US-20260128529-A1 - RADIO WAVE REFLECTING DEVICE

Abstract

A radio wave reflecting device includes a radio wave reflecting element and a solar cell. The radio wave reflecting element includes a first substrate provided with bias electrodes arranged in a matrix, a second substrate provided with a common electrode facing the first substrate and overlapping the bias electrode, and a liquid crystal layer between the first substrate and the second substrate. The solar cell includes a light guide having a first surface and a second surface opposite the first surface and a side surface between the first surface and the second surface and a light-receiving portion provided along the side surface. The second surface of the solar cell is arranged to face the first substrate of the radio wave reflecting element, and a light receiving surface of the light-receiving portion is arranged on a side of the light guiding portion.

Inventors

• Shinichiro Oka
• Mitsutaka Okita
• Koichi Igeta
• Hiroumi KINJO

Assignees

• JAPAN DISPLAY INC.

Dates

Publication Date

20260507

Application Date

20251230

Priority Date

20230713

Claims (11)

1. 1 . A radio wave reflecting device comprising: a radio wave reflecting element; and a solar cell, the radio wave reflecting element comprising: a first substrate provided with bias electrodes arranged in a matrix; a second substrate provided with a common electrode facing the first substrate and overlapping the bias electrode; and a liquid crystal layer between the first substrate and the second substrate, the solar cell comprising: a light guide having a first surface and a second surface opposite the first surface and a side surface between the first surface and the second surface; and a light-receiving portion provided along the side surface, wherein the second surface of the solar cell is arranged to face the first substrate of the radio wave reflecting element, and a light receiving surface of the light-receiving portion is arranged on a side of the light guiding portion.
2. 2 . The radio wave reflecting device according to claim 1 , further comprising a functional member, wherein the functional member is disposed on the second surface of the light guide.
3. 3 . The radio wave reflecting device according to claim 2 , wherein the functional member is a reflective diffraction lattice.
4. 4 . The radio wave reflecting device according to claim 2 , wherein the functional member is an optical diffraction layer formed of a liquid crystal material.
5. 5 . The radio wave reflecting device according to claim 2 , wherein the functional member is a light scatterer.
6. 6 . The radio wave reflecting device according to claim 1 , further comprising a wavelength conversion layer as a functional member, wherein the wavelength conversion layer is disposed on the first surface side of the light guide.
7. 7 . The radio wave reflecting device according to claim 1 , wherein a surface of the light guide has an uneven structure.
8. 8 . The radio wave reflecting device according to claim 1 , further comprising fine particles having a different refractive index from the light guide, wherein the fine particles are dispersed in the light guide.
9. 9 . The radio wave reflecting device according to claim 1 , wherein a total thickness of the light guide and the first substrate is equivalent to a quarter of the wavelength of a radio wave incident on the radio wave reflecting element.
10. 10 . The radio wave reflecting device according to claim 1 , wherein a void is provided between the light guide and the first substrate, and a thickness of the void is less than one-tenth of the wavelength of a radio wave incident on the radio wave reflecting element, and a total thickness of the light guide and the first substrate is equivalent to a quarter of the wavelength of a radio wave incident on the radio wave reflecting element.
11. 11 . The radio wave reflecting device according to claim 1 , wherein a void is provided between the light guide and the first substrate, and a thickness of the void is greater than the wavelength of a radio wave incident on the radio wave reflecting element, and each of the light guide and the first substrate has a thickness equivalent to a quarter of the wavelength of a radio wave incident on the radio wave reflecting element.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Continuation of International Patent Application No. PCT/JP2024/024278, filed on Jul. 4, 2024, which claims the benefit of priority to Japanese Patent Application No. 2023-115084, filed on Jul. 13, 2023, the entire contents of each are incorporated herein by reference. FIELD An embodiment of the present invention relates to the configuration of a radio wave reflecting device. BACKGROUND Radio wave reflectors are used to provide radio waves to areas where radio waves are difficult to reach, such as valleys between high-rise buildings (blind zones). As a radio wave reflecting device, for example, a main array element (dipole element), a sub-array element (non-power supply element), and a common electrode (ground electrode) are installed across a dielectric substrate, and the sub-array element is placed close to the main array element (Japanese laid-open patent publication No. 2011-019021) is disclosed. Also disclosed is a configuration in which the array element and the common electrode (grounding electrode) sandwich a dielectric substrate, and the common electrode has a periodic loop shape (Japanese laid-open patent publication No. 2010-226695). A reflector of radio waves using liquid crystals controls the direction of reflection of radio waves by changing the alignment state of the liquid crystals. Since the alignment state of the liquid crystal is controlled by the voltage applied to the liquid crystal, electric power is required to drive the radio wave reflector. When a power supply is available at the location where the radio wave reflector is to be installed and power can be easily secured, there is no problem. However, when the reflector is installed on the exterior wall of a building or in a mountainous area, it may be necessary to secure a new power supply. Photovoltaic power generation can be a candidate as a stand-alone power source, but the installation area will increase when the radio wave reflector and solar cell are placed side by side and placing the radio wave reflector and solar cell on top of each other is expected to affect the radio wave reflection characteristics or the photoelectric conversion efficiency of the solar cell. SUMMARY A radio wave reflecting device in an embodiment according to the present invention includes a radio wave reflecting element and a solar cell. The radio wave reflecting element includes a first substrate provided with bias electrodes arranged in a matrix, a second substrate provided with a common electrode facing the first substrate and overlapping the bias electrode, and a liquid crystal layer between the first substrate and the second substrate. The solar cell includes a light guide having a first surface and a second surface opposite the first surface and a side surface between the first surface and the second surface and a light-receiving portion provided along the side surface. The second surface of the solar cell is arranged to face the first substrate of the radio wave reflecting element, and a light receiving surface of the light-receiving portion is arranged on a side of the light guiding portion. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a plan view of a radio wave reflecting device according to an embodiment of the present invention, viewed from the incident side of the radio wave. FIG. 2 shows a cross-sectional view of the radio wave reflecting device corresponding to the line A1-A2 shown in FIG. 1. FIG. 3A is a plan view of a photovoltaic element used in a radio wave reflecting device according to an embodiment of the present invention. FIG. 3B shows a cross-sectional view of the photovoltaic element corresponding to the line B1-B2 shown in FIG. 3A. FIG. 4 is a plan view of a radio wave reflecting element configured according to an embodiment of the present invention. FIG. 5 is a cross-sectional view of the radio wave reflecting element corresponding to the line C1-C2 shown in FIG. 4. FIG. 6 is a plan view of a radio wave reflecting element configuring a radio wave reflecting device according to an embodiment of the present invention. FIG. 7 is a block diagram illustrating the configuration of the radio wave reflecting device according to an embodiment of the present invention. FIG. 8 is a cross-sectional view of a radio wave reflecting device according to an embodiment of the present invention. FIG. 9 is a cross-sectional view of a radio wave reflecting device according to an embodiment of the present invention. FIG. 10 is a cross-sectional view of a radio wave reflecting device according to an embodiment of the present invention. FIG. 11 is a cross-sectional view of a radio wave reflecting device according to an embodiment of the present invention. FIG. 12 is a cross-sectional view of a radio wave reflecting device according to an embodiment of the present invention. FIG. 13A is a cross-sectional view of a radio wave reflecting device according to an embodiment of the present invention.