Electro-optic device and display device

Abstract

To provide an electro-optic device in which a passenger's viewing of an image, which you do not want to show the passenger, can be suppressed even when the temperature of a liquid crystal layer is relatively low.SOLUTION: An electro-optic device includes a first control liquid crystal layer 23 existing between a first electrode 24 and a second electrode 25, a temperature sensor 50 that detects the temperature of the first control liquid crystal layer 23, and a second control circuit 60. When a first mode, in which a potential difference between the first electrode 24 and the second electrode 25 is set to zero, is changed to a second mode, in which a potential difference more than zero is generated between the first electrode 24 and the second electrode 25, the second control circuit 60 determines a first potential difference D1 and a second potential difference D2 on the basis of the detecting temperature of the temperature sensor 50, outputs a first start voltage to generate the first potential difference D1 between the first electrode 24 and the second electrode 25, and outputs a first driving voltage to generate the second potential difference D2 between the first electrode 24 and the second electrode 25 at a time point of a first time T1 elapsed after the time point at which the first start voltage is output.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an electro-optical device and a display device.

Background Art

[0002] Patent Document 1 discloses a display system including a liquid crystal layer containing a twisted nematic element (liquid crystal molecules) and having a viewing angle control panel for controlling the viewing angle of a display surface. The display system of Patent Document 1 is mounted on a vehicle, for example. The viewing angle control panel (an example of an electro-optical device) controls the viewing angle of the display area by the operation of liquid crystal molecules. Thereby, a visible state in which an occupant in the driver's seat can view an image and a non-visible state in which the occupant in the driver's seat cannot view the image are switched.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the temperature of the liquid crystal layer is relatively low, the operation time of the liquid crystal molecules becomes relatively slow, and there is a possibility that the switching from the visible state to the non-visible state does not occur early. In this case, there is a possibility that an occupant in the driver's seat views an image that the occupant in the driver's seat does not want to view.

[0005] The present disclosure has been made in view of the above, and an object thereof is to provide an electro-optical device capable of suppressing an occupant from viewing an image that the occupant does not want to view even when the temperature of the liquid crystal layer is relatively low.

Means for Solving the Problems

[0006] The electro-optical device of the present disclosure includes a first substrate having a first electrode, a second substrate having a second electrode facing the first electrode and disposed opposite to the first substrate, a first liquid crystal layer between the first electrode and the second electrode, a temperature sensor for detecting the temperature of the first liquid crystal layer, a first mode in which the potential difference between the first electrode and the second electrode is set to zero, and a control circuit that operates in one of a second mode in which a potential difference greater than zero is generated between the first electrode and the second electrode. The control circuit determines a first potential difference and a second potential difference having a magnitude different from that of the first potential difference based on the detected temperature of the temperature sensor when switching from the first mode to the second mode, outputs a first start voltage that generates the first potential difference between the first electrode and the second electrode, and outputs a first drive voltage that generates the second potential difference between the first electrode and the second electrode after a first time has elapsed since the start of the output of the first start voltage.

[0007] The display device of the present disclosure includes the above electro-optical device and a display panel having a display area, and the electro-optical device overlaps the entire display area in a plan view.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 10

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Figure 12

[0009] Embodiments (embodiments) for implementing the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited by the content described in the following embodiments. In addition, the constituent elements described below include those that can be easily assumed by those skilled in the art and substantially identical ones. Furthermore, the constituent elements described below can be combined as appropriate.

[0010] It should be noted that the disclosure is merely an example, and for those that can be easily conceived by those skilled in the art with appropriate modifications while maintaining the gist of the disclosure, they are naturally included in the scope of the present disclosure. In addition, the drawings are schematically shown in terms of the width, thickness, shape, etc. of each part compared to the actual aspect in order to make the description clearer, but this is merely an example and does not limit the interpretation of the present disclosure. Also, in this specification and each figure, the same reference numerals are given to the same elements as those described above with respect to the already shown figures, and detailed descriptions may be omitted as appropriate.

[0011] The X and Y directions shown in the drawings are orthogonal to each other and correspond to directions parallel to the main surface (e.g., the front surface) of the substrate included in the display device 1. The +X side and -X side in the X direction, and the +Y side and -Y side in the Y direction correspond to the sides of the display device 1. The Z direction corresponds to a direction orthogonal to the main surface of the substrate included in the display device 1. The +Z side in the Z direction corresponds to the front side where an image is displayed on the display device 1, and the -Z side in the Z direction corresponds to the back side of the display device 1. Also, in this specification, "plan view" means looking at the display device 1 along the Z direction from one of the +Z side and -Z side. A plane orthogonal to the Z direction is referred to as the "XY plane". Note that the directions of X, Y, and Z are examples, and the present disclosure is not limited to these directions.

[0012] <First Embodiment> FIG. 1 is a plan view of the display device 1 according to the first embodiment. The display device 1 has a rectangular display area DA for displaying an image on the front surface.

[0013] The display device 1 is mounted on, for example, a vehicle, and the driver M1 in the driver's seat and the passenger M2 in the passenger seat are attached at positions where they can visually recognize the display area DA of the display device 1. Also, the driver M1 in the driver's seat is located on the -X side of the display device 1. The passenger M2 in the passenger seat is located at a position overlapping the display device 1 in the Z direction, specifically, in front of the display device 1. Needless to say, the positions of the passengers M1 and M2 with respect to the display device 1 are not limited to the above positions.

[0014] FIG. 2 is a cross-sectional view of the display device 1 taken along line II-II shown in FIG. 1. The display device 1 includes a display panel 10, a viewing angle control panel 20 which is an electro-optical device, and a backlight unit 30. The display panel 10, the viewing angle control panel 20, and the backlight unit 30 are arranged in this order from the +Z side to the -Z side. Also, the display panel 10 and the viewing angle control panel 20 are bonded together.

[0015] The display panel 10 is a transmissive liquid crystal display of the horizontal electric field type (for example, the FFS (Fringe Field Switching) type). Note that the driving method of the display panel 10 may be the IPS method other than the FFS method, or may be a vertical electric field method such as the TN (Twisted Nematic) method and the VA (Vertical Alignment) method.

[0016] The display panel 10 includes a first display substrate 11, a second display substrate 12 disposed to face the first display substrate 11, and a display liquid crystal layer 13 between the first display substrate 11 and the second display substrate 12.

[0017] The first display substrate 11 is located on the back side of the second display substrate 12. An insulating film IL and an alignment film AL1 are laminated in this order on the front side of the first display substrate 11. The alignment film AL1 is in contact with the display liquid crystal layer 13.

[0018] A common electrode CE is disposed between the first display substrate 11 and the insulating film IL. A plurality of pixel electrodes PE are disposed between the insulating film IL and the alignment film AL1.

[0019] The plurality of pixel electrodes PE overlap the display area DA in a plan view. Also, each of the plurality of pixel electrodes PE overlaps the common electrode CE in a plan view. The pixel electrode PE and the common electrode CE apply a voltage to the display liquid crystal layer 13.

[0020] An alignment film AL2 is disposed on the back side of the second display substrate 12. The alignment film AL2 is in contact with the display liquid crystal layer 13.

[0021] The display panel 10 further has a seal SE1 for sealing liquid crystal molecules in the display liquid crystal layer 13. The display panel 10 further includes a first polarizing plate 14 and a second polarizing plate 15. The first polarizing plate 14 is disposed on the back side of the first display substrate 11. The second polarizing plate 15 is disposed on the front side of the second display substrate 12.

[0022] The front surface of the second polarizing plate 15 corresponds to the front surface of the display device 1. The transmission axis of the first polarizing plate 14 is orthogonal to the Z direction, and the transmission axis of the second polarizing plate 15 is orthogonal to both the Z direction and the transmission axis of the first polarizing plate 14.

[0023] Note that in FIG. 2, only the main part of the display panel 10 is shown in a simplified manner, and the display panel 10 further includes members not shown. For example, the second display substrate 12 includes a light-shielding layer, a color filter layer, an overcoat layer, spacers, and the like. Further, the first display substrate 11 includes a plurality of scanning lines, a plurality of signal lines, a switching element electrically connected to each pixel electrode PE, various insulating films, and the like.

[0024] FIG. 3 is a plan view of the viewing angle control panel 20. The viewing angle control panel 20 overlaps the entire display area DA in a plan view. The viewing angle control panel 20 adjusts the viewing angle in the X direction of the display area DA in the effective area AA. The effective area AA overlaps the display area DA in a plan view.

[0025] The viewing angle is an angle at which the passengers M1 and M2 in the vehicle can view the image displayed in the display area DA. The viewing angle is the viewing angle in the X direction, and as shown in FIG. 2, with the direction (parallel to the Z direction in this embodiment) orthogonal to the main surface (for example, the front surface) of the substrate described later that the viewing angle control panel 20 has as the reference axis Ax, and with an arbitrary point on the display area DA as the reference point, it is represented by the inclination angle in the X direction indicating the inclination to both sides in the X direction from the reference axis Ax.

[0026] In the first embodiment, the viewing angle control panel 20 switches between a first viewing angle θ1 at which both the driver M1 in the driver's seat and the passenger M2 in the passenger seat can view the image displayed in the display area DA, and a second viewing angle θ2 at which the driver M1 in the driver's seat cannot view the image and the passenger M2 in the passenger seat can recognize the image (details will be described later).

[0027] The viewing angle control panel 20 is a vertical electric field mode (e.g., TN mode) liquid crystal panel. As shown in FIG. 2, the viewing angle control panel 20 includes a first control substrate 21, a second control substrate 22 disposed opposite to the first control substrate 21, and a first control liquid crystal layer 23 between the first control substrate 21 and the second control substrate 22.

[0028] The first control substrate 21 is located on the back side of the second control substrate 22. On the front side of the first control substrate 21, an alignment film AL3 and a first electrode 24 are disposed. The alignment film AL3 is in contact with the first control liquid crystal layer 23. The first electrode 24 is in a single sheet form and is disposed between the first control substrate 21 and the alignment film AL3. The first electrode 24 overlaps with the effective area AA in plan view.

[0029] On the back side of the second control substrate 22, an alignment film AL4 and a second electrode 25 are disposed. The alignment film AL4 is in contact with the first control liquid crystal layer 23.

[0030] The second electrode 25 is disposed between the second control substrate 22 and the alignment film AL4. The second electrode 25 is disposed opposite to the first electrode 24. The second electrode 25 overlaps with the effective area AA in plan view.

[0031] Note that the first display substrate 11, the second display substrate 12, the first control substrate 21, and the second control substrate 22 are made of, for example, glass and resin and have light transmittance. The common electrode CE, the pixel electrode PE, the first electrode 24, and the second electrode 25 are made of a conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) and have light transmittance. The alignment films AL1, AL2, AL3, AL4 are horizontal alignment films having an alignment regulating force parallel to the XY plane.

[0032] The viewing angle control panel 20 further has a seal SE2 for sealing liquid crystal molecules in the first control liquid crystal layer 23. As will be described later, the first control liquid crystal layer 23 has a rotation ability to rotate the polarization axis of a polarization component that is linearly polarized light.

[0033] In addition, the viewing angle control panel 20 further includes a third polarizing plate 27, a fourth polarizing plate 28, and a polarization axis rotation element 29. The third polarizing plate 27 is disposed on the back side of the first control substrate 21. The fourth polarizing plate 28 is disposed on the front side of the second control substrate 22. The polarization axis rotation element 29 is disposed on the front side of the fourth polarizing plate 28.

[0034] The transmission axis of the third polarizing plate 27 is orthogonal to the Z direction. The transmission axis of the fourth polarizing plate 28 is orthogonal to the Z direction and the transmission axis of the third polarizing plate 27, respectively. Further, the transmission axis of the fourth polarizing plate 28 and the transmission axis of the first polarizing plate 14 are located in different orientations from each other about the Z axis along the Z direction.

[0035] The polarization axis rotation element 29 is an optical sheet that rotates the polarization axis of the light traveling from the fourth polarizing plate 28 toward the display panel 10. The light transmitted through the fourth polarizing plate 28 has a polarization axis parallel to the transmission axis of the fourth polarizing plate 28. The polarization axis rotation element 29 rotates the polarization axis of the light transmitted through the fourth polarizing plate 28 so as to align it with the transmission axis of the first polarizing plate 14.

[0036] Note that the polarization axis rotation element 29 may be a single optical sheet or a multilayer optical sheet. Further, the polarization axis rotation element 29 may be any element that can exhibit the function of rotating the polarization axis, and is not limited to an optical sheet, and may be an element having optical rotation ability such as a twisted nematic liquid crystal element.

[0037] The backlight unit 30 irradiates light to the display panel 10 through the viewing angle control panel 20. The backlight unit 30 is an edge type and includes a light source (not shown) and a light guide plate (not shown). The light source is, for example, an LED (Light Emitting Diode) or a fluorescent lamp. The light guide plate guides the light emitted from the light source to irradiate the viewing angle control panel 20. Note that the backlight unit 30 may be a direct - type.

[0038] Note that the display device 1 does not necessarily include the backlight unit 30. In this case, the display device 1 is configured such that natural light illuminates the display panel 10.

[0039] In such a display device 1, the light emitted from the backlight unit 30 passes through the viewing angle control panel 20 and further through the display panel 10, so that an image is output to the display area DA.

[0040] Next, the operation of the viewing angle control panel 20 for adjusting the viewing angle of the display area DA will be described. The driving method of the viewing angle control panel 20 is the TN method as described above. Also, the liquid crystal molecules included in the first control liquid crystal layer 23 are in a twisted alignment state.

[0041] First, a state where no voltage is applied to the first control liquid crystal layer 23 will be described. In a state where no voltage is applied to the first control liquid crystal layer 23, the orientation of the liquid crystal molecules included in the first control liquid crystal layer 23 is regulated in the initial orientation direction by the alignment films AL3 and AL4. The major axis of the liquid crystal molecules in the initial orientation direction is orthogonal to the Z direction and parallel to the XY plane.

[0042] Thereby, in the first control liquid crystal layer 23, the direction of light propagation does not change. The light that has passed through the viewing angle control panel 20 passes through the display panel 10. Let the viewing angle of the display area DA in a state where no voltage is applied to the first control liquid crystal layer 23 be the first viewing angle θ1. When the viewing angle of the display area DA is the first viewing angle θ1, both passengers M1 and M2 can visually recognize the image of the display area DA.

[0043] On the other hand, in a state where a voltage is applied to the first control liquid crystal layer 23, the major axis of the liquid crystal molecules included in the first control liquid crystal layer 23 is not orthogonal to the Z direction and is inclined with respect to the XY plane. Also, the lower the temperature of the first control liquid crystal layer 23, the slower the rotation speed (response speed) of the major axis of the liquid crystal molecules with respect to the initial orientation direction.

[0044] By the long axis of the liquid crystal molecules being inclined (rotated), in the first control liquid crystal layer 23, light is refracted according to the inclination of the long axis of the liquid crystal molecules. The light refracted by the viewing angle control panel 20 passes through the display panel 10. As a result, the viewing angle of the display area DA becomes the second viewing angle θ2 (details will be described later). The second viewing angle θ2 is smaller than the first viewing angle θ1. When the viewing angle of the display area DA becomes the second viewing angle θ2, the passenger M2 located in front of the display device 1 can visually recognize the image displayed in the display area DA, but the passenger M1 in the driver's seat located on the -X side of the display device 1 has difficulty visually recognizing the image displayed in the display area DA.

[0045] In this way, the viewing angle of the display area DA is switched by the voltage applied to the first control liquid crystal layer 23 in the viewing angle control panel 20.

[0046] The display device 1 further includes a first control circuit 40, a temperature sensor 50, and a second control circuit 60.

[0047] The first control circuit 40 is disposed on the first display substrate 11. The first control circuit 40 controls the voltage applied to the display liquid crystal layer 13 based on the pixel signals transmitted from an external device (not shown), and modulates the polarization component of the light passing through the display liquid crystal layer 13, thereby displaying an image in the display area DA.

[0048] The temperature sensor 50 is disposed on the first control substrate 21. The temperature sensor 50 detects the temperature of the first control liquid crystal layer 23. Specifically, the temperature sensor 50 detects the temperature of the first control liquid crystal layer 23 through the alignment film AL3, the first electrode 24, and the first control substrate 21. The detected temperature by the temperature sensor 50 is output to the second control circuit 60.

[0049] The second control circuit 60 is disposed on the first control substrate 21. The second control circuit 60 controls the viewing angle control panel 20 based on the switching signal transmitted from an external device. The second control circuit 60 switches the viewing angle of the display area DA as described above by controlling the voltage applied to the first control liquid crystal layer 23.

[0050] The switching signal includes a visual recognition signal for enabling both the driver M1 in the driver's seat and the passenger M2 in the passenger seat to visually recognize the image displayed in the display area DA, and a non-visual recognition signal for preventing the driver M1 in the driver's seat from visually recognizing the image displayed in the display area DA and enabling the passenger M2 in the passenger seat to visually recognize the image.

[0051] For example, when a video is being displayed in the display area DA and the passenger M2 in the passenger seat does not want the driver M1 in the driver's seat to visually recognize the video while driving, the passenger M2 in the passenger seat turns on a switch (not shown) in an external device, and the non-visual recognition signal is transmitted to the second control circuit 60.

[0052] When the second control circuit 60 receives the visual recognition signal, it controls the viewing angle control panel 20 in a visual recognition mode in which the image displayed in the display area DA is visually recognized by both the driver M1 in the driver's seat and the passenger M2 in the passenger seat.

[0053] In the visual recognition mode, the second control circuit 60 sets the potential difference between the first electrode 24 and the second electrode 25 of the viewing angle control panel 20 to zero. That is, the second control circuit 60 does not apply a voltage between the first electrode 24 and the second electrode 25. As a result, no voltage is applied to the first control liquid crystal layer 23, and as described above, the viewing angle of the display area DA is the first viewing angle θ1, and both the driver M1 in the driver's seat and the passenger M2 in the passenger seat can visually recognize the image displayed in the display area DA.

[0054] On the other hand, when the second control circuit 60 receives the non-visual recognition signal, it controls the viewing angle control panel 20 in a non-visual recognition mode in which the image displayed in the display area DA is not visually recognized by the driver M1 in the driver's seat and is visually recognized by the passenger M2 in the passenger seat. In the non-visual recognition mode, the second control circuit 60 outputs a voltage that generates a potential difference greater than zero between the first electrode 24 and the second electrode 25 of the viewing angle control panel 20, and sets the viewing angle of the display area DA to the second viewing angle θ2.

[0055] As described above, the lower the temperature of the first control liquid crystal layer 23, the slower the response speed of the liquid crystal molecules. Therefore, the lower the temperature of the first control liquid crystal layer 23, the longer it takes for the viewing angle of the display area DA to switch, and there is a possibility that the occupant M1 of the driver's seat may view an image that the occupant M1 of the driver's seat does not want to view. Therefore, in order to quickly switch the viewing angle of the display area DA, the second control circuit 60 adjusts the potential difference between the first electrode 24 and the second electrode 25 as described below.

[0056] FIG. 4 is a flowchart executed by the second control circuit 60 when switching from the viewing mode to the non-viewing mode. When the second control circuit 60 is operating in the viewing mode and receives a non-viewing signal, it switches from the viewing mode to the non-viewing mode and executes the flowchart of FIG. 4.

[0057] In step S1, the second control circuit 60 determines the first potential difference D1 and the second potential difference D2 based on the detected temperature of the temperature sensor 50.

[0058] FIG. 5 is a diagram showing a first correlation between the first potential difference D1 and the second potential difference D2 and the detected temperature of the temperature sensor 50. The vertical axis of FIG. 5 is the potential difference. The horizontal axis of FIG. 5 is the detected temperature of the temperature sensor 50, which corresponds to the temperature of the first control liquid crystal layer 23.

[0059] The lower the detected temperature of the temperature sensor 50, the greater the magnitude of the first potential difference D1. Also, the lower the detected temperature of the temperature sensor 50, the greater the magnitude of the second potential difference D2. At any detected temperature of the temperature sensor 50, the magnitudes of the first potential difference D1 and the second potential difference D2 are different from each other. Specifically, at any detected temperature of the temperature sensor 50, the magnitude of the first potential difference D1 is greater than the magnitude of the second potential difference D2. Also, the second potential difference D2 is the potential difference corresponding to the second viewing angle θ2. The first correlation is derived in advance by experiments, simulations, etc. and is stored in the second control circuit 60 in advance.

[0060] Subsequently, in step S2 shown in FIG. 4, the second control circuit 60 outputs a first start voltage that generates a first potential difference D1 between the first electrode 24 and the second electrode 25.

[0061] Furthermore, in step S3, the second control circuit 60 determines whether or not a first time T1 has elapsed since the first start voltage was output. The first time T1 is the time during which the first start voltage is output, and is derived in advance by experiments, simulations, etc., and is stored in the second control circuit 60 in advance. If the first time T1 has not elapsed (NO in step S3), the second control circuit 60 repeatedly executes step S3 and continues to output the first start voltage.

[0062] On the other hand, when the first time T1 has elapsed (YES in step S3), in step S4, the second control circuit 60 outputs a first intermediate voltage between the first electrode 24 and the second electrode 25. The first intermediate voltage is a voltage in which the potential difference between the first electrode 24 and the second electrode 25 gradually changes from the first potential difference D1 to the second potential difference D2.

[0063] Subsequently, in step S5, the second control circuit 60 determines whether or not a second time T2 has elapsed since the first intermediate voltage was output. The second time T2 is the time during which the first intermediate voltage is output, and is derived in advance by experiments, simulations, etc., and is stored in the second control circuit 60 in advance. In the present first embodiment, the second time T2 is shorter than the first time T1. Note that the second time T2 may be equal to the first time T1, or may be longer than the first time T1. If the second time T2 has not elapsed (NO in step S5), the second control circuit 60 repeatedly executes step S5.

[0064] On the other hand, when the second time T2 has elapsed (YES in step S5), in step S6, the second control circuit 60 outputs a first drive voltage that generates a second potential difference D2 between the first electrode 24 and the second electrode 25. That is, the second control circuit 60 outputs the first intermediate voltage from the time when the first time T1 has elapsed until the time when the second time T2 has elapsed, and outputs the first drive voltage from the time when the second time T2 has elapsed.

[0065] Subsequently, in step S7, the second control circuit 60 determines whether a visual recognition signal has been received. If the visual recognition signal has not been received (NO in step S7), the second control circuit 60 repeats step S7 and continues to output the first drive voltage.

[0066] On the other hand, when the second control circuit 60 receives the visual recognition signal (YES in step S7), in step S8, it stops outputting the first drive voltage and ends the program. That is, when the second control circuit 60 receives the visual recognition signal in the non-visual recognition mode, it switches to the visual recognition mode and does not apply a voltage between the first electrode 24 and the second electrode 25.

[0067] Note that the second control circuit 60 uses one of the first electrode 24 and the second electrode 25 as a common electrode, and executes a method (so-called common inversion method) of inverting the polarity of the common electrode, for example, every one frame.

[0068] FIG. 6 is a time chart showing the operation of the viewing angle control panel 20 when the second control circuit 60 executes the flowchart shown in FIG. 4.

[0069] When the second control circuit 60 is operating in the visual recognition mode and a non-visual recognition signal is output from a state where the viewing angle of the display area DA is the first viewing angle θ1, the second control circuit 60 switches to the non-visual recognition mode as described above. As a result, the first start voltage is output and a first potential difference D1 is generated between the first electrode 24 and the second electrode 25 (time t1: step S2), and the liquid crystal molecules of the first control liquid crystal layer 23 begin to tilt from a state where the major axis is orthogonal to the Z direction. Thereby, the viewing angle of the display area DA begins to decrease from the first viewing angle θ1.

[0070] When the first intermediate voltage starts to be output at the time (time t3) when the second time T2 has elapsed since the start of the output of the first intermediate voltage, the output of the first intermediate voltage stops. At the time (time t3) when the second time T2 has elapsed, the potential difference between the first electrode 24 and the second electrode 25 becomes the second potential difference D2.

[0071] When the first intermediate voltage starts to be output at the time (time t3) when the second time T2 has elapsed since the start of the output of the first intermediate voltage, the output of the first intermediate voltage stops. At the time (time t3) when the second time T2 has elapsed, the potential difference between the first electrode 24 and the second electrode 25 becomes the second potential difference D2.

[0072] Then, from the time (time t3) when the second time T2 has elapsed, the first driving voltage is output (step S6), and the potential difference between the first electrode 24 and the second electrode 25 is maintained at the second potential difference D2. As a result, the viewing angle of the display area DA becomes the second viewing angle θ2. While the first driving voltage is being output, the inclination of the liquid crystal molecules is maintained, and the viewing angle of the display area DA is maintained at the second viewing angle θ2.

[0073] Then, when a visual recognition signal is output and the output of the first driving voltage stops (time t4: step S8), the liquid crystal molecules tilt and return to a state where the major axis is orthogonal to the Z direction. As a result, the viewing angle of the display area DA returns to the first viewing angle θ1.

[0074] Next, the differences from the above-described display device 1 will be mainly described for a comparative example of the display device 1 of the first embodiment. In a display device (not shown) of the comparative example, when the second control circuit 60 receives a non-visual recognition signal and switches from the visual recognition mode to the non-visual recognition mode, the first driving voltage is output without outputting the first start voltage and the first intermediate voltage. In the display device of the comparative example, when the first driving voltage is output, the liquid crystal molecules of the first controlled liquid crystal layer 23 start to tilt from a state where the major axis is orthogonal to the Z direction and stop at an inclination angle corresponding to the second viewing angle θ2.

[0075] As described above, the second potential difference D2 of the first driving voltage is smaller than the first potential difference D1 of the first start voltage output by the display device 1 of the present first embodiment. Therefore, the response speed of the liquid crystal molecules in the display device of the comparative example is slower than that of the liquid crystal molecules in the display device 1 of the present first embodiment. Therefore, regarding the time taken to switch from the first viewing angle θ1 to the second viewing angle θ2, the display device of the comparative example is slower than the display device 1 of the present first embodiment.

[0076] That is, in the display device 1 of the present first embodiment, when a non-visibility signal is output and the operation mode of the second control circuit 60 is switched from the visibility mode to the non-visibility mode, as described above, the first start voltage, the first intermediate voltage, and the first driving voltage are output in this order, so that the response speed of the liquid crystal molecules can be increased compared to the display device of the comparative example. Therefore, the viewing angle of the display area DA can be quickly switched from the first viewing angle θ1 to the second viewing angle θ2.

[0077] Also, as described above, the lower the detected temperature of the temperature sensor 50 (the temperature of the first control liquid crystal layer 23), the larger the magnitude of the first potential difference D1 corresponding to the first start voltage. The larger the magnitude of the first potential difference D1, the greater the response speed of the liquid crystal molecules. Therefore, in the display device 1 of the present first embodiment, even when the temperature of the first control liquid crystal layer 23 is relatively low, the viewing angle of the display area DA can be quickly switched from the first viewing angle θ1 to the second viewing angle θ2. Therefore, it is possible to prevent the passenger M1 from viewing an image that the passenger M1 does not want to view.

[0078] <Modification Example of the First Embodiment> Next, the display device 1 according to the modification example of the first embodiment of the present disclosure will be mainly described with differences from the display device 1 according to the above first embodiment.

[0079] In the display device 1 of the first embodiment described above, the second control circuit 60 may output the first driving voltage from the time when the first period T1 has elapsed (time t2: see FIG. 6) without outputting the first intermediate voltage. That is, in the flowchart shown in FIG. 4, when the first period T1 has elapsed (YES in step S3), the second control circuit 60 does not execute steps S4 and S5, but executes step S6 to output the first driving voltage. That is, the second control circuit 60 outputs a first driving voltage that generates a second potential difference D2 between the first electrode 24 and the second electrode 25 after the first period T1 has elapsed from the time when the output of the first start voltage is started.

[0080] Also, in the display device 1 of the first embodiment described above, steps S2 and S3 shown in FIG. 4 do not have to be executed. In this case, when the second control circuit 60 determines the first potential difference D1 and the second potential difference D2 in step S1, it outputs the first intermediate voltage in step S4 without outputting the first start voltage.

[0081] Also, in the display device 1 of the first embodiment described above, the first potential difference D1 may be a predetermined value determined in advance regardless of the detected temperature of the temperature sensor 50. Further, in this case, the second control circuit 60 may determine the first period T1 and the second period T2 based on the detected temperature of the temperature sensor 50 in step S1 shown in FIG. 4.

[0082] FIG. 7 is a diagram showing a second correlation relationship between the detected temperature of the temperature sensor 50, the first period T1, and the second period T2 in the display device 1 according to a modification of the first embodiment of the present disclosure.

[0083] The lower the detected temperature of the temperature sensor 50, the longer the first time T1. Also, the lower the detected temperature of the temperature sensor 50, the longer the second time T2. At any detected temperature of the temperature sensor 50, the first time T1 and the second time T2 are different from each other. Specifically, at any detected temperature of the temperature sensor 50, the first time T1 is longer than the second time T2. The second correlation is derived in advance by experiments, simulations, etc., and is stored in the second control circuit 60 in advance. Note that in this modification, at any detected temperature of the temperature sensor 50, the first time T1 may be equal to the second time T2, or may be shorter than the second time T2.

[0084] Also, in the display device 1 of the first embodiment described above, when the detected temperature of the temperature sensor 50 is equal to or lower than room temperature (temperature within the range of 5°C or higher and 35°C or lower), the magnitude of the first potential difference D1 is determined to be larger than the magnitude of the second potential difference D2 as described above. When the detected temperature of the temperature sensor 50 is higher than room temperature, the magnitude of the first potential difference D1 may be determined to be smaller than the magnitude of the second potential difference D2. In this case, over the entire operating temperature range of the display device 1, the time for the viewing angle of the display area DA to switch from the first viewing angle θ1 to the second viewing angle θ2 can be made constant.

[0085] Also, in the display device 1 of the first embodiment described above, when the detected temperature of the temperature sensor 50 is lower than room temperature, the magnitude of the first potential difference D1 is determined to be larger than the magnitude of the second potential difference D2 as described above. When the detected temperature of the temperature sensor 50 is equal to or higher than room temperature, the magnitude of the first potential difference D1 may be determined to be smaller than the magnitude of the second potential difference D2. In this case, over the entire operating temperature range of the display device 1, the time for the viewing angle of the display area DA to switch from the first viewing angle θ1 to the second viewing angle θ2 can be made constant in a relatively slow state.

[0086] <Second Embodiment> Next, the display device 1 according to the second embodiment of the present disclosure will be mainly described with differences from the display device 1 according to the first embodiment described above.

[0087] FIG. 8 is a cross-sectional view of the viewing angle control panel 120 in the display device 1 according to the second embodiment of the present disclosure. The viewing angle control panel 120 of the second embodiment further includes a third control substrate 171, a fourth control substrate 172 disposed opposite to the third control substrate 171, and a second control liquid crystal layer 173 between the third control substrate 171 and the fourth control substrate 172.

[0088] The third control substrate 171 is located on the back side of the fourth control substrate 172. On the front side of the third control substrate 171, an alignment film AL5 and a third electrode 174 are disposed. The alignment film AL5 is in contact with the second control liquid crystal layer 173. The third electrode 174 is in a single sheet form and is disposed between the third control substrate 171 and the alignment film AL5. The third electrode 174 overlaps with the effective region AA in plan view.

[0089] On the back side of the fourth control substrate 172, an alignment film AL6 and a fourth electrode 175 are disposed. The alignment film AL6 is in contact with the second control liquid crystal layer 173. The front side of the fourth control substrate 172 is disposed on the back side of the third polarizing plate 27.

[0090] The fourth electrode 175 is disposed between the fourth control substrate 172 and the alignment film AL6. The fourth electrode 175 is disposed opposite to the third electrode 174. The fourth electrode 175 overlaps with the effective region AA in plan view.

[0091] Note that the third control substrate 171 and the fourth control substrate 172 are made of, for example, glass and resin and have light transmittance. The third electrode 174 and the fourth electrode 175 are made of a conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) and have light transmittance. The alignment films AL5 and AL6 are horizontal alignment films having an alignment regulating force parallel to the XY plane.

[0092] The viewing angle control panel 120 further has a seal SE3 that seals liquid crystal molecules in the second control liquid crystal layer 173. Similar to the first control liquid crystal layer 23, the second control liquid crystal layer 173 has an optical rotation ability to rotate the polarization axis of a linearly polarized light component. Also, the second control liquid crystal layer 173 overlaps the first control liquid crystal layer 23 in plan view. Furthermore, the thickness (i.e., the length in the Z direction) of the first control liquid crystal layer 23 is larger than the thickness of the second control liquid crystal layer 173.

[0093] Also, the viewing angle control panel 120 further includes a fifth polarizing plate 176. The fifth polarizing plate 176 is disposed on the back side of the third control substrate 171. The transmission axis of the fifth polarizing plate 176 is orthogonal to the Z direction and the transmission axis of the third polarizing plate 27, respectively.

[0094] Next, a state where no voltage is applied to the second control liquid crystal layer 173 will be described. In a state where no voltage is applied to the second control liquid crystal layer 173, the major axis of the liquid crystal molecules included in the second control liquid crystal layer 173 is orthogonal to the Z direction. As a result, in the second control liquid crystal layer 173, the direction of light propagation does not change.

[0095] On the other hand, in a state where a voltage is applied to the second control liquid crystal layer 173, the major axis of the liquid crystal molecules included in the second control liquid crystal layer 173 is not orthogonal to the Z direction and is inclined with respect to the XY plane. The lower the temperature of the second control liquid crystal layer 173, the slower the operation of the liquid crystal molecules whose major axis is inclined.

[0096] When the major axis of the liquid crystal molecules is inclined, in the second control liquid crystal layer 173, light is refracted according to the inclination of the major axis of the liquid crystal molecules.

[0097] The light transmitted through the second control liquid crystal layer 173 is incident on the first control liquid crystal layer 23. When a voltage is applied to the second control liquid crystal layer 173, a voltage is also applied to the first control liquid crystal layer 23 as will be described later. Therefore, the light transmitted through the first control liquid crystal layer 23 is refracted according to the inclination of the major axis of the liquid crystal molecules in the first control liquid crystal layer 23.

[0098] That is, when a voltage is applied to the first control liquid crystal layer 23 and the second control liquid crystal layer 173, in the display area DA, the viewing angle of the display area DA becomes small. That is, it becomes difficult for the occupant M1 in the driver's seat to visually recognize the image. Thus, the viewing angle of the display area DA is switched by the voltage applied to the second control liquid crystal layer 173 in the viewing angle control panel 120.

[0099] Also, in the viewing angle control panel 120 of the present second embodiment, light is refracted by the first control liquid crystal layer 23 and the second control liquid crystal layer 173. Therefore, when the viewing angle of the display area DA is the second viewing angle θ2, the inclination angles of the liquid crystal molecules of the first control liquid crystal layer 23 and the liquid crystal molecules of the second control liquid crystal layer 173 can be made smaller than the inclination angle of the liquid crystal molecules of the first control liquid crystal layer 23 in the above-described first embodiment.

[0100] The second control circuit 60 controls the viewing angle control panel 120 based on a switching signal transmitted from an external device, and switches the viewing angle of the display area DA by the voltages applied to the first control liquid crystal layer 23 and the second control liquid crystal layer 173 as described above.

[0101] Specifically, when the second control circuit 60 receives a visual recognition signal, it makes the potential difference between the third electrode 174 and the fourth electrode 175 zero. That is, in the visual recognition mode, the second control circuit 60 does not apply a voltage between the third electrode 174 and the fourth electrode 175. Also, in the visual recognition mode, the second control circuit 60 does not apply a voltage between the first electrode 24 and the second electrode 25, similar to the above-described first embodiment.

[0102] Thereby, in the visual recognition mode, no voltage is applied to each of the first control liquid crystal layer 23 and the second control liquid crystal layer 173. As described above, the viewing angle of the display area DA is the first viewing angle θ1, and both the occupant M1 in the driver's seat and the occupant M2 in the passenger seat can visually recognize the image displayed in the display area DA.

[0103] On the other hand, when the second control circuit 60 receives a non-visual signal, it switches to the non-visual mode, executes the flowchart shown in FIG. 4, and outputs a voltage that generates a potential difference greater than zero between the first electrode 24 and the second electrode 25. As will be described next, it also outputs a voltage that generates a potential difference greater than zero between the third electrode 174 and the fourth electrode 175.

[0104] FIG. 9 is a flowchart executed when the second control circuit 60 of the second embodiment of the present disclosure switches from the visual mode to the non-visual mode. When the second control circuit 60 is operating in the visual mode and receives a non-visual signal, it switches from the visual mode to the non-visual mode and executes the flowchart of FIG. 4 and the flowchart shown in FIG. 9 in parallel.

[0105] In step S11, the second control circuit 60 determines a third potential difference D3 and a fourth potential difference D4 based on the detected temperature of the temperature sensor 50. In the second embodiment, when the potential difference between the first electrode 24 and the second electrode 25 is the second potential difference D2 and the potential difference between the third electrode 174 and the fourth electrode 175 is the fourth potential difference D4, the second potential difference D2 and the fourth potential difference D4 are determined such that the viewing angle of the display area DA becomes the second viewing angle θ2.

[0106] FIG. 10 is a diagram showing a third correlation between the third potential difference D3 and the fourth potential difference D4 and the detected temperature of the temperature sensor 50. The vertical axis of FIG. 10 is the potential difference. The horizontal axis of FIG. 10 is the detected temperature of the temperature sensor 50. The viewing angle control panel 120 is integrated as shown in FIG. 8, and the temperature of the first control liquid crystal layer 23 and the temperature of the second control liquid crystal layer 173 are substantially equal. That is, the detected temperature of the temperature sensor 50 corresponds to the temperature of the second control liquid crystal layer 173. In the second embodiment, the temperature sensor 50 may be disposed on the third control substrate 171.

[0107] The lower the detected temperature of the temperature sensor 50, the greater the magnitude of the third potential difference D3. Also, the lower the detected temperature of the temperature sensor 50, the greater the magnitude of the fourth potential difference D4. At any detected temperature of the temperature sensor 50, the magnitude of the third potential difference D3 is different from the magnitude of the fourth potential difference D4. Specifically, at any detected temperature of the temperature sensor 50, the magnitude of the third potential difference D3 is greater than the magnitude of the fourth potential difference D4.

[0108] Furthermore, at any detected temperature of the temperature sensor 50, the magnitude of the third potential difference D3 is smaller than the magnitude of the first potential difference D1. Also, at any detected temperature of the temperature sensor 50, the magnitude of the fourth potential difference D4 is smaller than the magnitude of the second potential difference D2. The third correlation relationship is derived in advance by experiments, simulations, etc., and is stored in the second control circuit 60 in advance.

[0109] Subsequently, in step S12 shown in FIG. 9, the second control circuit 60 outputs a second start voltage that generates a third potential difference D3 between the third electrode 174 and the fourth electrode 175.

[0110] Furthermore, in step S13, the second control circuit 60 determines whether or not a third time T3 has elapsed since the second start voltage was output. The third time T3 is the time when the second start voltage is output, is derived in advance by experiments, simulations, etc., and is stored in the second control circuit 60 in advance. In the present second embodiment, the third time T3 is shorter than the first time T1. Note that the third time T3 may be equal to the first time T1, or may be longer than the first time T1. If the third time T3 has not elapsed (NO in step S13), the second control circuit 60 repeatedly executes step S13 and continues to output the second start voltage.

[0111] On the other hand, when the third time T3 has elapsed (YES in step S13), the second control circuit 60 outputs a second intermediate voltage between the third electrode 174 and the fourth electrode 175 in step S14. The second intermediate voltage is a voltage in which the potential difference between the third electrode 174 and the fourth electrode 175 gradually changes from the third potential difference D3 to the fourth potential difference D4.

[0112] Subsequently, in step S15, the second control circuit 60 determines whether or not a fourth time T4 has elapsed since the second intermediate voltage was output. The fourth time T4 is the time during which the second intermediate voltage is output, and is derived in advance by experiments, simulations, etc., and is stored in the second control circuit 60 in advance.

[0113] In this second embodiment, the fourth time T4 is shorter than the second time T2. Also, the sum of the third time T3 and the fourth time T4 is determined such that the time until the tilt angle of the liquid crystal molecules in the second control liquid crystal layer 173 becomes the angle corresponding to the second viewing angle θ2 is equal to the time until the tilt angle of the liquid crystal molecules in the first control liquid crystal layer 23 becomes the angle corresponding to the second viewing angle θ2. In this second embodiment, the sum of the third time T3 and the fourth time T4 is equal to the sum of the first time T1 and the second time T2. Note that the sum of the third time T3 and the fourth time T4 may be different from the sum of the first time T1 and the second time T2.

[0114] If the fourth time T4 has not elapsed (NO in step S15), the second control circuit 60 repeatedly executes step S15.

[0115] On the other hand, if the fourth time T4 has elapsed (YES in step S15), the second control circuit 60 outputs a second driving voltage that generates a fourth potential difference D4 between the third electrode 174 and the fourth electrode 175 in step S16. That is, the second control circuit 60 outputs the second intermediate voltage from the time when the third time T3 has elapsed until the time when the fourth time T4 has elapsed, and outputs the second driving voltage from the time when the fourth time T4 has elapsed.

[0116] Subsequently, the second control circuit 60 determines whether or not a visual recognition signal has been received in step S17. If the visual recognition signal has not been received (NO in step S17), the second control circuit 60 repeatedly executes step S17 and continues to output the second driving voltage.

[0117] On the other hand, when the second control circuit 60 receives a visual recognition signal (YES in step S17), it stops outputting the second drive voltage in step S18 and ends the program. In this way, when the second control circuit 60 is in the non-visual recognition mode and receives a visual recognition signal, it ends the program shown in FIGS. 4 and 9. As a result, the second control circuit 60 switches to the visual recognition mode and does not apply a voltage between the first electrode 24 and the second electrode 25, and between the third electrode 174 and the fourth electrode 175.

[0118] Note that the second control circuit 60 executes a method (so-called common inversion method) in which one of the third electrode 174 and the fourth electrode 175 is used as a common electrode and the polarity of the common electrode is inverted, for example, every one frame.

[0119] FIG. 11 is a time chart showing the operation of the viewing angle control panel 120 when the second control circuit 60 executes the flowchart shown in FIG. 9. Note that when the second control circuit 60 executes the flowchart shown in FIG. 9, it also executes the flowchart shown in FIG. 4 in parallel as described above, and the potential difference between the first electrode 24 and the second electrode 25 changes in the same manner as the time chart shown in FIG. 6. Hereinafter, the potential difference between the third electrode 174 and the fourth electrode 175 will be mainly described.

[0120] When the second control circuit 60 is operating in the visual recognition mode and a non-visual recognition signal is output from a state where the viewing angle of the display area DA is the first viewing angle θ1, the second control circuit 60 switches to the non-visual recognition mode as described above. As a result, a third potential difference D3 is generated between the third electrode 174 and the fourth electrode 175, and the second start voltage (time t1: step S12), and the liquid crystal molecules of the second control liquid crystal layer 173 begin to tilt. As a result, the viewing angle of the display area DA begins to decrease from the first viewing angle θ1.

[0121] When the third hour T3 has elapsed since the time when the second start voltage was output (time t12), the output of the second start voltage stops and the second intermediate voltage is output (step S14). When the second intermediate voltage is being output, the potential difference between the third electrode 174 and the fourth electrode 175 gradually decreases from the third potential difference D3 to the fourth potential difference D4, and the response speed of the liquid crystal molecules gradually decreases. Therefore, the speed at which the viewing angle of the display area DA decreases gradually decreases.

[0122] When the fourth hour T4 has elapsed since the time when the output of the second intermediate voltage started (time t3), the output of the second intermediate voltage stops. When the fourth hour T4 has elapsed (time t3), the potential difference between the third electrode 174 and the fourth electrode 175 becomes the fourth potential difference D4.

[0123] Then, starting from the time when the fourth hour T4 has elapsed (time t3), the second drive voltage is output (step S16), and the potential difference between the third electrode 174 and the fourth electrode 175 is maintained at the fourth potential difference D4. As a result, the viewing angle of the display area DA becomes the second viewing angle θ2. While the second drive voltage is being output, the tilt of the liquid crystal molecules is maintained, and the viewing angle of the display area DA is maintained at the second viewing angle θ2.

[0124] Then, when a visual recognition signal is output and the output of the second drive voltage stops (time t4: step S18), the liquid crystal molecules tilt and return to a state where the major axis is orthogonal to the Z direction. As a result, the viewing angle of the display area DA returns to the first viewing angle θ1.

[0125] As described above, the thickness of the first control liquid crystal layer 23 is greater than the thickness of the second control liquid crystal layer 173. Therefore, when an electric field generated by the same potential difference acts on each of the first control liquid crystal layer 23 and the second control liquid crystal layer 173, the response speed of the liquid crystal molecules in the first control liquid crystal layer 23 is smaller than the response speed of the liquid crystal molecules in the second control liquid crystal layer 173. Also, as described above, the magnitude of the first potential difference D1 generated by the first start voltage applied to the first control liquid crystal layer 23 is greater than the magnitude of the third potential difference D3 generated by the second start voltage applied to the second control liquid crystal layer 173. Thereby, in the first control liquid crystal layer 23 and the second control liquid crystal layer 173, the timing at which the tilt angle of the liquid crystal molecules corresponding to the first viewing angle θ1 switches to the tilt angle of the liquid crystal molecules corresponding to the second viewing angle θ2 can be made the same. That is, the first potential difference D1, the second potential difference D2, the third potential difference D3, and the fourth potential difference D4 are determined such that the timing at which the tilt angle of the liquid crystal molecules corresponding to the first viewing angle θ1 switches to the tilt angle of the liquid crystal molecules corresponding to the second viewing angle θ2 is the same in the first control liquid crystal layer 23 and the second control liquid crystal layer 173.

[0126] Also, in the present second embodiment, since the viewing angle control panel 120 includes the first control liquid crystal layer 23 and the second control liquid crystal layer 173, as described above, at the second viewing angle θ2, the tilt angles of the liquid crystal molecules of the first control liquid crystal layer 23 and the liquid crystal molecules of the second control liquid crystal layer 173 in the present second embodiment can be made smaller than the tilt angle of the liquid crystal molecules of the first control liquid crystal layer 23 in the above-described first embodiment. Therefore, in the present second embodiment, the sum of the first time T1 and the second time T2 (that is, the sum of the third time T3 and the fourth time T4) can be made shorter than the sum of the first time T1 and the second time T2 in the above-described first embodiment, and the timing of switching from the first viewing angle θ1 to the second viewing angle θ2 can be advanced. Therefore, it is possible to further suppress the passenger M1 from viewing an image that the passenger M1 does not want to view.

[0127] <Modification Example of the Second Embodiment> Next, the display device 1 according to a modification example of the second embodiment of the present disclosure will be mainly described with differences from the display device 1 according to the second embodiment described above.

[0128] In the display device 1 of the second embodiment described above, the third potential difference D3 may be equal to the first potential difference D1. In this case, the first time T1 may be longer than the third time T3, and the sum of the first time T1 and the second time T2 may be longer than the sum of the third time T3 and the fourth time T4.

[0129] Further, the second control circuit 60 may output the second driving voltage from the time when the third time T3 has elapsed without outputting the second intermediate voltage. That is, in the flowchart shown in FIG. 9, when the third time T3 has elapsed (YES in step S13), the second control circuit 60 does not execute steps S14 and S15, but executes step S16 to output the second driving voltage. That is, the second control circuit 60 outputs a second driving voltage that generates a fourth potential difference D4 between the third electrode 174 and the fourth electrode 175 after the third time T3 has elapsed since the output of the second start voltage was started.

[0130] Further, in the display device 1 of the second embodiment described above, steps S12 and S13 shown in FIG. 9 may not be executed. In this case, when the second control circuit 60 determines the third potential difference D3 and the fourth potential difference D4 in step S1, the second control circuit 60 outputs the second intermediate voltage in step S14 without outputting the second start voltage.

[0131] Further, the thickness of the first control liquid crystal layer 23 may be smaller than the thickness of the second control liquid crystal layer 173. In this case, at any detected temperature of the temperature sensor 50, the magnitude of the third potential difference D3 may be smaller than the magnitude of the first potential difference D1, and the magnitude of the fourth potential difference D4 may be smaller than the magnitude of the second potential difference D2.

[0132] Further, in the display device 1 of the second embodiment described above, the third potential difference D3 may be a predetermined value determined in advance regardless of the detected temperature of the temperature sensor 50. Further, in this case, in the display device 1 of the second embodiment described above, the second control circuit 60 may determine the third time T3 and the fourth time T4 based on the detected temperature of the temperature sensor 50 in step S1 shown in FIG. 9.

[0133] FIG. 12 is a diagram showing a fourth correlation relationship between the detected temperature of the temperature sensor 50, the third time T3, and the fourth time T4 in the display device 1 according to a modification of the second embodiment of the present disclosure.

[0134] The smaller the detected temperature of the temperature sensor 50, the longer the third time T3. Also, the smaller the detected temperature of the temperature sensor 50, the longer the fourth time T4. At any detected temperature of the temperature sensor 50, the third time T3 and the fourth time T4 are different from each other. Specifically, at any detected temperature of the temperature sensor 50, the third time T3 is longer than the fourth time T4. The fourth correlation relationship is derived in advance by experiments, simulations, etc., and is stored in the second control circuit 60 in advance. In this modification, at any detected temperature of the temperature sensor 50, the third time T3 may be equal to the fourth time T4, or may be shorter than the fourth time T4.

[0135] Further, in the display device 1 of the second embodiment described above, when the detected temperature of the temperature sensor 50 is at room temperature, the magnitude of the third potential difference D3 is determined to be larger than the magnitude of the fourth potential difference D4 as described above, and when the detected temperature of the temperature sensor 50 is higher than room temperature, the magnitude of the third potential difference D3 may be determined to be smaller than the magnitude of the fourth potential difference D4. In this case, over the entire operating temperature range of the display device 1, the time for switching the viewing angle of the display area DA from the first viewing angle θ1 to the second viewing angle θ2 can be made constant.

[0136] Further, in the display device 1 of the second embodiment described above, when the detected temperature of the temperature sensor 50 is lower than room temperature, the magnitude of the third potential difference D3 is determined to be larger than the magnitude of the fourth potential difference D4 as described above, and when the detected temperature of the temperature sensor 50 is equal to or higher than room temperature, the magnitude of the third potential difference D3 may be determined to be smaller than the magnitude of the fourth potential difference D4. In this case, over the entire operating temperature range of the display device 1, the time for switching the viewing angle of the display area DA from the first viewing angle θ1 to the second viewing angle θ2 can be made constant in a relatively slow state.

[0137] <Other Modifications> The preferred embodiments of the present invention have been described above. However, the present invention is not limited to such embodiments. The content disclosed in the embodiments is merely an example, and various modifications are possible without departing from the spirit of the present invention. Appropriate modifications made without departing from the spirit of the present invention also naturally belong to the technical scope of the present invention. Without departing from the gist of each of the above-described embodiments and each modification example, at least one of various omissions, substitutions, and changes of components can be made.

[0138] For example, the viewing angle control panels 20 and 120 may control the viewing angle in a direction intersecting the X direction.

[0139] In addition, with regard to other operational effects brought about by the aspects described in the present embodiment that are obvious from the description in this specification or can be appropriately conceived by those skilled in the art, they are naturally understood to be brought about by the present disclosure.

[0140] Note that the viewing mode corresponds to the "first mode", and the non-viewing mode corresponds to the "second mode". The viewing angle control panel 20 corresponds to the "electro-optical device". The first control substrate 21 corresponds to the "first substrate", and the second control substrate 22 corresponds to the "second substrate". The third control substrate 171 corresponds to the "third substrate", and the fourth control substrate corresponds to the "fourth substrate". The first control liquid crystal layer 23 corresponds to the "first liquid crystal layer", and the second control liquid crystal layer 173 corresponds to the "second liquid crystal layer". The second control circuit 60 corresponds to the "control circuit". The first intermediate voltage corresponds to the "intermediate voltage".

Explanation of Reference Numerals

[0141] 1 Display device 10 Display panel 20 Viewing angle control panel (electro-optical device) 21 First control substrate (first substrate) 22 Second control substrate (second substrate) 23 First control liquid crystal layer (first liquid crystal layer) 24 First electrode 25 Second electrode 50 Temperature sensor 60 Second control circuit (control circuit) 171 Third control board (third board) 172 Fourth control board (fourth board) 173 Second control liquid crystal layer (second liquid crystal layer) 174 Third electrode 175 Fourth electrode D1 First potential difference D2 Second potential difference D3 Third potential difference D4 Fourth potential difference DA Display area T1 First time T2 Second time T3 Third time T4 Fourth time

Claims

1. A first substrate having a first electrode, a second substrate having a second electrode facing the first electrode and disposed opposite to the first substrate, a first liquid crystal layer between the first electrode and the second electrode, a temperature sensor for detecting the temperature of the first liquid crystal layer, and a control circuit operating in one of a first mode in which the potential difference between the first electrode and the second electrode is set to zero and a second mode in which a potential difference greater than zero is generated between the first electrode and the second electrode. The control circuit is configured such that when switching from the first mode to the second mode, based on the detected temperature of the temperature sensor, a first potential difference and a second potential difference having a magnitude different from that of the first potential difference are determined, a first start voltage for generating the first potential difference between the first electrode and the second electrode is output, and after a first time has elapsed since the output of the first start voltage was started, a first drive voltage for generating the second potential difference between the first electrode and the second electrode is output. An electro-optical device.

2. The magnitude of the first potential difference is greater than the magnitude of the second potential difference. The electro-optical device according to claim 1.

3. The smaller the detected temperature of the temperature sensor, the greater the magnitude of the first potential difference. The electro-optical device according to claim 1.

4. The smaller the detected temperature of the temperature sensor, the longer the first time. The electro-optical device according to claim 1.

5. The control circuit outputs an intermediate voltage in which the potential difference between the first electrode and the second electrode gradually changes from the first potential difference to the second potential difference from the time when the first time has elapsed until a second time having a length different from that of the first time has elapsed, and outputs the first drive voltage from the time when the second time has elapsed. The electro-optical device according to claim 1.

6. The smaller the detected temperature of the temperature sensor, the longer the second time. The electro-optical device according to claim 5.

7. A third substrate having a third electrode, a fourth substrate having a fourth electrode facing the third electrode and disposed opposite to the third substrate, and a second liquid crystal layer between the third electrode and the fourth electrode. Further provided, the first liquid crystal layer overlaps the second liquid crystal layer in plan view, the thickness of the first liquid crystal layer is greater than the thickness of the second liquid crystal layer, and the control circuit when switching from the first mode to the second mode, Determine a third potential difference smaller in magnitude than the first potential difference based on the detected temperature of the temperature sensor, and a fourth potential difference having a magnitude different from that of the third potential difference. Output a second start voltage that causes the third potential difference to occur between the third electrode and the fourth electrode from the time when the output of the first start voltage is started. Output a second drive voltage that causes the fourth potential difference to occur between the third electrode and the fourth electrode after a third time having a length different from that of the first time has elapsed from the time when the output of the second start voltage is started. The electro-optical device according to claim 1.

8. An electro-optical device according to any one of claims 1 to 7, A display panel having a display area, and is provided with: The electro-optical device overlaps the entire display area in plan view. A display device.

Images