 150 and the second substrate 152 to maintain a constant gap.

[0026] A first alignment film 107A is provided on the first substrate 150 so as to cover the patch electrode 102, and a second alignment film 107B is provided on the second substrate 152 so as to cover the control electrode 104 (first sub-control electrode 105A, second sub-control electrode 105B). A liquid crystal layer 106 is provided so as to be sandwiched between the first substrate 150 and the second substrate 152. The initial alignment state of the liquid crystal layer 106 is regulated by the first alignment film 107A and the second alignment film 107B.

[0027] The second substrate 152 is provided with a first switching element 116A connected to the first sub-control electrode 105A and a second switching element 116B connected to the second sub-control electrode 105B. As described above, the first switching element 116A and the second switching element 116B are formed, for example, by thin film transistors. The first switching element 116A and the second switching element 116B are covered with an insulating layer 109. The first sub-control electrode 105A and the second sub-control electrode 105B may be provided on the insulating layer 109. The first sub-control electrode 105A and the first switching element 116A, and the second sub-control electrode 105B and the second switching element 116B are connected by contact holes formed in the insulating layer 109.

[0028] As described above, the first switching element 116A and the second switching element 116B have three terminals: a gate terminal, a signal input terminal, and a signal output terminal. Fig. 3 shows a structure in which the signal input terminal of the first switching element 116A is connected to the first control signal line 113A, the signal output terminal is connected to the first sub-control electrode 105A, and the signal input terminal of the second switching element 116B is connected to the second control signal line 113B, and the signal output terminal is connected to the second sub-control electrode 105B.

[0029] Although not shown in detail in Fig. 3 , the insulating layer 109 has a structure in which a plurality of insulating films are stacked. The first control signal line 113A and the second control signal line 113B are provided in the insulating layer 109 so as to be located in a layer below the first sub-control electrode 105A and the second sub-control electrode 105B. Although not shown in Fig. 3 , the scanning signal line 111 is also provided in the insulating layer 109. The scanning signal line 111, the first control signal line 113A, and the second control signal line 113B are provided in different layers in the insulating layer 109. The scanning signal line 111, the first control signal line 113A, and the second control signal line 113B intersect with each other, with an insulating layer interposed at the intersection.

[0030] A ground electrode 108 is provided on the second substrate 152. The ground electrode 108 is provided so as to fill the region where the first sub-control electrode 105A and the second sub-control electrode 105B are separated from each other. As shown in Fig. 3, an insulating layer 109 is interposed between the ground electrode 108 and the first sub-control electrode 105A and the second sub-control electrode 105B to prevent direct contact between the two.

[0031] Although the ground electrode 108 and the control electrode 104 (first sub-control electrode 105A, second sub-control electrode 105B) are physically separated, a single ground plane is formed for radio waves (high-frequency radio waves) incident on the liquid crystal metasurface reflector 100. Therefore, it is preferable that the ends of the ground electrode 108 are arranged so as to overlap with the first sub-control electrode 105A and the second sub-control electrode 105B.

[0032] 3 shows an example in which the ground electrode 108 is formed in a layer different from the layer in which the switching elements 116 (first switching element 116A, second switching element 116B) are formed, but the configuration of the ground electrode 108 is not limited to this example. The ground electrode 108 may be formed, for example, in the same conductive layer as the layer in which the control signal line 113 is formed, or, although not shown, may be formed in the same conductive layer as the layer in which the scanning signal line is formed. Note that the layered structure shown in FIG. 3 is just an example, and the layered structure of each signal line and each electrode is not limited to the structure shown in the figure.

[0033] The first substrate 150 and the second substrate 152 are formed of flat materials such as glass, resin, or metal plate. The layers provided on the first substrate 150 and the second substrate 152 are formed using the following materials. The semiconductor layer forming the switching element 116 (thin-film transistor) is formed of a silicon semiconductor such as amorphous silicon or polycrystalline silicon, or an oxide semiconductor including a metal oxide such as indium oxide, zinc oxide, or gallium oxide. The insulating layer 109 may be formed of any insulating material, such as an inorganic insulating material such as a silicon oxide film or a silicon nitride film, or an organic insulating material such as acrylic, epoxy, or polyimide. Wiring such as the scanning signal line 111 and the control signal line 113, and electrodes such as the control electrode 104, the ground electrode 108, and the patch electrode 102 are formed of conductive materials, such as metal materials such as aluminum (Al), titanium (Ti), molybdenum (Mo), molybdenum-tungsten (MoW), and copper (Cu).

[0034] 4A and 4B are diagrams explaining the operation of the liquid crystal metasurface reflector 100, showing the states of the control signals applied to the control electrodes 104 (first sub-control electrode 105A, second sub-control electrode 105B). Fig. 4A shows a plan view of the patch electrode 102 and the control electrode 104 (first sub-control electrode 105A, second sub-control electrode 105B), and Fig. 4B shows a cross-sectional view of the patch electrode 102 and the control electrode 104 (first sub-control electrode 105A, second sub-control electrode 105B).

[0035] 4A and 4B , the first sub-control electrode 105A and the second sub-control electrode 105B are arranged to overlap one patch electrode 102. Control signals are applied to the first sub-control electrode 105A and the second sub-control electrode 105B in pairs of high-level and low-level voltages. That is, when a high-level voltage (first control signal) is applied to the first sub-control electrode 105A as a control signal, a low-level voltage (second control signal) is applied to the second sub-control electrode 105B.

[0036] For example, when a high-level voltage of +30 V is applied to the first sub-control electrode 105A, a low-level voltage of 0 V is applied to the second sub-control electrode 105B. Control signals of this polarity generate electric fields E1 and E2 between the patch electrode 102 and the first and second sub-control electrodes 105A and 105B. The electric field E1 generated between the first sub-control electrode 105A and the patch electrode 102 and the electric field E2 generated between the second sub-control electrode 105B and the patch electrode 102 have opposite electric field directions but are the same in magnitude.

[0037] FIG. 4B schematically shows the liquid crystal molecules 118 contained in the liquid crystal layer 106. The liquid crystal molecules 118 have a long, rod-like structure. When subjected to the electric fields E1 and E2, the liquid crystal molecules 118 are oriented so that the longitudinal direction of the rod-like molecules is parallel to the direction of the electric field. The dielectric constant of the liquid crystal layer 106 changes depending on the orientation state of the liquid crystal molecules 118. When radio waves are reflected by the liquid crystal metasurface reflector 100, the phase of the reflected wave changes depending on the dielectric constant of the liquid crystal layer 106. The orientation direction of the liquid crystal molecules 118 present between the first sub-control electrode 105A and the patch electrode 102 is opposite to the orientation direction of the liquid crystal molecules 118 present between the second sub-control electrode 105B and the patch electrode 102, but the dielectric constant is the same.

[0038] The control signal may be a polarity-reversing signal that periodically reverses between positive and negative polarity. For example, in the first sub-control electrode 105A, a positive voltage may be applied in the first half cycle and a negative voltage may be applied in the second half cycle. The frequency of the control signal that reverses polarity within one cycle may be arbitrary. The control signal may have a frequency of, for example, 30 to 120 Hz, for example, 60 Hz. The polarity of the control signal applied to the second sub-control electrode 105B is reversed from that of the control signal applied to the first sub-control electrode 105A, i.e., a negative voltage is applied in the first half cycle and a positive voltage is applied in the second half cycle.

[0039] Because the liquid crystal layer 106 is a dielectric, the stacked structure of the first sub-control electrode 105A, the liquid crystal layer 106, and the patch electrode 102 can be considered a single capacitor. The same is true for the stacked structure of the second sub-control electrode 105B, the liquid crystal layer 106, and the patch electrode 102. When a high-level signal is applied as a control signal to the first sub-control electrode 105A and a low-level signal is applied to the second sub-control electrode 105B, the potential of the patch electrode 102 becomes intermediate between the high and low levels. As a result, an electric field E1 is generated from the first sub-control electrode 105A to the patch electrode 102, and an electric field E2 is generated from the patch electrode 102 to the second sub-control electrode 105B. Although the directions of the electric fields E1 and E2 are opposite to each other, their strengths are the same.

[0040] In the liquid crystal metasurface reflector 100, when the patch electrode 102 side is used as a common electrode, the patch electrodes must be connected with strip wiring to maintain a constant potential on the patch electrode side. While thinner strip wiring is considered preferable, excessively thin strip wiring can increase wiring resistance and cause delays in the input and output of electric charges. As a result, the potential difference between the patch electrode and the control electrode may not be as designed. On the other hand, thicker strip wiring can affect the reflective characteristics due to the strip wiring exposed on the reflective surface.

[0041] To address these concerns, the liquid crystal metasurface reflector 100 of this embodiment has a control electrode 104 divided into two, to which high-level and low-level control signals, or positive control signals and negative control voltages, are applied, and the patch electrode 102 is in a floating state, so that charge movement is completed within the same patch electrode 102, eliminating the need for external charge supply. As a result, the reflection characteristics within the surface of the metasurface reflector 100 can be made uniform even if the strip wiring is thinned or omitted.

[0042] The liquid crystal metasurface reflector 100 is designed to detect radio wave frequency bands including the very high frequency (VHF), ultra-high frequency (UHF), super high frequency (SHF), submillimeter wave (THF), extra high frequency (EHF), and terahertz wave bands. The orientation of the liquid crystal molecules 118 in the liquid crystal layer 106 changes in response to a control signal applied to the control electrode 104, but the orientation hardly changes with the frequency of the radio wave incident on the patch electrode 102. Therefore, the dielectric constant of the liquid crystal layer 106 can be changed by the control electrode 104, and the patch electrode 102 can reflect the radio wave, thereby controlling the phase of the reflected radio wave (the direction of travel of the reflected wave).

[0043] As described above, the liquid crystal metasurface reflector 100 according to this embodiment can drive the patch electrodes 102 in a floating state. However, as shown in FIG. 5 , the patch electrodes 102 may be connected by strip wiring 103. While FIG. 5 illustrates a structure in which patch electrodes 102 arranged in the Y-axis direction are connected by strip wiring 103, the connection direction of the strip wiring 103 is not limited to the illustrated example. The strip wiring 103 may be used to connect the patch electrodes 102 arranged along the X-axis direction, or may be used to connect in both the X-axis and Y-axis directions. Furthermore, as described above, in addition to connecting patch electrodes 102 to each other by strip wiring 103, each patch electrode 102 may be connected to a constant voltage source. The strip wiring 103 may have high resistance. This configuration allows static electricity entering the patch electrodes 102 to be removed via the strip wiring 103, which is expected to prevent electrostatic breakdown.

[0044] 5, the width of the strip wiring 103 connecting the patch electrodes 102 may be extremely thin. The width W2 of the strip wiring 103 may be 1 / 100 or less of the length W1 of one side of the patch electrode 102. For example, if the length W1 of one side of the patch electrode 102 is 10 mm, the line width of the strip wiring may be 100 μm or less.

[0045] The strip wiring 103 may have a linear shape in plan view, or may be bent in a crank shape as shown in Fig. 5. The length of the strip wiring 103 is set to a value equal to or greater than the effective wavelength λ of the reflected radio wave. ｇ Specifically, λ ｇ It is preferable that the effective wavelength is within ±10% of the relative dielectric constant ε of the liquid crystal layer. ｓ Based on this, λ is expressed as the following equation (1). ｇ = λ / (ε ｓ ) １／２ (1) By making the length of the strip wiring 103 approximately half the effective wavelength of the radio wave as described above, the current density distribution generated in the patch electrode 102 can be prevented from being disturbed, and reflection loss can be suppressed.

[0046] 2 shows an example in which the control electrode 104 is divided into two, a first sub-control electrode 105A and a second sub-control electrode 105B, but the control electrode 104 may be divided into more sub-control electrodes 105. For example, as shown in FIG. 6, the control electrode 104 may be divided into a total of 36 sub-control electrodes 105 by arranging six sub-control electrodes 105 in the X-axis direction and six sub-control electrodes 105 in the Y-axis direction.

[0047] As in the example described with reference to Figure 2, the 36 sub-control electrodes 105 shown in Figure 6 have the same area. In other words, the area over which each sub-control electrode 105 overlaps with the patch electrode 102 is the same. In this case, when a positive voltage (first control signal) is applied to the first sub-control electrode 105A, it is preferable that a negative voltage (second control signal) is applied to the second sub-control electrode 105B adjacent to it in the X-axis direction, and that a negative voltage (second control signal) is also applied to the third sub-control electrode 105C adjacent to it in the Y-axis direction. Furthermore, when a negative voltage (second control signal) is applied to the third sub-control electrode 105C, it is preferable that a positive voltage (first control signal) is applied to the fourth sub-control electrode 105D adjacent to it in the X-axis direction. In this way, when the control electrode 104 is divided into multiple sub-control electrodes 105 and a first control signal (positive voltage) and a second control signal (negative voltage) are applied, it is preferable that the sum of the positive and negative charges induced in the patch electrode 102 within one frame period be zero.

[0048] The polarity of the control signal as shown in Figure 6 can be individually controlled, as in the example shown in Figure 2, by connecting a switching element 116 to each sub-control electrode 105 and providing a control signal line according to the arrangement of each sub-control electrode.

[0049] According to the configuration of the liquid crystal metasurface reflector 100 of this embodiment, when a control signal is applied, charge migration is completed within one patch electrode 102, eliminating the need for an external charge supply. As a result, strip wiring connected to the patch electrode 102 is not required, or even if strip wiring is connected, the wiring width can be made extremely thin, thereby reducing the impact on reflection characteristics. Furthermore, since there is no need to supply charge to the patch electrode 102, the patch electrode 102 can be made floating, simplifying the structure.

[0050] The various configurations of the liquid crystal metasurface reflector exemplified as one embodiment of the present invention can be combined as appropriate as long as they are not mutually inconsistent. Furthermore, liquid crystal metasurface reflectors disclosed in this specification and drawings, to which a person skilled in the art has appropriately added, deleted, or modified components, or to which a process has been added, omitted, or conditions have been changed, are also included within the scope of the present invention as long as they contain the gist of the present invention.

[0051] Even if there are other effects and advantages different from those brought about by the aspects of the embodiments disclosed in this specification, 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.

[0052] 100: Liquid crystal metasurface reflector, 102: Patch electrode, 103: Strip wiring, 104: Control electrode, 105A: First sub-control electrode, 105B: Second sub-control electrode, 106: Liquid crystal layer, 107A: First alignment film, 107B: Second alignment film, 108: Ground electrode, 109: Insulating layer, 110: Scanning signal line drive circuit, 111: Scanning signal line, 112: Control signal line selection circuit, 113: Control signal line, 113A: First control signal line, 113B: Second control signal line, 114: Terminal section, 115: Terminal electrode, 116: Switching element, 116A: First switching element, 116B: Second switching element, 118: Liquid crystal molecules, 150: First substrate, 152: Second substrate

Claims

1. A liquid crystal metasurface reflector comprising: a plurality of patch electrodes arranged in a matrix; a control electrode overlapping the patch electrode; and a liquid crystal layer between the patch electrode and the control electrode, wherein the control electrode is divided into a plurality of sub-control electrodes, and the plurality of sub-control electrodes include a first sub-control electrode and a second sub-control electrode adjacent to the first sub-control electrode, wherein when a first control signal is input to the first sub-control electrode and a second control signal is input to the second sub-control electrode, the potential difference of the first sub-control electrode with respect to the patch electrode and the potential difference of the second sub-control electrode with respect to the patch electrode have the same absolute value and the electric field directions are opposite.

2. The liquid crystal metasurface reflector of claim 1, wherein the areas of the first sub-control electrode and the second sub-control electrode are equal.

3. A liquid crystal metasurface reflector as described in claim 1, wherein the overlapping area between the first sub-control electrode and the patch electrode is equal to the overlapping area between the second sub-control electrode and the patch electrode.

4. The liquid crystal metasurface reflector of claim 1, wherein the plurality of patch electrodes are individually arranged in isolation.

5. The liquid crystal metasurface reflector of claim 1, wherein the plurality of patch electrodes are connected by strip wiring.

6. The liquid crystal metasurface reflector of claim 5, wherein the width of the strip wiring is 1 / 100 or less of the length of one side of the patch electrode.

7. A liquid crystal metasurface reflector as described in claim 4 or 5, wherein the plurality of patch electrodes are in a floating state.

8. A liquid crystal metasurface reflector as described in claim 1, wherein the plurality of sub-control electrodes are arranged spaced apart and a ground electrode is provided so as to overlap the area where the plurality of sub-control electrodes are spaced apart.

9. The liquid crystal metasurface reflector of claim 1, wherein one of the first control signal and the second control signal is a high-level signal and the other is a low-level signal.

10. The liquid crystal metasurface reflector of claim 1, wherein the first control signal and the second control signal are signals with equal absolute values ​​and inverted positive and negative polarities, and the positive and negative polarities are periodically inverted.

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