Radio wave reflecting elements and radio wave reflectors

Abstract

This radio wave reflection element comprises a first electrode, a first alignment film, a second alignment film, a liquid crystal layer, a third alignment film, a fourth alignment film, and a second electrode. The first alignment film is positioned above the first electrode. The second alignment film is positioned above the first alignment film, and is in contact with the first alignment film. The liquid crystal layer is positioned above the first alignment film and the second alignment film, and includes liquid crystal molecules. The third alignment film is positioned above the liquid crystal layer. The fourth alignment film is positioned above the liquid crystal layer and the third alignment film, and is in contact with the liquid crystal layer and the third alignment film. The second electrode is positioned above the fourth alignment film. In a first region overlapping with the first electrode, the first alignment film and the fourth alignment film are respectively exposed from the second alignment film and the third alignment film.

Description

Technical Field

[0001] One embodiment of the present invention relates to a radio wave reflecting element and a radio wave reflecting plate including the radio wave reflecting element.

Background Art

[0002] Since liquid crystal molecules have dielectric anisotropy, the dielectric constant of a 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. For example, Patent Documents 1 and 2 disclose a metasurface whose characteristics can be controlled by adjusting the electric field applied to the liquid crystal layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] One of the problems of one embodiment of the present invention is to provide a radio wave reflecting plate including a radio wave reflecting element having a new structure. Alternatively, one of the problems of one embodiment of the present invention is to provide a radio wave reflecting plate including a radio wave reflecting element capable of switching the reflection direction at high speed.

Means for Solving the Problems

[0005] One embodiment of the present invention is a radio wave reflecting element. This radio wave reflecting element comprises a first electrode, a first alignment film, a second alignment film, a liquid crystal layer, a third alignment film, a fourth alignment film, and a second electrode. The first alignment film is located on the first electrode. The second alignment film is located on the first alignment film and is in contact with the first alignment film. The liquid crystal layer is located on the first and second alignment films and contains liquid crystal molecules. The third alignment film is located on the liquid crystal layer. The fourth alignment film is located on the liquid crystal layer and the third alignment film and is in contact with the liquid crystal layer and the third alignment film. The second electrode is located on the fourth alignment film. In a first region overlapping with the first electrode, the first and fourth alignment films are exposed from the second and third alignment films, respectively.

[0006] One embodiment of the present invention is a radio wave reflector. This radio wave reflector comprises a plurality of radio wave reflecting elements arranged in a matrix. Each of the plurality of radio wave reflecting elements comprises a first electrode, a first alignment layer, a second alignment layer, a liquid crystal layer, a third alignment layer, a fourth alignment layer, and a second electrode. The first alignment layer is located on the first electrode. The second alignment layer is located on the first alignment layer and is in contact with the first alignment layer. The liquid crystal layer is located on the first and second alignment layers and contains liquid crystal molecules. The third alignment layer is located on the liquid crystal layer. The fourth alignment layer is located on the liquid crystal layer and the third alignment layer and is in contact with the liquid crystal layer and the third alignment layer. The second electrode is located on the fourth alignment layer. In a first region overlapping with the first electrode, the first and fourth alignment layers are exposed from the second and third alignment layers, respectively. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic top view of a radio wave reflector according to one embodiment of the present invention. [Figure 2] A schematic top view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 3] A schematic end view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 4A] A schematic end view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 4B]A schematic end view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 5A] A schematic end view showing a method for manufacturing a radio wave reflecting element according to one embodiment of the present invention. [Figure 5B] A schematic end view showing a method for manufacturing a radio wave reflecting element according to one embodiment of the present invention. [Figure 6A] A schematic diagram showing the characteristics of a radio wave reflector according to one embodiment of the present invention. [Figure 6B] A schematic diagram showing the characteristics of a radio wave reflector according to one embodiment of the present invention. [Figure 7A] A schematic top view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 7B] A schematic top view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 7C] A schematic top view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 7D] A schematic top view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 8] A schematic top view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 9A] A schematic end view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 9B] A schematic end view of a radio wave reflecting element according to one embodiment of the present invention. [Figure 10] A schematic top view of a radio wave reflector according to one embodiment of the present invention. [Figure 11] An example of an equivalent circuit of a radio wave reflecting element according to one embodiment of the present invention. [Figure 12] A schematic end view of a radio wave reflecting element according to one embodiment of the present invention. [Modes for carrying out the invention]

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

[0009] For the sake of clearer explanation, the drawings may schematically represent the width, thickness, shape, etc. of each part compared with the actual embodiment, but this is merely an example and does not limit the interpretation of the present invention. In this specification and each figure, elements having the same functions as those described with respect to the previously presented figures may be denoted by the same reference numerals, and redundant descriptions may be omitted.

[0010] In this specification and the claims, when expressing the aspect of arranging one structure on another structure, if simply expressed as "on", unless otherwise specified, it includes both the case of arranging another structure directly on a certain structure so as to be in contact with it and the case of arranging another structure above a certain structure through yet another structure.

[0011] In this specification and the claims, the expression "a certain structure is exposed from another structure" means an aspect where a part of a certain structure is not covered by another structure, and the part not covered by this other structure also includes the aspect of being covered by yet another structure.

[0012] (First Embodiment) In this embodiment, a radio wave reflector 100, which is one of the embodiments of the present invention, will be described. The radio wave reflector 100 has a function of reflecting the irradiated radio waves in an arbitrary direction. The frequency of the wavelength that can be reflected is in the range of 400 MHz to 50 GHz, typically radio waves in the band of 400 MHz to 6.0 GHz, radio waves in the band of 2.5 GHz to 4.7 GHz, radio waves in the band of 24 GHz to 50 GHz, etc.

[0013] 1. Overall Structure Figure 1 shows a schematic top view of the radio wave reflector 100. The radio wave reflector 100 has a substrate 102 and a counter substrate 104 (not shown in Figure 1), and a plurality of radio wave reflecting elements 120 arranged in a matrix between the substrate 102 and the counter substrate 104. In the example shown in Figure 1, 13 radio wave reflecting elements 120 are arranged in the row direction (x direction in the figure), and 14 radio wave reflecting elements 120 are arranged in the column direction (y direction perpendicular to the x direction in the figure). There is no restriction on the number of radio wave reflecting elements 120, and they can be determined arbitrarily. The number of rows and columns are also arbitrary and may be the same or different from each other. The surface formed by the arrangement of the plurality of radio wave reflecting elements 120, that is, a single surface (reflection surface) that simultaneously encloses all radio wave reflecting elements 120, may be a square, a rectangle, or a circle. Preferably, the reflection surface has one or more axes of symmetry passing through the reflection surface.

[0014] The substrate 102 and the opposing substrate 104 are fixed to each other by a sealing material 106 containing a resin such as epoxy resin or acrylic resin. A liquid crystal layer 140, described later, is sealed in the space formed by the substrate 102, the opposing substrate 104, and the sealing material 106. A drive circuit 110 for generating a potential (control potential) to control the radio wave reflecting elements 120 is provided on the substrate 102, and wiring 112 for supplying the control potential to the first electrode 122 (described later) of the radio wave reflecting elements 120 is connected to the drive circuit 110 and the multiple radio wave reflecting elements 120. The drive circuit 110 may be formed from a metal film, insulating film, or semiconductor film provided on the substrate 102, or it may be an IC chip having an integrated circuit provided on a semiconductor substrate.

[0015] 1-1. Circuit board Figure 2 shows a schematic top view of one radio wave reflector 120, and Figure 3 shows a schematic end view along the dashed line AA' in Figure 1. In Figure 3, one radio wave reflector 120-1 is shown along with a portion of the radio wave reflector 120-2 adjacent to it and the sealing material 106.

[0016] The substrate 102 and the opposing substrate 104 are provided to give physical strength to the radio wave reflector 100 and to provide a surface for arranging the radio wave reflecting element 120 and the drive circuit 110 for driving it. The substrate 102 and / or the opposing substrate 104 may be flexible. The substrate 102 and the opposing substrate 104 may include inorganic insulators such as glass and quartz, semiconductors such as silicon, polymers such as polyimide, polycarbonate and polyester, and metals such as aluminum, copper and stainless steel. If conductive materials such as metals are included, it is preferable to provide a film containing an insulator such as silicon oxide or silicon nitride on the surface on which the radio wave reflecting element 120 is provided, i.e., the surface of the substrate 102 on the side of the opposing substrate 104 and the surface of the opposing substrate 104 on the side of the substrate 102. At least one of the substrate 102 and the opposing substrate 104 is configured to transmit at least a portion of ultraviolet light or a portion of visible light. For example, the substrate 102 and / or the opposing substrate 104 are configured to transmit at least a portion of light in the wavelength range of 300 nm to 800 nm, preferably light in the wavelength range of 300 nm to 400 nm.

[0017] 1-2. Radio wave reflecting elements As shown in Figures 2 and 3, each radio wave reflecting element 120 basically comprises a first electrode (also called a patch electrode) 122, a second electrode 124, a first alignment layer 130, a second alignment layer 132, a third alignment layer 134, a fourth alignment layer 136, and a liquid crystal layer 140, all sandwiched between the substrate 102 and the opposing substrate 104. For ease of viewing, only the first electrode 122, the second alignment layer 132, and the second electrode 124 are shown in Figure 2.

[0018] (1) First electrode The first electrode 122 is provided on the substrate 102. Optionally, the first electrode 122 may be formed on the substrate 102 via an undercoat 128 composed of one or more films containing an inorganic compound such as silicon oxide or silicon nitride. As shown in Figure 2, in the radio wave reflector 100, the first electrodes 122 of adjacent radio wave reflecting elements 120 in the column or row direction are electrically connected and conduct to each other. Therefore, for example, the first electrodes 122 of multiple radio wave reflecting elements 120 arranged in one column are conduction to each other and at the same potential, but in this case, these first electrodes 122 do not conduct to the first electrodes 122 of radio wave reflecting elements 120 arranged in other columns. Similarly, if the first electrodes 122 of multiple radio wave reflecting elements 120 arranged in one row are conduction to each other and at the same potential, these first electrodes 122 do not conduct to the first electrodes 122 of radio wave reflecting elements 120 arranged in other rows.

[0019] The first electrode 122 may be made of a metal such as copper, aluminum, tungsten, molybdenum, or titanium, an alloy containing at least one of these metals, or a conductive oxide such as indium-tin oxide (ITO) or indium-zinc oxide (IZO). The first electrode 122 may have a single-layer structure or a laminated structure in which layers of different compositions are stacked. The first electrode 122 may be formed by applying methods such as sputtering or chemical vapor deposition (CVD).

[0020] Here, the first electrode 122 does not occupy the entire surface occupied by one radio wave reflecting element 120 on the substrate 102, but only a portion of it. Therefore, in the examples shown in Figures 2 and 3, the first electrode 122 occupies a portion of the surface occupied by each radio wave reflecting element 120, including the center, while the second alignment film 132 and the third alignment film 134, which will be described later, are arranged in the other areas.

[0021] (2) First alignment film The first alignment film 130 is provided to control the orientation of the liquid crystal molecules constituting the liquid crystal layer 140 provided thereon. The first alignment film 130 is placed on the first electrode 122 and covers the first electrode 122. The first alignment film 130 is provided continuously across a plurality of radio wave reflecting elements 120. In other words, it is not separated between adjacent radio wave reflecting elements 120, but is shared by all radio wave reflecting elements 120. The first alignment film 130 contains a polymer such as polyimide or polyester. The first alignment film 130 is formed using a wet film deposition method such as inkjet, spin coating, printing, or dip coating, and its surface is rubbed.

[0022] (3) Second alignment layer A second alignment film 132 is also provided to control the orientation of liquid crystal molecules. The second alignment film 132 contains a polymer having a different composition from the first alignment film 130. Specifically, the second alignment film 132 contains a linear or crosslinked polymer having liquid crystalline side chains. There are no restrictions on the structure of such polymers. For example, the basic skeleton of the polymer constituting the second alignment film 132 can be poly(meth)acrylate, polyoxyethylene, polyester, polysilane, polyamide, polyurethane, or polysiloxane. The side chains include rigid substituents (mesogens) and further include spacers that link the rigid substituents to the main chain. The side chains may further include terminal groups that are attached to the rigid substituents without being bonded to the main chain. Examples of rigid substituents include aromatic substituents in which multiple aromatic rings such as biphenyl groups are directly bonded, aromatic imino groups, azobenzene groups, aromatic ester groups, stilbene groups, diarylacetylenes, etc. Examples of spacers include alkyl groups, alkoxy groups, and ester groups. Examples of terminal groups include alkyl groups, alkoxy groups, alkyl ester groups, and cyano groups. The method for preparing the second orientation film 132 will be described later.

[0023] The second alignment film 132 is provided so as not to overlap with the first electrode 122. That is, in a direction perpendicular to the upper surface of the substrate 102, the second alignment film 132 does not overlap with the first electrode 122, or does not substantially overlap with it. Therefore, in the region that overlaps with the first electrode, the first alignment film 130 is exposed from the second alignment film 132 and is in direct contact with the liquid crystal layer 140. On the other hand, in regions other than the above region, the second alignment film 132 is in direct contact with the liquid crystal layer 140 and is sandwiched between the first alignment film 130 and the liquid crystal layer 140. In other words, the second alignment film 132 has multiple openings, each opening overlapping with the first electrode 122. The second alignment film 132 may be continuous across adjacent radio wave reflecting elements 120 (Figure 3). That is, the second alignment film 132 may be shared by multiple radio wave reflecting elements 120.

[0024] The second alignment film 132 is configured such that the long axes of the liquid crystal molecules overlapping with the second alignment film 132 are tilted from the upper surface of the substrate 102, and the angle of this tilt (tilt angle) is greater than that of the region in direct contact with the first alignment film 130 (i.e., the region overlapping with the first electrode 122).

[0025] (4) Liquid crystal layer The liquid crystal layer 140 contains liquid crystal molecules. The structure of the liquid crystal molecules is not limited. Therefore, the liquid crystal molecules may be nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, or chiral smectic liquid crystals.

[0026] The liquid crystal layer 140 is in direct contact with the second alignment film 132 and in direct contact with the first alignment film 130 in the region overlapping with the first electrode 122. The thickness of the liquid crystal layer 140 is, for example, 20 μm to 100 μm, or 30 μm to 50 μm. Therefore, the height of the sealing material 106 is also selected from this range. Although not shown in the figures, a spacer may be provided within the liquid crystal layer 140 to maintain this thickness throughout the entire radio wave reflector 100. However, if the above-described thickness of the liquid crystal layer 140 is adopted in a liquid crystal display device, it will be impossible to obtain the high responsiveness necessary for displaying moving images, making it extremely difficult to perform the function of a liquid crystal display device.

[0027] (5) Third alignment layer Similar to the second alignment film 132, the third alignment film 134 is also provided to control the orientation of liquid crystal molecules and has the same composition and structure as the second alignment film 132. The third alignment film 134 overlaps with the second alignment film 132 but does not overlap with the first electrode 122, or does not substantially overlap with it. In other words, the third alignment film 134 is in direct contact with the liquid crystal layer 140 in regions other than the region that overlaps with the first electrode 122. Similar to the second alignment film 132, the third alignment film 134 also has an opening that overlaps with the first electrode 122. Therefore, the second alignment film 132 and the third alignment film 134 have openings that overlap each other. The shapes of the openings of the second alignment film 132 and the third alignment film 134 may be the same or different. The third alignment film 134 may also be continuous across adjacent radio wave reflecting elements 120 (Figure 3). In other words, the third alignment film 134 may also be shared by multiple radio wave reflecting elements 120.

[0028] As described above, the third alignment film 134 has the same structure as the second alignment film 132, and therefore its contribution to the tilt of the liquid crystal molecules is also the same. Consequently, the tilt angle of the liquid crystal molecules located on the third alignment film 134, that is, the liquid crystal molecules overlapping with the third alignment film 134, is greater than that of the regions directly in contact with the first alignment film 130 and the fourth alignment film (i.e., the regions overlapping with the first electrode 122).

[0029] (6) Fourth alignment layer The fourth alignment film 136 has the same function as the first alignment film 130, aligning liquid crystal molecules. The fourth alignment film 136 has the same composition and structure as the first alignment film 130, and the rubbing direction is also the same. The fourth alignment film 136 overlaps with the first electrode 122 and the second electrode 124 and is continuously provided across multiple radio wave reflecting elements 120. Furthermore, in the region where the fourth alignment film 136 overlaps with the first electrode 122, it does not overlap with the second alignment film 132 or the fourth alignment film 136. In other words, in the region overlapping with the first electrode, the fourth alignment film 136 is exposed from the third alignment film 134 and is in direct contact with the liquid crystal layer 140. On the other hand, the third alignment film 134 is in direct contact with the liquid crystal layer 140 in regions other than this region and is sandwiched between the fourth alignment film 136 and the liquid crystal layer 140.

[0030] (7) Second electrode The second electrode 124 is provided on the opposing substrate 104 (below the opposing substrate 104 in Figure 3). Alternatively, the second electrode 124 may be formed on the substrate 102 via an overcoat 138 composed of one or more films containing inorganic compounds such as silicon oxide or silicon nitride. In the examples shown in Figures 2 and 3, the second electrode 124 is provided across all radio wave reflecting elements 120. That is, the second electrode 124 is shared by all radio wave reflecting elements 120. A constant potential is supplied to the second electrode 124 from an external circuit via wiring (not shown).

[0031] Similar to the first electrode 122, the second electrode 124 may also contain metals such as copper, aluminum, tungsten, molybdenum, or titanium, alloys containing at least one of these metals, or conductive oxides such as indium-tin oxide (ITO) or indium-zinc oxide (IZO). The second electrode 124 may also have a single-layer structure or a laminated structure in which layers of different compositions are stacked. The second electrode 124 may also be formed by applying methods such as sputtering or chemical vapor deposition (CVD).

[0032] 2. Method for manufacturing a radio wave reflector The method for manufacturing the radio wave reflector 100 will be explained using the end views shown in Figures 4A and 4B. These figures show three consecutive radio wave reflecting elements 120. Similar to known liquid crystal display devices, a first electrode 122 and a first alignment film 130 are sequentially formed on the substrate 102. Meanwhile, a second electrode 124 and a fourth alignment film 136 are formed on the opposing substrate 104. The first alignment film 130 and the fourth alignment film 136 are subjected to a rubbing process.

[0033] Subsequently, the substrate 102 and the opposing substrate 104 are positioned such that the rubbing directions of the first alignment film 130 and the fourth alignment film 136 are the same, and the first alignment film 130 and the fourth alignment film 136 are sandwiched between the substrate 102 and the opposing substrate 104, and the substrate 102 and the opposing substrate 104 are bonded together using the sealing material 106. Then, the liquid crystal layer 140 is injected into the space surrounded by the substrate 102, the opposing substrate 104, and the sealing material 106. Alternatively, an uncured or partially cured sealing material 106 may be placed on either the substrate 102 or the opposing substrate 104, and the liquid crystal layer 140 may be dropped into the area surrounded by the sealing material 106. Then, the other substrate 102 or opposing substrate 104 may be placed on the sealing material 106, and the sealing material 106 may be cured.

[0034] At this time, as shown in Figure 4A, the liquid crystal layer 140 contains a reactive mesogen (indicated by a circle in the figure) and a photoinitiator (not shown). The reactive mesogen is a molecule that has both polymerizable substituents and rigid substituents within the same molecule via a spacer, and polymerizes to give a linear or crosslinked polymer with rigid substituents in its side chains. The reactive mesogen may also be an oligomer. The photoinitiator is a molecule that absorbs ultraviolet or visible light to generate a cationic species or radical, and known photoinitiators can be used.

[0035] With the substrate 102 sandwiching the liquid crystal layer 140 and the opposing substrate 104 bonded together, light is irradiated from the side of the first electrode 122 (see arrow in Figure 4A). The irradiated light (irradiated light) includes light of a wavelength absorbed by the photoinitiator. If the first electrode 122 does not transmit the irradiated light, the irradiated light is partially shielded by the first electrode 122, and the irradiated light is selectively absorbed by the photoinitiator in the region where the first electrode 122 is not provided, and polymerization and / or crosslinking of the reactive mesogen proceeds. As a result, in the region where the first electrode 122 is not provided, the second alignment film 132 and the third alignment film 134 are selectively formed on the first alignment film 130 and the fourth alignment film 136, respectively (see Figure 3).

[0036] If the first electrode 122 transmits the irradiation light, the light irradiation may be performed via a photomask 114 having a light-transmitting portion 114b and a light-shielding portion 114a (Figure 4B). The photomask 114 is configured such that the light-transmitting portion 114b overlaps with the first electrode 122, and the light-shielding portion 114a does not overlap with the first electrode 122. If the second electrode 124 transmits the irradiation light, the light irradiation may be performed from the second electrode 124 side via the photomask 114.

[0037] As described above, the first alignment film 130 and the fourth alignment film 136 are subjected to a rubbing treatment. As a result, the rigid substituents of the reactive mesogen contained in the liquid crystal layer 140 before polymerization or crosslinking are oriented in a certain direction between the first alignment film 130 and the fourth alignment film 136, and polymerization or crosslinking can proceed by light irradiation while maintaining this state. Therefore, near the interface between the second alignment film 132 and the liquid crystal layer 140, and near the interface between the third alignment film 134 and the liquid crystal layer 140, the polymer formed by crosslinking the reactive mesogen can fix the liquid crystal molecules at a large tilt angle (pre-tilt angle). Consequently, the second alignment film 132 and the third alignment film 134 have a higher ability to tilt liquid crystal molecules compared to the first alignment film 130 and the fourth alignment film 136. As a result, in the region sandwiched between the second alignment film 132 and the third alignment film 134, the pretilt angle of the liquid crystal molecules in the absence of an electric field is larger compared to the other regions. Hereinafter, the region of the liquid crystal layer 140 sandwiched between the second alignment film 132 and the third alignment film 134 will be called the high pretilt region, and the region not sandwiched between the second alignment film 132 and the third alignment film 134, and in direct contact with the first alignment film 130 and the second alignment film 132 (i.e., the region occupied by the first electrode 122 within the radio wave reflecting element 120, and the region overlapping with the first electrode 122) will be called the low pretilt region. In the embodiment of the present invention, by selectively polymerizing or crosslinking reactive mesogens within each radio wave reflecting element 120, high pretilt regions and low pretilt regions can be created separately within each radio wave reflecting element 120.

[0038] 3.Operation The operation of the radio wave reflector 100 will be explained using the schematic end views shown in Figures 5A and 5B. These figures show three consecutive radio wave reflecting elements 120.

[0039] As described above, each radio wave reflector 120 has a high pretilt region and a low pretilt region. In the low pretilt region, the rubbing direction of the first alignment film 130 and the fourth alignment film 136 are the same, so in the absence of an electric field, the liquid crystal molecules tend to adopt a spray orientation. On the other hand, by appropriately changing the control potential to apply a potential difference between the first electrode 122 and the second electrode 124, an electric field is generated in the liquid crystal layer 140, causing the liquid crystal molecules to rotate and transition from spray orientation to bend orientation. Therefore, by appropriately adjusting the control potential, the dielectric constant of the liquid crystal layer 140 in each radio wave reflector 120 can be greatly changed.

[0040] Normally, the transition from spray orientation to bend orientation is slow, resulting in a longer response time (time required for dielectric constant change). However, each radio wave reflector 120 has a high pre-tilt region. In the high pre-tilt region, due to the contribution of the second alignment film 132 and the third alignment film 134, the liquid crystal molecules tilt significantly even in the absence of an electric field, allowing them to adopt a strongly bent orientation. That is, the average tilt angle is large. Furthermore, since the first electrode 122 does not exist in the high pre-tilt region, no electric field is generated in this high pre-tilt region even if a potential difference is applied between the first electrode 122 and the second electrode 124. Therefore, this bend orientation does not depend on the magnitude of the electric field. In other words, a strong bend orientation exists stably in the high pre-tilt region.

[0041] As a result, the low-pretilt region is influenced by the orientation of the adjacent high-pretilt region, and as shown in Figure 5A, it can have a relatively high tilt angle even in the absence of an electric field. Specifically, in the absence of an electric field, the average tilt angle of the liquid crystal molecules in the low-pretilt region is smaller than that of the high-pretilt region, but larger than when the high-pretilt region is absent. In other words, in the low-pretilt region, the liquid crystal molecules can adopt a pseudo-bent orientation even in the absence of an electric field. When an electric field is applied to the liquid crystal layer 140 in this state, the liquid crystal molecules in the low-pretilt region that have adopted a pseudo-bent orientation can respond quickly and transition to a bent orientation (Figure 5B). Therefore, a large response speed can be obtained.

[0042] Therefore, the radio wave reflector 100 equipped with the radio wave reflecting element 120 having the above configuration can function as a radio wave reflector capable of switching the direction of radio wave reflection. For example, consider a situation where radio waves (wavy lines in the figure) are irradiated onto the radio wave reflector 100 as shown in Figure 6A. At this time, a constant potential is applied to the second electrode 124. On the other hand, the first electrode 122 is given individual control potentials for each column or row from the drive circuit 110. As a result, the tilt angle of the liquid crystal molecules contained in the liquid crystal layer 140 changes for each column or row, and consequently, the dielectric constant of the liquid crystal layer 140 changes for each column or row. When the dielectric constant changes, the amount of phase shift of the reflected wave changes, so the phase shift of the reflected wave from the radio wave reflector 100 also shifts for each column or row. As a result, the direction of propagation of the radio waves changes. That is, it becomes possible to reflect radio waves at a reflection angle different from the incident angle of the radio waves. For example, in the examples shown in Figures 6A and 6B, the incident angle of the radio waves is 0°, but the reflection angle is greater than 0°.

[0043] The amount of phase change can be changed by appropriately controlling the control potential applied to the first electrode 122, and therefore the reflection angle can be arbitrarily controlled. Specifically, when the first electrodes 122 of adjacent radio wave reflecting elements 120 in the column direction (y direction in Figure 1) are at the same potential, the reflection axis A extending in the column direction yThe radio wave reflector 100 can function as a uniaxial radio wave reflector having the following characteristics: Conversely, if the first electrode 122 of adjacent radio wave reflecting elements 120 in the row direction (x direction in Figure 1) is at the same potential, the reflection axis A extending in the row direction can be used. x The radio wave reflector 100 can function as a single-axis radio wave reflector having the following properties.

[0044] As described above, in the radio wave reflector 100 according to the embodiment of the present invention, each radio wave reflecting element 120 is provided with a high pretilt region and a low pretilt region. Although the high pretilt region does not contribute to dielectric constant control of the liquid crystal layer 140, it can be used to artificially bend the liquid crystal layer 140 in the low pretilt region, which contributes to dielectric constant control, in the absence of an electric field. Therefore, the liquid crystal layer in the low pretilt region can be bent and oriented with a large response speed. With this mechanism, the radio wave reflector 100 can function as a radio wave reflector with a large response speed.

[0045] 4. Variations There are no restrictions on the planar shape of the first electrode 122 (shape on the closed surface of the substrate 102). It may have a shape without an opening, as shown in Figure 2, or it may have one or more openings (or slits), as shown in Figures 7A and 7B. In other words, in each radio wave reflecting element 120, the first electrode 122 may have a ring shape. The shape of the opening may be a polygon including a square or rectangle, and the outline of the opening may be composed of a curve. Specifically, the opening may be a circle (Figure 7C) or an ellipse (Figure 7D). Preferably, the first electrode 122 is aligned with the axis of symmetry A parallel to the reflection axis of the radio wave reflector 100. s It holds.

[0046] The shape of the second electrode 124 is also arbitrary; it may have no opening and be a continuous shape across the entire reflective surface (see Figures 1 and 3).

[0047] Alternatively, as shown in Figure 8, a schematic top view of the four radio wave reflecting elements 120, and the schematic end face views along the dashed lines BB' and CC' in Figure 8 (Figures 9A and 9B), if the first electrode 122 has an opening (see Figures 7A to 7D), the second electrode 124 may have an opening that overlaps with at least a portion of the opening of the first electrode 122. The opening of the second electrode 124 may overlap with the entire opening of the first electrode 122. Similar to the first electrode 122, the shape of the opening of the second electrode 124 can be arbitrarily set and may be a polygon including a square or rectangle, or part or all of the contour may be composed of curves, such as a circle or ellipse. The shape of the opening of the second electrode 124 may be the same as or different from the opening of the first electrode 122. The second alignment film 132 and the third alignment film 134 are arranged so as not to overlap with the first electrode 122 and the second electrode 124.

[0048] In the modified example described above, each radio wave reflecting element 120 has a high pretilt region that overlaps with the second alignment film 132 and the third alignment film 134, as well as a low pretilt region that does not overlap with the second alignment film 132 and the third alignment film 134 but overlaps with the first electrode 122. Therefore, the liquid crystal in the low pretilt region can adopt a pseudo-bent orientation due to the high pretilt region. As a result, the liquid crystal layer 140 in the low pretilt region responds quickly to the electric field and transitions to a bent orientation, creating a large change in dielectric anisotropy in each radio wave reflecting element 120.

[0049] (Second Embodiment) In this embodiment, a radio wave reflector 150, which has a different structure from the radio wave reflector 100 described in the first embodiment, will be described. Configurations that are the same as or similar to those described in the first embodiment may be omitted from the description.

[0050] Figure 10 shows a schematic top view of the radio wave reflector 150, and Figure 11 shows an example of the equivalent circuit of each radio wave reflecting element 120. One difference between the radio wave reflector 150 and the radio wave reflector 150 is that in the radio wave reflector 150, the first electrodes 122 of the multiple radio wave reflecting elements 120 are controlled independently without conducting to each other. Specifically, two drive circuits (gate line drive circuit 152 and signal line drive circuit 154) that control the multiple radio wave reflecting elements 120 are provided on the substrate 102. Multiple gate wires 156 extend in the row direction from the gate line drive circuit 152, and the gate line drive circuit 152 supplies gate signals to the multiple radio wave reflecting elements 120 connected to each gate wire 156. On the other hand, the signal line drive circuit 154 is connected to multiple signal lines 158 that extend in the column direction via wiring 112, and supplies control potential to the multiple radio wave reflecting elements 120 connected to each signal line 158. The gate line drive circuit 152 and the signal line drive circuit 154 may be formed from a metal film, insulating film, or semiconductor film provided on the substrate 102, or they may be formed by placing an IC chip having an integrated circuit provided on a semiconductor substrate on the substrate 102. Furthermore, there are no restrictions on the number of gate line drive circuits 152; for example, a pair of gate line drive circuits 152 may be provided so as to sandwich a reflective surface.

[0051] As shown in the example of the equivalent circuit in Figure 11, each radio wave reflecting element 120 has at least one transistor 160, with a gate wire 156 connected to its gate electrode and a signal line 158 connected to one terminal (the first terminal). The other terminal (the second terminal) of the transistor 160 is connected to a first electrode 122 for controlling the liquid crystal layer 140. In an optional configuration, each radio wave reflecting element 120 may have a capacitive element 180 between the gate wire and the second terminal of the transistor. Although not shown, the radio wave reflecting element 120 may also have further transistors and capacitive elements.

[0052] Figure 12 shows a schematic end face diagram of one radio wave reflector 120. The transistor 160 is provided directly on the substrate 102 or via an undercoat 128. The transistor 160 illustrated in Figure 12 is a so-called bottom-gate transistor and has a gate electrode 162, a gate insulating film 164 on the gate electrode 162, a semiconductor film 166 on the gate insulating film 164, and a first terminal 168 and a second terminal 170 on the semiconductor film 166. There are no restrictions on the configuration of the transistor 160; it may be a top-gate transistor, or a dual-gate transistor having gate electrodes 162 above and below the semiconductor film 166. There are also no restrictions on the upper limit relationships between the first terminal 168 and the semiconductor film 166, and between the second terminal 170 and the semiconductor film 166. The semiconductor film 166 may contain group 14 elements such as silicon, or it may be an oxide semiconductor such as indium gallium oxide or indium gallium zinc oxide.

[0053] A first interlayer insulating film 172, composed of one or more films containing silicon oxide or silicon nitride, is provided at the first terminal 168 and the second terminal 170. A conductive connecting pad 174 is electrically connected to the second terminal 170 through an opening in the first interlayer insulating film 172. A planarization film 178 is provided on the connecting pad 174, either directly or via the second interlayer insulating film 176, to absorb irregularities caused by the transistor 160 and other components and provide a flat top surface. The planarization film 178 and the second interlayer insulating film 176 have openings that expose the connecting pad 174, and a first electrode 122 formed on the planarization film 178 is electrically connected to the connecting pad 174 through these openings. In an optional configuration, a third interlayer insulating film 182 may be formed between the planarization film 178 and the first electrode 122.

[0054] In the radio wave reflector 150, the second electrode 124 is provided across multiple radio wave reflecting elements 120, and a constant potential is supplied. Meanwhile, the gate signal supplied to the gate wiring 156 operates the transistor 160, and when the transistor 160 is ON, a control potential is supplied from the signal line 158 to the first electrode 122 via the transistor 160. As a result, an electric field based on the potential difference between the control potential and the constant potential applied to the second electrode 124 is applied to the liquid crystal layer 140. Therefore, by sequentially selecting the radio wave reflecting elements 120 row by row using multiple gate wirings 156 and sequentially supplying the control potential to the selected radio wave reflecting elements 120 from multiple signal lines, it is possible to supply arbitrarily set control potentials to each of the multiple radio wave reflecting elements 120 independently. In other words, the dielectric constant of the liquid crystal layer 140 can be individually controlled in each of the multiple radio wave reflecting elements 120. Therefore, unlike the radio wave reflector 100, the radio wave reflector 150 has two reflective axes A extending in the column direction and the column direction (y direction and x direction in Figure 10, respectively). y , A x It can function as a two-axis radio wave reflector having [a specific feature / ability].

[0055] In the radio wave reflector 150, the radio wave reflecting elements 120 described in the first embodiment are also provided, and each radio wave reflecting element 120 is provided with a high pretilt region and a low pretilt region. As a result, the liquid crystal layer 140 in the low pretilt region, which contributes to dielectric constant control, can be pseudo-bent in the absence of an electric field, and the liquid crystal layer 140 in the low pretilt region can be bent and oriented with a large response speed. With this mechanism, the radio wave reflector 150 can function as a radio wave reflector with a large response speed.

[0056] The embodiments described above as examples of the present invention can be combined and implemented as appropriate, insofar as they do not contradict each other. Furthermore, any additions, deletions, or design modifications of components, or additions, omissions, or changes to processes based on the radio wave reflecting elements or radio wave reflectors of each embodiment, made by those skilled in the art, are also included within the scope of the present invention, as long as they retain the essence of the present invention.

[0057] Any effects or benefits other than those brought about by the embodiments described above, if they are clear from the description herein or easily predictable to a person skilled in the art, are naturally considered to be brought about by the present invention. [Explanation of Symbols]

[0058] 100: Radio wave reflector, 102: Substrate, 104: Opposing substrate, 106: Encapsulation material, 110: Drive circuit, 112: Wiring, 114: Photomask, 114a: Light-shielding part, 114b: Light-transmitting part, 120: Radio wave reflecting element, 120-1: Radio wave reflecting element, 120-2: Radio wave reflecting element, 122: First electrode, 124: Second electrode, 128: Undercoat, 130: First alignment film, 132: Second alignment film, 134: Third alignment film, 136: Fourth alignment 138: Overcoat, 140: Liquid crystal layer, 150: Radio wave reflector, 152: Gate line drive circuit, 154: Signal line drive circuit, 156: Gate wiring, 158: Signal line, 160: Transistor, 162: Gate electrode, 164: Gate insulating film, 166: Semiconductor film, 168: First terminal, 170: Second terminal, 172: First interlayer insulating film, 174: Connection pad, 176: Second interlayer insulating film, 178: Planarization film, 180: Capacitive element

Claims

1. First electrode, The first alignment film on the first electrode, A second orientation film located on the first orientation film and in contact with the first orientation film, A liquid crystal layer containing liquid crystal molecules is located on the first alignment film and the second alignment film. The third alignment film on the liquid crystal layer, A fourth alignment film located on the liquid crystal layer and the third alignment film, and in contact with the liquid crystal layer and the third alignment film, and The fourth orientation film comprises a second electrode, In a first region overlapping with the first electrode, the first alignment film and the fourth alignment film are exposed from the second alignment film and the third alignment film, respectively, in a radio wave reflecting element.

2. The first alignment film and the fourth alignment film are in direct contact with the liquid crystal layer in the first region. The second alignment film is sandwiched between the first alignment film and the liquid crystal layer in regions other than the first region. The radio wave reflecting element according to claim 1, wherein the third alignment film is sandwiched between the fourth alignment film and the liquid crystal layer in regions other than the first region.

3. The radio wave reflecting element according to claim 1, wherein neither the second alignment film nor the third alignment film overlaps with the first electrode.

4. The radio wave reflecting element according to claim 1, wherein the second alignment film and the third alignment film are configured such that, when there is no potential difference between the first electrode and the second electrode, the tilt angle of the liquid crystal molecules in regions other than the first region is greater than the tilt angle in the first region.

5. The radio wave reflecting element according to claim 1, wherein each of the second alignment film and the third alignment film has a first opening that overlaps with each other.

6. The first electrode has a first opening, The radio wave reflecting element according to claim 1, wherein the second alignment film and the third alignment film overlap with the first aperture.

7. The radio wave reflecting element according to claim 6, wherein the second electrode overlaps with the first aperture.

8. The radio wave reflecting element according to claim 6, wherein the second electrode has a second aperture that overlaps with the first aperture.

9. The radio wave reflecting element according to claim 8, wherein the first aperture and the second aperture have the same shape.

10. It is equipped with multiple radio wave reflecting elements arranged in a matrix, Each of the aforementioned plurality of radio wave reflecting elements is First electrode, The first alignment film on the first electrode, A second orientation film located on the first orientation film and in contact with the first orientation film, A liquid crystal layer containing liquid crystal molecules is located on the first alignment film and the second alignment film. The third alignment film on the liquid crystal layer, A fourth alignment film located on the liquid crystal layer and the third alignment film, and in contact with the liquid crystal layer and the third alignment film, and The fourth orientation film comprises a second electrode, A radio wave reflector in which, in a first region overlapping with the first electrode, the first alignment film and the fourth alignment film are exposed from the second alignment film and the third alignment film, respectively.

11. The radio wave reflector according to claim 10, wherein the first electrodes of two adjacent radio wave reflecting elements are electrically conductive to each other.

12. The radio wave reflector according to claim 10, wherein each of the plurality of radio wave reflecting elements further comprises a transistor electrically connected to the first electrode.

13. The first alignment film and the fourth alignment film are in direct contact with the liquid crystal layer in the first region. The second alignment film is sandwiched between the first alignment film and the liquid crystal layer in regions other than the first region. The radio wave reflector according to claim 10, wherein the third alignment film is sandwiched between the fourth alignment film and the liquid crystal layer in regions other than the first region.

14. The radio wave reflector according to claim 10, wherein neither the second alignment film nor the third alignment film overlaps with the first electrode.

15. The radio wave reflector according to claim 10, wherein the second alignment film and the third alignment film are configured such that, when there is no potential difference between the first electrode and the second electrode, the tilt angle of the liquid crystal molecules in regions other than the first region is greater than the tilt angle in the first region.

16. The radio wave reflector according to claim 10, wherein each of the second alignment film and the third alignment film has a first opening that overlaps with each other.

17. The first electrode has a first opening, The radio wave reflector according to claim 10, wherein the second alignment film and the third alignment film overlap with the first opening.

18. The radio wave reflector according to claim 16, wherein the second electrode overlaps with the first aperture.

19. The radio wave reflector according to claim 16, wherein the second electrode has a second opening that overlaps with the first opening.

20. The radio wave reflector according to claim 19, wherein the first opening and the second opening have the same shape.

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