Radio wave irradiation device

Abstract

This radio wave irradiation device comprises: a radio wave emission source that emits radio waves; and a radio wave reflection device that is provided on a side wall part of a space for storing an object to be heated, and that reflects the radio waves emitted from the radio wave emission source. The radio wave reflection device includes a plurality of reflection elements arranged in at least one direction. The reflection element includes a patch electrode, a counter electrode facing the patch electrode, and a liquid crystal layer between the patch electrode and the counter electrode.

Description

Radio wave irradiation device

[0001] An embodiment of the present invention relates to a radio wave emitting device capable of controlling the traveling direction of reflected radio waves.

[0002] Heating devices that heat an object by irradiating it with microwaves, such as microwave ovens, are becoming increasingly popular. Microwave ovens use a mechanism that rotates a table on which the object is placed or an antenna that emits microwaves, in order to heat the object efficiently and uniformly.

[0003] However, even in microwave ovens equipped with such a mechanism, regions of high or low microwave intensity may occur due to the shape of the heating chamber. To prevent such regions from occurring, microwave ovens equipped with phase control plates on the side walls of the heating chamber have been disclosed (e.g., Patent Document 1). By changing the capacitance value of the phase control plate, the reflected phase of the microwaves at the side walls is controlled. Technology has been developed to efficiently and uniformly heat an object to be heated by controlling this reflected phase.

[0004] International Publication No. 2018 / 235161

[0005] An object of one embodiment of the present invention is to provide a radio wave irradiation device with a novel configuration that can efficiently and uniformly irradiate an object with radio waves.

[0006] A radio wave irradiation device according to one embodiment of the present invention comprises a radio wave emission source that emits radio waves, and a radio wave reflection device that is provided on a side wall of a space that stores an object to be heated and reflects the radio waves emitted from the radio wave emission source, wherein the radio wave reflection device includes a plurality of reflection elements arranged in at least one direction, and the reflection elements include a patch electrode, a counter electrode that faces the patch electrode, and a liquid crystal layer between the patch electrode and the counter electrode.

[0007] FIG. 1 is a cross-sectional view and functional block diagram showing an overview of a radio wave heating device according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing an overview of a radio wave reflecting device for a radio wave heating device according to one embodiment of the present invention. FIG. 3 is a cross-sectional view showing an attachment structure of a radio wave reflecting device in a radio wave heating device according to one embodiment of the present invention. FIG. 4 is a plan view of a reflector unit cell used in a radio wave reflecting device according to one embodiment of the present invention. FIG. 5 is a cross-sectional structure of a reflector unit cell used in a radio wave reflecting device according to one embodiment of the present invention. FIG. 6 is a diagram showing a state in which no voltage is applied between the patch electrode and the ground electrode in a reflector unit cell used in a radio wave reflecting device according to one embodiment of the present invention. FIG. 7 is a diagram showing a state in which a voltage is applied between the patch electrode and the ground electrode in a reflector unit cell used in a radio wave reflecting device according to one embodiment of the present invention. FIG. 8 is a diagram showing the results of a simulation of the relationship between the thickness of a liquid crystal layer and the phase change of a reflected wave in a radio wave reflecting device according to one embodiment of the present invention. FIG. 9 is a diagram showing the configuration of a radio wave reflecting device according to one embodiment of the present invention. FIG. 10 is a diagram showing a schematic diagram of how the traveling direction of a reflected wave is changed by a radio wave reflecting device according to one embodiment of the present invention. FIG. 11 is a diagram showing the configuration of a radio wave reflecting device according to one embodiment of the present invention. FIG. 12 is a cross-sectional structure of a reflector unit cell in a radio wave reflecting device according to one embodiment of the present invention. FIG. 13 is a cross-sectional view showing an overview of a radio wave reflecting device for a radio wave heating device according to one embodiment of the present invention. FIG. 14 is a plan view showing an overview of a patch electrode of a radio wave heating device according to one embodiment of the present invention.

[0008] 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, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each drawing, components similar to those described above with respect to the previous 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.

[0009] In this specification, unless otherwise specified, the expression that a certain member or region is "on (or under)" another member or region includes not only the case where the member or region is directly above (or directly below) the other member or region, but also the case where the member or region is above (or under) the other member or region. In other words, the above expression also includes the case where another component is included between a certain member or region and the other member or region.

[0010] In this specification, unless otherwise specified, expressions such as "α includes A, B, or C," "α includes any of A, B, and C," and "α includes one selected from the group consisting of A, B, and C" do not exclude cases where α includes multiple combinations of A to C. Furthermore, these expressions do not exclude cases where α includes other elements.

[0011] The following embodiments can be combined with each other as long as no technical contradiction occurs.

[0012] 1 to 10, a radio wave heating device 10 according to one embodiment of the present invention will be described. In the following embodiment, as an example of a radio wave irradiation device, a radio wave heating device that heats an object by irradiating the object with radio waves will be described, but the present invention is not limited to radio wave heating devices. For example, one embodiment of the present invention can be applied to a device for irradiating an object with radio waves for purposes other than heating the object.

[0013] [1-1. Radio wave heating device 10] Fig. 1 is a cross-sectional view and functional block diagram showing an overview of a radio wave heating device according to one embodiment of the present invention. As shown in Fig. 1, the radio wave heating device 10 includes a radio wave reflecting device 100, a heating chamber 200, a radio wave emission source 300, a sensor 400, a control circuit 500, and a drive circuit 600. The control circuit 500 and drive circuit 600 in Fig. 1 are shown to show the connection relationship with other components, and do not mean that the control circuit 500 and drive circuit 600 are arranged outside the heating chamber 200.

[0014] The heating chamber 200 includes a ceiling 210, side walls 220, and a bottom 230. For example, if the planar shapes of the ceiling 210 and the bottom 230 are rectangular, four side walls 220 are provided corresponding to the sides of the rectangle. One of the four side walls 220 includes an openable and closable door.

[0015] The radio wave reflecting device 100 is provided on the side wall 220. The radio wave reflecting device 100 reflects radio waves emitted from a radio wave emission source 300 (described later) in a desired direction. In other words, the radio wave reflecting device 100 can reflect radio waves so that the angle of incidence (θ1) of the radio waves incident on the radio wave reflecting device 100 differs from the angle of reflection (θ2) of the radio waves reflected by the radio wave reflecting device 100. The radio wave reflecting device 100 changes the phase of the radio waves incident on the radio wave reflecting device 100. The direction in which the radio waves are reflected is determined by this change in phase. The radio wave reflecting devices 100 are provided on the left and right side wall 220 when the radio wave heating device 10 is viewed with the door facing forward. However, the radio wave reflecting device 100 may also be provided on the rear side wall 220 or on the door.

[0016] The radio wave source 300 is provided on the ceiling 210 so as to emit radio waves toward the sidewalls 220 and the bottom 230. The radio waves emitted by the radio wave source 300 are between 300 MHz and 300 GHz. These radio waves are called microwaves. For example, the frequency of microwaves used in microwave ovens is 2.4 GHz. However, the radio waves emitted by the radio wave source 300 are not limited to microwaves, and may be radio waves with a frequency less than 300 MHz or higher than 300 GHz. The size and pitch of the patch electrode 108 are determined depending on the frequency of the radio waves. The radio wave source 300 may be, but is not limited to, an antenna, a magnetron, or a waveguide.

[0017] The heating object 310 is stored in a space defined by the ceiling portion 210, the sidewall portion 220, and the bottom portion 230. In Fig. 1 , the heating object 310 is placed on the bottom portion 230. The heating object 310 may be placed directly on the bottom portion 230, or may be placed on a stage provided on the bottom portion 230.

[0018] The sensor 400 is provided on the ceiling 210 so as to be able to detect the position of the heating object 310. The sensor 400 may have a temperature detection function in addition to a position detection function. That is, the sensor 400 may detect high-temperature areas and low-temperature areas of the heating object 310. The sensor 400 may be provided on the side wall 220 or the bottom 230.

[0019] The control circuit 500 is connected to the sensor 400. Detection information of the heating object 310 detected by the sensor 400 is transmitted to the control circuit 500. The control circuit 500 calculates position information (or position information and temperature information) of the heating object 310 in the heating chamber 200 based on the detection information received from the sensor 400.

[0020] The drive circuit 600 is connected to the control circuit 500 and the radio wave reflecting device 100. The drive circuit 600 drives the radio wave reflecting device 100 based on position information calculated by the control circuit 500. That is, the control circuit 500 controls the drive circuit 600 based on position information of the object 310 to be heated detected by the sensor 400. Specifically, the control circuit 500 controls the drive circuit 600 so that radio waves emitted from the radio wave emission source 300 toward the radio wave reflecting device 100 and reflected by the radio wave reflecting device 100 are directed toward the object 310 to be heated detected by the sensor 400. For example, as shown in FIG. 1 , the control circuit 500 controls the drive circuit 600 so that the incident angle θ1 and the reflection angle θ2 with respect to the radio wave reflecting device 100 are different for the radio waves emitted from the radio wave emission source 300 toward the radio wave reflecting device 100 on the right side of FIG. 1 .

[0021] [1-2. Radio Wave Reflecting Device 100] FIG. 2 is a cross-sectional view showing an outline of a radio wave reflecting device of a radio wave heating device according to one embodiment of the present invention. As shown in FIG. 2, the radio wave reflecting device 100 includes a plurality of reflecting elements (reflector unit cells 102). The plurality of reflector unit cells 102 are arranged in at least one direction. In FIG. 2, the plurality of reflector unit cells 102 are arranged in the Y-axis direction. The radio wave reflecting device 100 includes a dielectric substrate 104, a counter substrate 106, a patch electrode 108, a ground electrode (counter electrode) 110, a liquid crystal layer 114, a sealant 128, a switching element 134, a terminal portion 126, and a printed circuit board (FPC) 160. The liquid crystal layer 114 contains liquid crystal molecules 116. A passivation layer 158 is provided between the patch electrode 108 and the dielectric substrate 104. Details will be described later, but if the radio wave reflecting device 100 is a two-axis reflection control device, the radio wave reflecting device 100 includes a switching element 134, but if the radio wave reflecting device 100 is a one-axis reflection control device, the radio wave reflecting device 100 does not need to include a switching element 134.

[0022] Each reflector unit cell 102 includes at least a patch electrode 108, a ground electrode 110, a liquid crystal layer 114, and a switching element 134. The patch electrode 108 is provided individually for each reflector unit cell 102. The patch electrode 108 is provided on the dielectric substrate 104 side. The ground electrode 110 faces the patch electrode 108 and is provided in common to the plurality of reflector unit cells 102. The ground electrode 110 is provided on the counter substrate 106 side.

[0023] The counter substrate 106 is disposed at a position close to the side wall portion 220 with respect to the dielectric substrate 104. In other words, the dielectric substrate 104 is provided inside the heating chamber 200 or at a position close to the radio wave emission source 300 with respect to the counter substrate 106. Similarly, the patch electrode 108 is provided at a position close to the radio wave emission source 300 with respect to the ground electrode 110. Although FIG. 2 illustrates a configuration in which the counter substrate 106 is provided so as to be in contact with the side wall portion 220, the configuration is not limited to this. For example, another member may be provided between the counter substrate 106 and the side wall portion 220.

[0024] The liquid crystal layer 114 is provided between the patch electrode 108 and the ground electrode 110. The orientation of the liquid crystal molecules 116 contained in the liquid crystal layer 114 is controlled by voltages supplied to the patch electrode 108 and the ground electrode 110. A sealant 128 is provided to surround the periphery of the counter substrate 106. In other words, the liquid crystal layer 114 is sealed by the sealant 128. The patch electrode 108 and the ground electrode 110 are provided in an area surrounded by the sealant 128.

[0025] The radio wave reflecting device 100 is divided into a radio wave reflecting area 162 and a peripheral area 164 surrounding the radio wave reflecting area 162. A patch electrode 108 and a ground electrode 110 are arranged in the radio wave reflecting area 162. Radio waves incident on the radio wave reflecting device 100 from the dielectric substrate 104 side are reflected by the radio wave reflecting area 162. When the radio waves are reflected, the direction of travel of the reflected radio waves can be controlled by controlling the voltage supplied between the patch electrode 108 and the ground electrode 110 and controlling the orientation of the liquid crystal molecules 116. Although not shown, a part of the drive circuit 600 is arranged in the peripheral area 164.

[0026] The switching element 134 is connected to the patch electrode 108. The switching element 134 is provided at a position close to the radio wave emission source 300 with respect to the patch electrode 108. The switching element 134 is driven by a drive circuit 600 (see FIG. 1 ). The orientation of the liquid crystal molecules 116 is controlled according to the drive state of the switching element 134. As will be described in detail later, by controlling the orientation of the liquid crystal molecules 116, the phase of the radio wave reflected by the radio wave reflecting device 100 is controlled. By controlling the phase of the radio wave, the traveling direction of the reflected radio wave is controlled.

[0027] The terminal portion 126 is provided at an end of the dielectric substrate 104. The terminal portion 126 may be configured in the same layer as the patch electrode 108. The terminal portion 126 may be configured in the same layer as part or all of the conductive layer that configures the switching element 134. The terminal portion 126 is connected to the switching element 134 via wiring. An FPC 160 is connected to the terminal portion 126. A drive circuit 600 drives the switching element 134 in response to a control signal input from the outside via the FPC 160.

[0028] [1-3. Mounting Structure of Radio Wave Reflecting Device 100] Figure 3 is a cross-sectional view showing the mounting structure of a radio wave reflecting device in a radio wave heating device according to one embodiment of the present invention. For ease of explanation, Figure 3 only shows the dielectric substrate 104, the opposing substrate 106, the patch electrode 108, the terminal portion 126, the switching element 134, and the FPC 160 of the radio wave reflecting device 100 in Figure 2. In addition to the above configuration, Figure 3 also shows a drive circuit 600 provided on the dielectric substrate 104. The drive circuit 600 is provided in the peripheral region 164, similar to the terminal portion 126. The drive circuit 600 is mounted on the dielectric substrate 104, for example, in the form of a chip-on-glass (COG) structure.

[0029] 3 , radio wave shielding members 320 for shielding radio waves emitted from the radio wave emission source 300 are provided between the terminal unit 126 and the radio wave emission source 300, between the switching element 134 and the radio wave emission source 300, and between the drive circuit 600 and the radio wave emission source 300. The radio wave shielding members 320 are provided in positions close to the radio wave emission source 300 relative to the terminal unit 126, the switching element 134, and the drive circuit 600. Because the radio waves emitted from the radio wave emission source 300 are shielded by the radio wave shielding member 320, adverse effects such as heat generation in the terminal unit 126, the switching element 134, and the drive circuit 600 due to irradiation of the radio waves can be suppressed. Instead of the radio wave shielding member 320, a radio wave absorbing member that absorbs radio waves may be used.

[0030] 3 illustrates a configuration in which the radio wave shielding member 320 is provided for all of the terminal portion 126, the switching element 134, and the drive circuit 600, but the embodiment of the present invention is not limited to this configuration. The radio wave shielding member 320 may be provided for at least some of the terminal portion 126, the switching element 134, and the drive circuit 600. For example, if the switching element 134 is not adversely affected by radio waves emitted from the radio wave emission source 300, the radio wave shielding member 320 for the switching element 134 may be omitted.

[0031] 3 , the FPC 160 penetrates the side wall portion 220 and is drawn out to the outside of the heating chamber 200. The FPC 160 drawn out to the outside of the heating chamber 200 is connected to a control circuit 500 provided outside the heating chamber 200. The control circuit 500 and the drive circuit 600 are electrically connected by wiring connected to the FPC 160 and the terminal portion 126.

[0032] In the case of two-axis reflection control, which will be described later, the switching element 134 is provided in the radio wave reflection region 162, and therefore, as described above, the radio wave shielding member 320 is provided at a position corresponding to the switching element 134. On the other hand, in the case of one-axis reflection control, which will be described later, in which the switching element 134 is not provided in the radio wave reflection region 162, the radio wave shielding member 320 is provided at a position corresponding to the terminal portion 126 and the drive circuit 600 in the peripheral region 164, and the radio wave shielding member 320 does not necessarily have to be provided in the radio wave reflection region 162.

[0033] 4A and 4B show a reflector unit cell 102 used in a radio wave reflecting device according to one embodiment of the present invention. Fig. 4A shows a plan view of the reflector unit cell 102 as seen from above (the side onto which radio waves are incident), and Fig. 4B shows a cross-sectional view taken along line A1-A2 in the plan view.

[0034] As shown in Figures 4A and 4B, the reflector unit cell 102 includes a dielectric substrate 104, a counter substrate 106, a patch electrode 108, a ground electrode 110, a liquid crystal layer 114, a first alignment film 112a, and a second alignment film 112b. Within the reflector unit cell 102, the dielectric substrate 104 may be considered as a single layer (dielectric layer). The patch electrode 108 is provided on the dielectric substrate (dielectric layer) 104, and the ground electrode 110 is provided on the counter substrate 106. A first alignment film 112a is provided on the dielectric substrate (dielectric layer) 104 to cover the patch electrode 108. A second alignment film 112b is provided on the counter substrate 106 to cover the ground electrode 110. The patch electrode 108 and the ground electrode 110 are arranged opposite each other, with a liquid crystal layer 114 between them. The first alignment film 112a is interposed between the patch electrode 108 and the liquid crystal layer 114. A second alignment film 112 b is interposed between the ground electrode 110 and the liquid crystal layer 114 .

[0035] The patch electrode 108 preferably has a shape that is symmetrical with respect to the vertically and horizontally polarized waves of the incident radio wave. For example, the patch electrode 108 has a square or circular shape in a plan view. FIG. 4A shows a case where the patch electrode 108 is square in a plan view. The shape of the ground electrode 110 is not particularly limited, and it has a shape that extends over substantially the entire surface of the opposing substrate 106 so as to have a larger area than the patch electrode 108. The materials for forming the patch electrode 108 and the ground electrode 110 are not particularly limited. The patch electrode 108 and the ground electrode 110 are formed using a conductive metal or metal oxide. A first wiring 118 may be provided on the dielectric substrate (dielectric layer) 104. The first wiring 118 is connected to the patch electrode 108. The first wiring 118 is used when a control signal is supplied to the patch electrode 108. When multiple reflector unit cells are arranged, the first wiring 118 is used to connect a patch electrode to an adjacent patch electrode.

[0036] Although not shown in FIGS. 4A and 4B , the dielectric substrate (dielectric layer) 104 and the counter substrate 106 are bonded together with a sealant 128. The dielectric substrate (dielectric layer) 104 and the counter substrate 106 are disposed opposite each other with a gap therebetween. The liquid crystal layer 114 is provided within the area surrounded by the sealant 128. The liquid crystal layer 114 is provided so as to fill the gap between the dielectric substrate (dielectric layer) 104 and the counter substrate 106. The distance between the dielectric substrate (dielectric layer) 104 and the counter substrate 106 is greater than 0.5 mm, or equal to or greater than 0.6 mm. A patch electrode 108, a ground electrode 110, a first alignment film 112 a, and a second alignment film 112 b are provided between the dielectric substrate (dielectric layer) 104 and the counter substrate 106. Therefore, to be precise, the distance between the first alignment film 112a and the second alignment film 112b provided on the dielectric substrate 104 and the counter substrate 106, respectively, is the thickness of the liquid crystal layer 114. Although not shown in Fig. 4B, a spacer may be provided between the dielectric substrate (dielectric layer) 104 and the counter substrate 106 to keep the distance constant.

[0037] A control signal that controls the orientation of the liquid crystal molecules 116 in the liquid crystal layer 114 is supplied to the patch electrode 108. The control signal is a DC voltage signal or a polarity inversion signal in which positive and negative DC voltages alternate. In the latter case, the ground electrode 110 is supplied with a ground level or a voltage at an intermediate level of the polarity inversion signal. Supplying the control signal to the patch electrode 108 changes the orientation state of the liquid crystal molecules in the liquid crystal layer 114. A liquid crystal material having dielectric anisotropy is used for the liquid crystal layer 114. For example, nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, or discotic liquid crystal can be used for the liquid crystal layer 114. The dielectric constant of the liquid crystal layer 114 with dielectric anisotropy changes depending on the change in the orientation state of the liquid crystal molecules. The reflector unit cell 102 can change the dielectric constant of the liquid crystal layer 114 by the control signal supplied to the patch electrode 108, thereby delaying the phase of the reflected wave when reflecting radio waves.

[0038] The frequency band of radio waves reflected by the reflector unit cell 102 is the microwave (SHF: Super High Frequency) band. The orientation of the liquid crystal molecules 116 in the liquid crystal layer 114 changes in response to a control signal supplied to the patch electrode 108, but the orientation of the liquid crystal molecules 116 hardly follows the frequency of the radio waves irradiated onto the patch electrode 108. Therefore, the reflector unit cell 102 is not affected by the radio waves and can control the phase of the reflected radio waves.

[0039] FIG. 5A shows a state (referred to as the "first state") in which no voltage is applied between the patch electrode 108 and the ground electrode 110. FIG. 5A shows a case in which the first alignment film 112a and the second alignment film 112b are horizontal alignment films. In the first state, the long axes of the liquid crystal molecules 116 are aligned horizontally relative to the surfaces of the patch electrode 108 and the ground electrode 110 by the first alignment film 112a and the second alignment film 112b. FIG. 5B shows a state (referred to as the "second state") in which a control signal (voltage signal) is applied to the patch electrode 108. In the second state, the liquid crystal molecules 116 are subjected to the action of an electric field, and their long axes are aligned perpendicular to the surfaces of the patch electrode 108 and the ground electrode 110. The angle at which the long axes of the liquid crystal molecules 116 are aligned can be set to a direction intermediate between the horizontal and vertical directions, depending on the magnitude of the control signal applied to the patch electrode 108 (the magnitude of the voltage between the counter electrode and the patch electrode).

[0040] When the liquid crystal molecules 116 have a positive dielectric anisotropy, the dielectric constant is larger in the second state than in the first state. On the other hand, when the liquid crystal molecules 116 have a negative dielectric anisotropy, the apparent dielectric constant is smaller in the second state than in the first state. The liquid crystal layer 114 having dielectric anisotropy can also be regarded as a variable dielectric layer. The reflector unit cell 102 can control the phase delay (or non-delay) of the reflected wave by utilizing the dielectric anisotropy of the liquid crystal layer 114.

[0041] The reflector unit cell 102 is used as a reflector that reflects radio waves in a predetermined direction. It is preferable that the amplitude of the radio waves reflected by the reflector unit cell 102 is attenuated as little as possible. As is clear from the structure shown in FIG. 4B , when radio waves propagating through the air are reflected by the reflector unit cell 102, the radio waves pass through the dielectric substrate (dielectric layer) 104 twice. The dielectric substrate (dielectric layer) 104 is formed of a dielectric material such as glass or resin. When radio waves pass through a dielectric, the phase velocity of the radio waves changes. Therefore, in order to prevent attenuation of the amplitude of the reflected wave, it is preferable that the thickness of the dielectric substrate (dielectric layer) 104 be set to a thickness equivalent to one-quarter of the wavelength of the radio waves being reflected.

[0042] FIG. 6 shows the results of a simulation of the relationship between the thickness of the liquid crystal layer and the phase change of the reflected wave in a radio wave reflecting device according to one embodiment of the present invention. The simulation shown in FIG. 6 was performed with a plurality of reflector unit cells 102 arranged, assuming a plate-shaped radio wave reflecting device. In the simulation, the microwave frequency was set to 2.4 GHz, the size of the patch electrode 108 in the reflector unit cell 102 was 36 mm x 36 mm, and the patch electrodes 108 of this size were arranged at a pitch of 50 mm. In the simulation, the thickness t of the liquid crystal layer 114 in the reflector unit cell 102 was used as a parameter. This simulation was performed using CST Studio Suite (manufactured by Dassault Systèmes).

[0043] FIG. 6 shows three graphs in the vertical direction. In each graph, the vertical axis represents phase, and the horizontal axis represents frequency. The top graph represents simulation results calculated under the condition that the thickness t of the liquid crystal layer 114 is 0.5 mm. The middle graph represents simulation results calculated under the condition that the thickness t of the liquid crystal layer 114 is 0.6 mm. The bottom graph represents simulation results calculated under the condition that the thickness t of the liquid crystal layer 114 is 1.0 mm. Although not shown, the simulation results calculated under the conditions that the thickness t of the liquid crystal layer 114 is 0.7 mm, 0.8 mm, and 0.9 mm are substantially the same as the simulation results calculated under the condition that the thickness t of the liquid crystal layer 114 is 0.6 mm and 1.0 mm.

[0044] Each of the top, middle, and bottom graphs shows three simulation results. The three simulation results are for cases where the relative dielectric constant of the liquid crystal layer 114 is different (relative dielectric constant ε = 2.5, 3.0, 3.5). Different relative dielectric constants ε mean different orientations of the liquid crystal molecules 116 in the radio wave reflecting device 100. In other words, at a frequency of 2.4 GHz, the relatively large phase difference between conditions with different relative dielectric constants ε means that the reflection angle when reflecting microwaves can be changed relatively greatly.

[0045] In other words, the reflection angle when reflecting microwaves can be changed more greatly when the thickness t of the liquid crystal layer 114 is 0.6 mm than when the thickness t of the liquid crystal layer 114 is 0.5 mm. Therefore, when the thickness t of the liquid crystal layer 114 is greater than 0.5 mm, the radio wave reflecting device 100 can rapidly increase the reflection angle of microwaves. Alternatively, when the thickness t of the liquid crystal layer 114 is 0.6 mm or greater, the radio wave reflecting device 100 can rapidly increase the reflection angle of microwaves.

[0046] As described above, according to the radio wave heating device 10 of this embodiment, the radio wave reflection device 100 can change the reflection angle of the radio waves emitted from the radio wave emission source 300. Therefore, by adjusting the reflection angle of the radio waves according to the position and size of the object 310 to be heated, it is possible to efficiently and uniformly irradiate the object 310 with radio waves. As a result, it is possible to efficiently and uniformly heat the object 310 to be heated.

[0047] In the present embodiment, a configuration has been exemplified in which the reflection angle of the radio wave reflecting device 100 is controlled based on the position information of the heating object 310 detected by the sensor 400, but the present invention is not limited to this configuration. For example, the control circuit 500 may control the drive circuit 600 so that the radio waves reflected by the radio wave reflecting device 100 are irradiated over the entire area of ​​the heating chamber 200.

[0048] 7 to 10, a radio wave reflecting device 100 in which reflector unit cells 102 are integrated will be described. The radio wave reflecting device 100 is available in a single-axis reflection control system and a dual-axis reflection control system. Each control system will be described below.

[0049] [1-5-1. Radio Wave Reflecting Device A (Single-Axis Reflection Control)] FIG. 7 shows the configuration of a radio wave reflecting device 100a according to one embodiment of the present invention. The radio wave reflecting device 100a includes a reflector 120. The reflector 120 is composed of a plurality of reflector unit cells 102. The plurality of reflector unit cells 102 are arranged, for example, in a first direction (the X-axis direction shown in FIG. 7 ) and a second direction (the Y-axis direction shown in FIG. 7 ) intersecting the first direction. The reflector unit cells 102 are arranged so that the patch electrodes 108 face the radio wave incident surface. The reflector 120 is flat, and a plurality of patch electrodes 108 are arranged in a matrix within the flat surface. The radio wave reflecting device 100a (single-axis reflection control) shown in FIG. 7 does not necessarily include a switching element 134.

[0050] The radio wave reflecting device 100 has a structure in which multiple reflector unit cells 102 are integrated on a single dielectric substrate (dielectric layer) 104. As shown in FIG. 7 , the radio wave reflecting device 100 has a structure in which the dielectric substrate (dielectric layer) 104 on which multiple patch electrodes 108 are arranged and the counter substrate 106 on which a ground electrode 110 is provided are stacked, with a liquid crystal layer 114 provided between the two substrates. The reflector 120 is formed in the area where the multiple patch electrodes 108 and the ground electrode 110 overlap. For each patch electrode 108, the cross-sectional structure of the reflector 120 is the same as the structure of the reflector unit cell 102 shown in FIG. 4B . The dielectric substrate (dielectric layer) 104 and the counter substrate 106 are bonded together with a sealant 128, and the liquid crystal layer 114 is provided in the area inside the sealant 128.

[0051] The dielectric substrate (dielectric layer) 104 has a thickness equivalent to one-quarter of the wavelength of the reflected radio wave. In addition to the region facing the opposing substrate 106, the dielectric substrate (dielectric layer) 104 has a peripheral region 122 extending outward from the opposing substrate 106. A first drive circuit 124 and a terminal section 126 are provided in the peripheral region 122. The first drive circuit 124 outputs a control signal to the patch electrode 108. In this configuration, the first drive circuit 124 corresponds to the drive circuit 600. The terminal section 126 is a region for forming a connection with an external circuit, and an FPC 160 is connected to the terminal section 126. A signal for controlling the first drive circuit 124 is input to the terminal section 126.

[0052] As described above, a plurality of patch electrodes 108 are arranged in the first direction (X-axis direction) and the second direction (Y-axis direction) on the dielectric substrate (dielectric layer) 104. A plurality of first wirings 118 extending in the second direction (Y-axis direction) are disposed on the dielectric substrate (dielectric layer) 104. Each of the plurality of first wirings 118 is electrically connected to a plurality of patch electrodes 108 arranged in the second direction (Y-axis direction). In other words, the plurality of patch electrodes 108 arranged in the second direction (Y-axis direction) are connected by the first wirings 118. The reflector 120 has a configuration in which a plurality of patch electrode arrays connected by the first wirings 118 are arranged in a row in the first direction (X-axis direction).

[0053] The plurality of first wirings 118 arranged on the reflector 120 extend into the peripheral region 122 and are connected to a first drive circuit 124. The first drive circuit 124 outputs control signals to be supplied to the patch electrodes 108. The first drive circuit 124 is capable of outputting control signals of different voltage levels to each of the plurality of first wirings 118. As a result, on the reflector 120, a control signal is supplied to the plurality of patch electrodes 108 arranged in the first direction (X-axis direction) and the second direction (Y-axis direction) for each column (for each patch electrode 108 arranged in the second direction (Y-axis direction)).

[0054] In the radio wave reflecting device 100a, a control signal is supplied to each set of the multiple patch electrodes 108 arranged in the second direction (Y-axis direction), thereby controlling the reflection direction of the reflected wave of the radio wave incident on the reflector 120. In other words, the radio wave reflecting device 100a can control the propagation direction of the reflected wave of the radio wave irradiated to the reflector 120 in the left-right direction in the drawing, centered on a reflection axis RY parallel to the second direction (Y-axis direction).

[0055] 8 schematically shows how the propagation direction of a reflected wave changes depending on the two reflector unit cells 102. When radio waves are incident on the first reflector unit cell 102a and the second reflector unit cell 102b in the same phase and different control signals (V1≠V2) are supplied to the first reflector unit cell 102a and the second reflector unit cell 102b, respectively, the phase change of the reflected wave by the second reflector unit cell 102b is larger than that of the first reflector unit cell 102a. As a result, the phase of the reflected wave R1 reflected by the first reflector unit cell 102a differs from the phase of the reflected wave R2 reflected by the second reflector unit cell 102b (in FIG. 8, the phase of the reflected wave R2 leads the phase of the reflected wave R1), and the propagation direction of the reflected wave apparently changes obliquely.

[0056] In Fig. 7 , the multiple patch electrodes 108 arranged in the second direction (Y-axis direction) are electrically connected by the first wiring 118 and are electrically equipotential. Therefore, it is possible to replace the multiple divided shapes with a continuous strip-shaped electrode in the second direction (Y-axis direction). However, because the appropriate size range of the patch electrode 108 depends on the wavelength of the radio wave to be reflected, if the patch electrode 108 is strip-shaped, the sensitivity to the target wavelength will decrease and the behavior for vertically polarized waves and horizontally polarized waves will differ. Therefore, as shown in Fig. 7 , it is preferable that each patch electrode 108 has a shape that is symmetrical with respect to vertically polarized waves and horizontally polarized waves (although the patch electrode 108 has a square shape in Fig. 7 , the patch electrode 108 may also have a circular shape), the multiple patch electrodes 108 are arranged in an array, and the multiple patch electrodes 108 arranged parallel to the reflection axis RY are connected by the first wiring 118.

[0057] Although not shown, the thickness of the dielectric substrate (dielectric layer) 104 of the radio wave reflecting device 100a shown in Fig. 7 is equivalent to a quarter wavelength of the target radio wave, thereby suppressing attenuation of the amplitude of the reflected wave reflected by the radio wave reflecting device 100.

[0058] [1-5-2. Radio wave reflecting device B (two-axis reflection control)] The radio wave reflecting device 100a described above has a single reflection axis RY, so it is possible to control the reflection angle in the direction around the reflection axis RY as the axis of rotation. The radio wave reflecting device 100b described below is capable of two-axis reflection control. The following explanation will focus on the differences from the radio wave reflecting device 100a described above.

[0059] 9 shows the configuration of a radio wave reflecting device 100b according to this embodiment. The following description will focus on the differences from the radio wave reflecting device 100a shown in FIG.

[0060] The radio wave reflecting device 100b includes a reflector 120 having a plurality of first wirings 118 extending in the second direction (Y-axis direction) and a plurality of second wirings 132 extending in the first direction (X-axis direction). The plurality of first wirings 118 and the plurality of second wirings 132 are arranged to intersect with an insulating layer (not shown) sandwiched therebetween. The plurality of first wirings 118 are connected to a first drive circuit 124, and the plurality of second wirings 132 are connected to a second drive circuit 130. The first drive circuit 124 outputs control signals, and the second drive circuit 130 outputs scanning signals. In this configuration, the first drive circuit 124 and the second drive circuit 130 correspond to a drive circuit 600. In FIG. 9 , the first drive circuit 124 is shown as having an IC chip or the like mounted on the dielectric substrate 104. The second drive circuit 130 is shown as a drive circuit using thin film transistors formed on the dielectric substrate 104, similar to the switching elements 134, but is not limited thereto.

[0061] 9 shows an enlarged inset of the arrangement of the four patch electrodes 108 and the two first wirings 118 and second wirings 132. Each of the four patch electrodes 108 is provided with a switching element 134. The switching (on and off) of the switching element 134 is controlled by a scanning signal supplied to the second wiring 132. When the switching element 134 is turned on, the patch electrode 108 is electrically connected to the first wiring 118, and a control signal is supplied to that patch electrode 108. The switching element 134 is formed of, for example, a thin-film transistor. With this configuration, it is possible to select a plurality of patch electrodes 108 arranged in the first direction (X-axis direction) row by row, and supply control signals of different voltage levels to each row.

[0062] 9 can control the direction of travel of the reflected wave, which is irradiated onto the reflector 120, in the left-right direction of the drawing about a reflection axis VR parallel to the second direction (Y-axis direction), and can also control the direction of travel of the reflected wave in the up-down direction of the drawing about a reflection axis HR parallel to the first direction (X-axis direction). In other words, the radio wave reflecting device 100 has a reflection axis VR parallel to the second direction (Y-axis direction) and a reflection axis VH parallel to the first direction (X-axis direction), and therefore can control the reflection angle in the direction about the reflection axis VR as the rotation axis and in the direction about the reflection axis HR as the rotation axis.

[0063] FIG. 10 shows an example of the cross-sectional structure of a reflector unit cell 102 in which a switching element 134 is connected to a patch electrode 108. The switching element 134 is provided on a dielectric substrate (dielectric layer) 104. The switching element 134 is a transistor and has a stacked structure of a first gate electrode 138, a second gate insulating layer 146, a semiconductor layer 142, a second gate insulating layer 146, and a second gate electrode 148. An undercoat layer 136 may be provided between the first gate electrode 138 and the dielectric substrate (dielectric layer) 104. A first wiring 118 is provided between the first gate insulating layer 140 and the second gate insulating layer 146. The first wiring 118 is provided so as to be in contact with the semiconductor layer 142. A first connection wiring 144 is provided in the same layer as the conductive layer that forms the first wiring 118. The first connection wiring 144 is provided so as to be in contact with the semiconductor layer 142. The connection structure of the first wiring 118 and the first connection wiring 144 to the semiconductor layer 142 shows a structure in which one wiring is connected to the source of the transistor and the other wiring is connected to the drain.

[0064] A first interlayer insulating layer 150 is provided to cover the switching element 134. A second wiring 132 is provided below the first interlayer insulating layer 150. The second wiring 132 is connected to the second gate electrode 148 through a contact hole formed in the first interlayer insulating layer 150. Although not shown, the first gate electrode 138 and the second gate electrode 148 are electrically connected to each other in a region that does not overlap with the semiconductor layer 142. A second connection wiring 152 is provided below the first interlayer insulating layer 150 and is made of the same conductive layer as the second wiring 132. The second connection wiring 152 is connected to the first connection wiring 144 through a contact hole formed in the first interlayer insulating layer 150.

[0065] A second interlayer insulating layer 154 is provided to cover the second wiring 132 and the second connection wiring 152. Furthermore, a planarizing layer 156 is provided to fill in the step of the switching element 134. By providing the planarizing layer 156, the patch electrode 108 can be formed without being affected by the placement of the switching element 134. A passivation layer 158 is provided below the flat surface of the planarizing layer 156. The patch electrode 108 is provided below the passivation layer 158. The patch electrode 108 is connected to the second connection wiring 152 via a contact hole that penetrates the passivation layer 158, the planarizing layer 156, and the second interlayer insulating layer 154. A first alignment film 112a is provided below the patch electrode 108.

[0066] The counter substrate 106 includes a ground electrode 110 and a second alignment film 112b, as in FIG. 4B . The dielectric substrate (dielectric layer) 104 and the counter substrate are arranged so that the surface of the dielectric substrate (dielectric layer) 104 on which the switching element 134 and the patch electrode 108 are provided faces the surface of the counter substrate on which the ground electrode 110 is provided. A liquid crystal layer 114 is provided between these substrates. The thickness t of the liquid crystal layer 114 can be defined as the length from the surface of the patch electrode 108 on the liquid crystal layer 114 side to the surface of the ground electrode 110 on the liquid crystal layer 114 side. In this case, the thickness t of the liquid crystal layer 114 may include the thickness of at least one insulating layer (undercoat layer 136, first gate insulating layer 140, second gate insulating layer 146, first interlayer insulating layer 150, second interlayer insulating layer 154, planarizing layer 156, passivation layer 158) between the patch electrode 108 and the dielectric substrate (dielectric layer) 104.

[0067] The layers formed on the dielectric substrate (dielectric layer) 104 are formed using the following materials. The undercoat layer 136 is formed, for example, of a silicon oxide film. The first gate insulating layer 140 and the second gate insulating layer 146 are formed, for example, of a silicon oxide film or a stacked structure of a silicon oxide film and a silicon nitride film. The semiconductor layer is formed of an oxide semiconductor including a silicon semiconductor such as amorphous silicon or polycrystalline silicon, or a metal oxide such as indium oxide, zinc oxide, or gallium oxide. The first gate electrode 138 and the second gate electrode 148 may be formed, for example, of molybdenum (Mo), tungsten (W), or an alloy thereof. The first wiring 118, the second wiring 132, the first connection wiring 144, and the second connection wiring 152 are formed using a metal material such as titanium (Ti), aluminum (Al), or molybdenum (Mo). For example, the gate electrode and wiring may be formed of a titanium (Ti) / aluminum (Al) / titanium (Ti) laminated structure or a molybdenum (Mo) / aluminum (Al) / molybdenum (Mo) laminated structure. The planarization layer 156 is formed of a resin material such as acrylic or polyimide. The passivation layer 158 is formed of, for example, a silicon nitride film. The patch electrode 108 and the ground electrode 110 are formed of a metal film such as aluminum (Al) or copper (Cu), or a transparent conductive film such as indium tin oxide (ITO).

[0068] 10 , the second wiring 132 is connected to the gate of a transistor used as a switching element 134, the first wiring 118 is connected to one of the source and drain of the transistor, and the patch electrode 108 is connected to the other of the source and drain, thereby enabling a predetermined patch electrode to be selected from the plurality of patch electrodes 108 arranged in a matrix and supplied with a control signal. Furthermore, by providing a switching element 134 to each patch electrode 108 in the reflector 120, a control voltage can be supplied to each patch electrode 108 arranged in a horizontal row along the first direction (X-axis direction) or each patch electrode 108 arranged in a vertical row along the second direction (Y-axis direction). With this configuration, for example, when the reflector 120 is upright, the reflection direction of the reflected wave can be controlled in the left-right and up-down directions.

[0069] [1-6. Effect of Microwaves on Liquid Crystal Layer 114] When the radio waves used in the microwave heating device 10 are microwaves (frequency=2.4 GHz), the effect of the microwaves on the liquid crystal layer 114 will be described.

[0070] The microwave power P absorbed by a dielectric is expressed by the following formula: P = K·ε ｒ ・tanδ・f・E ２ [W / cm ３ The parameters are as follows: K: 0.556×10 －１０ ε ｒ : relative dielectric constant of dielectric tanδ: dielectric loss angle of dielectric f: frequency [Hz] E: electric field strength [V / m]

[0071] Considering the microwave power P for water, glass, and liquid crystal, the ε ｒ and the value of tan δ is the ε of water ｒ and tanδ, and the ε ｒ and tan δ. Therefore, even if the liquid crystal layer 114 is used in the radio wave reflecting device 100 in the microwave heating device 10 using microwaves, the liquid crystal layer 114 is hardly heated by the microwaves.

[0072] [2. Second embodiment] A radio wave heating device 10C according to one embodiment of the present invention will be described with reference to Figures 11 and 12. The configuration of the radio wave heating device 10C according to the second embodiment is similar to the configuration of the radio wave heating device 10 according to the first embodiment. In the following description, a description of the configuration that is the same as that of the radio wave heating device 10 will be omitted, and only configurations that differ from the radio wave heating device 10 will be described. In the following description, when a configuration that is the same as that of the first embodiment is described, reference will be made to Figures 1 to 10, and the alphabet "C" will be added after the reference numerals shown in Figures 1 to 10.

[0073] [2-1. Radio Wave Reflecting Device 100C] FIG. 11 is a cross-sectional view showing an outline of a radio wave reflecting device for a radio wave heating device according to one embodiment of the present invention. As shown in FIG. 11, the radio wave reflecting device 100C includes a plurality of reflecting elements (reflector unit cells) 102C. The plurality of reflector unit cells 102C are arranged in at least one direction. In FIG. 11, the plurality of reflector unit cells 102C are arranged in the Y-axis direction. The radio wave reflecting device 100C includes a dielectric substrate 104C, a counter substrate 106C, a drive electrode 109C, a patch electrode (counter electrode) 111C, a liquid crystal layer 114C, a sealant 128C, a switching element 134C, a terminal portion 126C, and an FPC 160C. The liquid crystal layer 114C contains liquid crystal molecules 116C. In this configuration, the electrode 111C provided on the counter substrate 106C side functions as a patch electrode that reflects radio waves. The liquid crystal is oriented and the dielectric constant changes depending on the potential difference between the potential applied to the drive electrode 109C and the potential applied to the patch electrode 111C. A passivation layer 158C is provided between the drive electrode 109C and the dielectric substrate 104C.

[0074] Each reflector unit cell 102C includes at least a drive electrode 109C, a patch electrode 111C, a liquid crystal layer 114C, and a switching element 134C. In FIG. 11 , the patch electrode 111C appears to be provided individually for each reflector unit cell 102C, but in reality, as shown in FIG. 12 , the patch electrode 111C is provided commonly to multiple reflector unit cells 102C. The drive electrode 109C is provided on the dielectric substrate 104C side. The drive electrode 109C faces the patch electrode 111C and is provided individually for each reflector unit cell 102C. The patch electrode 111C is provided on the counter substrate 106C side.

[0075] The dielectric substrate 104C is disposed in a position close to the sidewall 220C relative to the counter substrate 106C. In other words, the counter substrate 106C is provided inside the heating chamber 200C or in a position close to the radio wave emission source 300C relative to the dielectric substrate 104C. Similarly, the patch electrode (counter electrode) 111C is provided in a position close to the radio wave emission source 300C relative to the drive electrode 109C. While FIG. 11 illustrates a configuration in which the dielectric substrate 104C is provided in contact with the sidewall 220C, the configuration is not limited to this. For example, another member may be provided between the dielectric substrate 104C and the sidewall 220C.

[0076] The switching element 134C is connected to the drive electrode 109C. The switching element 134C is located far from the radio wave emission source 300C relative to the drive electrode 109C. In FIG. 11 , the drive electrode 109C is arranged so as to overlap the switching element 134C. This configuration prevents the switching element 134C from being affected by radio waves. The switching element 134C is driven by a drive circuit 600C (see FIG. 1 ). The orientation of the liquid crystal molecules 116C is controlled according to the driving state of the switching element 134C. As described above, controlling the orientation of the liquid crystal molecules 116C controls the phase of the radio waves reflected by the radio wave reflecting device 100C. This control of the phase of the radio waves controls the traveling direction of the reflected radio waves.

[0077] As described above, in the case of the microwave heating device 10C according to this embodiment, the microwaves emitted from the microwave emission source 300C are blocked or absorbed by the patch electrode 111C, so that it is possible to prevent adverse effects such as heat generation in the switching element 134C caused by irradiation of the microwaves. Therefore, the microwave shielding member 320 shown in FIG. 3 can be omitted.

[0078] [2-2. Driving electrode 109C] Fig. 12 is a plan view showing an outline of a patch electrode of an electromagnetic wave heating device according to one embodiment of the present invention. As shown in Fig. 12, the patch electrode 111C includes a resonating portion 1111C and a connecting portion 1112C.

[0079] The resonator units 1111C are units that resonate with the wavelength of the radio waves emitted from the radio wave emission source 300C, and are arranged in a matrix in the X-axis and Y-axis directions. The sizes of the resonator units 1111C in the X-axis and Y-axis directions are calculated using the wavelength of the radio waves as well as the dielectric constant of the liquid crystal layer 114C, etc. In the case of this embodiment, the frequency of the microwaves emitted from the radio wave emission source 300C is 2.4 GHz, the wavelength is 125 mm, and the sizes of the resonator units 1111C in the X-axis and Y-axis directions are 36 mm.

[0080] The connection portions 1112C connect adjacent resonator portions 1111C in the X-axis direction or the Y-axis direction. The resonator portions 1111C arranged in a matrix are electrically connected by the connection portions 1112C. Therefore, the resonator portions 1111C arranged in a matrix are at the same potential. The connection portions 1112C have their elongated direction in the X-axis direction or the Y-axis direction. The connection portions 1112C connecting adjacent resonator portions 1111C in the X-axis direction have their elongated direction in the X-axis direction. The connection portions 1112C connecting adjacent resonator portions 1111C in the Y-axis direction have their elongated direction in the Y-axis direction.

[0081] The width (width in the Y-axis direction) of the connecting portion 1112C having its elongated side in the X-axis direction is 1 / 100 or less of the size of the resonating portion 1111C in the Y-axis direction. The width (width in the X-axis direction) of the connecting portion 1112C having its elongated side in the Y-axis direction is 1 / 100 or less of the size of the resonating portion 1111C in the X-axis direction. With this configuration, the influence of the connecting portion 1112C on the resonance of the resonating portion 1111C can be reduced.

[0082] As described above, according to the microwave heating device 10C of this embodiment, the microwave reflection device 100C can change the reflection angle of the microwaves emitted from the microwave emission source 300C. Therefore, by adjusting the reflection angle of the microwaves according to the position and size of the object 310C to be heated, the object 310C can be efficiently and uniformly irradiated with microwaves. As a result, the object 310C to be heated can be efficiently and uniformly heated.

[0083] The various configurations of the microwave heating device and reflector unit exemplified as one embodiment of the present invention can be combined as appropriate as long as they are not mutually contradictory. Configurations in which a person skilled in the art appropriately adds or deletes components or modifies the design, or adds or omits processes or modifies conditions, based on the microwave heating device and reflector unit disclosed in this specification and drawings, are also included in the scope of the present invention as long as they include the gist of the present invention.

[0084] Even if there are other effects and advantages different from those brought about by the aspects of the embodiments disclosed in this specification, if they are clear from the description in this specification or can be easily predicted by a person skilled in the art, they are naturally understood to be brought about by the present invention.

[0085] 10: microwave heating device, 100: microwave reflecting device, 102: reflector unit cell, 102a: first reflector unit cell, 102b: second reflector unit cell, 104: dielectric substrate, 106: opposing substrate, 108: patch electrode, 109C: driving electrode, 110: ground electrode, 111C: patch electrode, 112a: first alignment film, 112b: second alignment film, 114: liquid crystal layer, 116: liquid crystal molecules, 118: first wiring, 120: reflector, 122: peripheral region, 124: first driving circuit, 126: terminal portion, 128: sealing material, 130: second driving circuit, 132: second wiring, 134: switching element, 136: undercoat layer, 138: first gate electrode, 140: First gate insulating layer, 142: Semiconductor layer, 144: First connecting wiring, 146: Second gate insulating layer, 148: Second gate electrode, 150: First interlayer insulating layer, 152: Second connecting wiring, 154: Second interlayer insulating layer, 156: Planarization layer, 158: Passivation layer, 160: Printed circuit board (FPC), 162: Radio wave reflecting area, 164: Peripheral area, 200: Heating chamber, 210: Ceiling portion, 220: Side wall portion, 230: Bottom portion, 300: Radio wave emission source, 310: Heating object, 320: Radio wave shielding member, 400: Sensor, 500: Control circuit, 600: Drive circuit, 1111C: Resonating portion, 1112C: Connecting portion, θ1: Incident angle, θ2: Reflection angle

Claims

1. A radio wave irradiation device comprising: a radio wave emission source that emits radio waves; and a radio wave reflection device that is provided on a side wall of a space that stores an object to be heated and reflects the radio waves emitted from the radio wave emission source, wherein the radio wave reflection device includes a plurality of reflection elements arranged in at least one direction, and the reflection elements include a patch electrode, a counter electrode facing the patch electrode, and a liquid crystal layer between the patch electrode and the counter electrode.

2. The radio wave irradiation device according to claim 1, wherein the liquid crystal layer has a thickness of more than 0.5 mm.

3. The radio wave irradiation device according to claim 1, wherein the liquid crystal layer has a thickness of 0.6 mm or more.

4. The radio wave irradiation device according to claim 2 or 3, wherein the radio waves are microwaves.

5. The radio wave irradiation device according to claim 1, wherein the reflection element further includes a switching element connected to the patch electrode.

6. The radio wave irradiation device of claim 5, further comprising a radio wave shielding material that shields the radio waves or a radio wave absorbing material that absorbs the radio waves, wherein the patch electrode is provided at a position close to the radio wave emission source relative to the opposing electrode, the switching element is provided at a position close to the radio wave emission source relative to the patch electrode, and the radio wave shielding material or the radio wave absorbing material is provided at a position close to the radio wave emission source relative to the switching element.

7. The radio wave irradiation device according to claim 1, wherein the reflective element further includes a switching element connected to the counter electrode.

8. The radio wave irradiation device according to claim 7, wherein the patch electrode is provided at a position closer to the radio wave emission source than the counter electrode, and the switching element is provided at a position farther from the radio wave emission source than the counter electrode.

9. A radio wave irradiation device as described in claim 5 or 7, further comprising: a drive circuit for driving the switching element; and a radio wave shielding material for shielding the radio waves or a radio wave absorbing material for absorbing the radio waves, wherein the radio wave reflection device is divided into a radio wave reflection area in which the patch electrodes are arranged and a peripheral area around the radio wave reflection area, the drive circuit is disposed in the peripheral area, and the radio wave shielding material or the radio wave absorbing material is provided in a position closer to the radio wave emission source than the drive circuit.

10. The radio wave irradiation device of claim 5 or 7, further comprising a sensor that detects the position of the object to be heated, a drive circuit that drives the switching element, and a control circuit that controls the drive circuit, wherein the control circuit controls the drive circuit based on position information of the object to be heated detected by the sensor.

11. The radio wave irradiation device according to claim 10, wherein the control circuit controls the drive circuit so that the radio waves reflected by the radio wave reflecting device are directed toward the object to be heated detected by the sensor.

Images