Display device

Abstract

To reduce the difference in hue before and after a change in a viewing angle in a display device capable of changing the viewing angle.SOLUTION: A display device 1 comprises: a liquid crystal display panel 10 including a display area DA in which a plurality of pixels P is arranged; a viewing angle control panel 20; and a second control circuit 26. The viewing angle control panel 20 includes a first electrode 24, a second electrode 25 facing the first electrode 24, and a control liquid crystal layer 23 between the first electrode 24 and the second electrode 25. The second control circuit 26 operates the viewing angle control panel 20 in one of a first mode in which a potential difference between the first electrode 24 and the second electrode 25 is set to be zero and a second mode in which the potential difference between the first electrode 24 and the second electrode 25 is set to be larger than zero. In a case where the liquid crystal display panel 10 displays achromatic white in the pixels P, chromaticity of the pixels P when the viewing angle control panel 20 operates in the first mode is equal to chromaticity of the pixels P when the viewing angle control panel 20 operates in the second mode.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a display device. [Background technology]

[0002] Patent Document 1 discloses, as an example of a display device, a display system having a liquid crystal layer including twisted nematic liquid crystal elements (liquid crystal molecules) and a viewing angle control panel that controls the viewing angle of the display surface. The display system of Patent Document 1 is mounted, for example, on a vehicle. The viewing angle control panel (an example of an electro-optical device) controls the viewing angle of the display area by the operation of the liquid crystal molecules. This allows switching between a visible state in which the 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 an image. In both the visible state and the non-visible state of the display system, the occupant in the passenger seat can view an image. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-195388 Summary of the Invention [Problem to be solved by the invention]

[0004] However, due to the behavior of the liquid crystal molecules in the viewing angle control panel between the visible state and the non-visible state, there is a possibility that the color of the image viewed by the passenger in the front passenger seat will differ.

[0005] The present disclosure has been made in view of the above, and aims to suppress the difference in color tone before and after changing the viewing angle in a display device with a changeable viewing angle. [Means for solving the problem]

[0006] The display device of the present disclosure comprises a liquid crystal display panel having a display area in which a plurality of pixels are arranged, an electro-optical device overlapping the liquid crystal display panel in a planar view, and a control circuit, wherein the electro-optical device comprises a first substrate having a first electrode, a second substrate having a second electrode opposite the first electrode, and a liquid crystal layer between the first electrode and the second electrode, and the control circuit operates the electro-optical device in one of a first mode in which the potential difference between the first electrode and the second electrode is zero, and a second mode in which the potential difference between the first electrode and the second electrode is greater than zero, and when the liquid crystal display panel displays achromatic white in the pixel, the chromaticity of the pixel when the electro-optical device operates in the first mode is equal to the chromaticity of the pixel when the electro-optical device operates in the second mode. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view of a display device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a side view of the display device. [Figure 3] FIG. 3 is a diagram showing the circuit configuration of a liquid crystal display panel. [Figure 4] FIG. 4 is a cross-sectional view of the liquid crystal display panel and the viewing angle control panel. [Figure 5] FIG. 5 is a plan view of the viewing angle control panel. [Figure 6] FIG. 6 is a diagram showing the chromaticity of a pixel in the xy chromaticity diagram of the CIE1931 color space. [Figure 7] FIG. 7 is a diagram showing the relationship between the gradation value and brightness of a sub-pixel. [Figure 8] FIG. 8 is a diagram showing the correlation between the grayscale value of a sub-pixel and the voltage applied to the sub-pixel. DETAILED DESCRIPTION OF THE INVENTION

[0008] Modes (embodiments) for carrying out the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially identical. Furthermore, the components described below can be combined as appropriate.

[0009] It should be noted that the disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily conceive of while maintaining the gist of the disclosure are naturally included within the scope of the present disclosure. Furthermore, in order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with respect to the previous drawings may be assigned the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0010] The D1 and D2 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 a substrate included in the display device 1. The +D1 side (the side indicated by the arrow), the -D1 side (the opposite side to the +D1 side) of the D1 direction, and the +D2 side (the side indicated by the arrow) and the -D2 side (the opposite side to the +D2 side) of the D2 direction correspond to sides of the display device 1. The D3 direction corresponds to a direction orthogonal to the main surface of a substrate included in the display device 1, the +D3 side (the side indicated by the arrow) of the D3 direction corresponds to the front side where an image is displayed on the display device 1, and the -D3 side (the opposite side to the +D3 side) of the D3 direction corresponds to the rear side of the display device 1. In addition, in this specification, a "planar view" refers to viewing the display device 1 along the D3 direction from either the +D3 side or the -D3 side. Note that the D1, D2, and D3 directions are merely examples, and the present disclosure is not limited to these directions.

[0011] 1 is a plan view of a display device 1 according to an embodiment of the present disclosure. The display device 1 has, on its front surface, a rectangular display area DA for displaying an image.

[0012] The display device 1 is mounted, for example, in a vehicle, and is attached in a position where a driver's seat passenger M1 and a passenger in the passenger seat M2 can view the display area DA of the display device 1. The driver's seat passenger M1 is positioned on the -D1 side of the display device 1. The passenger in the passenger seat M2 is positioned in a position overlapping the display device 1 in the D3 direction, specifically in front of the display device 1. It goes without saying that the positions of the passengers M1 and M2 relative to the display device 1 are not limited to the above positions.

[0013] 2 is a side view of the display device 1. The display device 1 includes a liquid crystal display panel 10, a viewing angle control panel 20 which is an electro-optical device, and a backlight unit 30. The liquid crystal display panel 10, the viewing angle control panel 20, and the backlight unit 30 are arranged in this order from the +D3 side to the -D3 side. The liquid crystal display panel 10 and the viewing angle control panel 20 are bonded together.

[0014] The liquid crystal display panel 10 is a transmissive liquid crystal display. The liquid crystal display panel 10 may be, for example, an organic EL display or an inorganic EL display. The front surface of the liquid crystal display panel 10 corresponds to the front surface of the display device 1 and has a display area DA. As shown in FIG. 1, the liquid crystal display panel 10 has a plurality of pixels P arranged in a matrix along directions D1 and D2 in the display area DA.

[0015] Each of the multiple pixels P has a first subpixel SP1, a second subpixel SP2, and a third subpixel SP3. The first subpixel SP1 is a red subpixel. The second subpixel SP2 is a green subpixel. The third subpixel SP3 is a blue subpixel. The first subpixel SP1, the second subpixel SP2, and the third subpixel SP3 are arranged in this order along the D1 direction. The arrangement of the first subpixel SP1, the second subpixel SP2, and the third subpixel SP3 is a so-called stripe arrangement. Hereinafter, when the first subpixel SP1, the second subpixel SP2, and the third subpixel SP3 are not to be distinguished from each other, they may be simply referred to as "subpixel SP." It goes without saying that the arrangement of the subpixels SP is not limited to a stripe arrangement, and the number and colors of the subpixels SP are not limited to those described above.

[0016] 3 is a diagram showing the circuit configuration of the liquid crystal display panel 10. The liquid crystal display panel 10 includes a first control circuit 11, and a switching element SW, a subpixel electrode PE, a common electrode CE, a liquid crystal capacitance LC, and a storage capacitance CS, which are included in each of the subpixels SP.

[0017] The first control circuit 11 drives the liquid crystal display panel 10. The first control circuit 11 includes a signal processing circuit 11a, a signal output circuit 11b, and a scanning circuit 11c.

[0018] The signal processing circuit 11a outputs subpixel signals indicating the gradation values ​​of the subpixels SP to the signal output circuit 11b based on an image signal transmitted from an external device. The signal processing circuit 11a also outputs clock signals to the signal output circuit 11b and the scanning circuit 11c, which synchronize the operation of the signal output circuit 11b with the operation of the scanning circuit 11c.

[0019] The signal output circuit 11b outputs subpixel signals to the subpixels SP. The signal output circuit 11b and the subpixels SP are electrically connected via a plurality of signal lines Lb extending along the direction D2.

[0020] The scanning circuit 11c scans the sub-pixels SP in synchronization with the output of the sub-pixel signals by the signal output circuit 11b. The scanning circuit 11c and the sub-pixels SP are electrically connected via a plurality of scanning lines Lc extending along the D1 direction.

[0021] In plan view, an area defined by two signal lines Lb adjacent to each other in the D1 direction and two scanning lines Lc adjacent to each other in the D2 direction corresponds to a sub-pixel SP.

[0022] The switching element SW is configured by, for example, a thin film transistor (TFT). In the switching element SW, the source electrode and the signal line Lb are electrically connected, and the gate electrode and the scanning line Lc are electrically connected.

[0023] The sub-pixel electrode PE is connected to the drain electrode of the switching element SW. A plurality of common electrodes CE are arranged corresponding to the plurality of scanning lines Lc. The sub-pixel electrodes PE and the common electrode CE are light-transmitting.

[0024] The liquid crystal capacitance LC is a capacitance component of the liquid crystal material of the display liquid crystal layer 13, which will be described later, located between the subpixel electrode PE and the common electrode CE. The storage capacitance CS is disposed between an electrode having the same potential as the common electrode CE and an electrode having the same potential as the subpixel electrode PE.

[0025] 4 is a cross-sectional view of the liquid crystal display panel 10 and the viewing angle control panel 20. The liquid crystal display panel 10 further includes a first display substrate 12, a display liquid crystal layer 13, and a second display substrate 14. The first display substrate 12, the display liquid crystal layer 13, and the second display substrate 14 are arranged in this order along the D3 direction from the -D3 side to the +D3 side. The first display substrate 12 and the second display substrate 14 are rectangular in plan view.

[0026] A common electrode CE is arranged on a front surface 12a on the +D3 side of the first display substrate 12. An insulating layer IL is arranged in front of the common electrode CE, and further, a subpixel electrode PE and an alignment film AL1 are arranged.

[0027] The sub-pixel electrode PE is disposed between the insulating layer IL and the alignment film AL1. In this manner, the common electrode CE and the sub-pixel electrode PE are disposed on the first display substrate 12. In other words, the liquid crystal display panel 10 is a lateral electric field liquid crystal display. The driving method of the liquid crystal display panel 10 may be an IPS method other than the FFS method, or a vertical electric field method such as a TN (Twisted Nematic) method or a VA (Vertical Alignment) method.

[0028] The second display substrate 14 is located on the front surface 12a side of the first display substrate 12. A color filter CF, a light-shielding film SM, and an alignment film AL2 are arranged on the back surface of the second display substrate 14. The light-shielding film SM and the color filter CF are arranged between the second display substrate 14 and the alignment film AL2.

[0029] The color filters CF are rectangular in plan view, and one filter is disposed for each subpixel SP. The color filters CF are translucent, and the spectral peak of the light they transmit is predetermined. The spectral peak corresponds to the color of the color filter CF. The color of the color filter CF is the same as the color of the subpixel SP. That is, a red color filter CF is disposed for the first red subpixel SP1, a green color filter CF is disposed for the second green subpixel SP2, and a blue color filter CF is disposed for the third blue subpixel SP3.

[0030] The light-shielding film SM has light-shielding properties and overlaps the boundaries of the sub-pixels SP adjacent to each other in the D1 and D2 directions in a planar view. That is, the light-shielding film SM overlaps the signal lines Lb and the scanning lines Lc in a planar view. Note that the signal lines Lb and the scanning lines Lc are not shown in FIG. 4. The signal lines Lb and the scanning lines Lc are disposed on the front surface 12a of the first display substrate 12.

[0031] The display liquid crystal layer 13 includes a plurality of liquid crystal molecules LM. The display liquid crystal layer 13 is located between the first display substrate 12 and the second display substrate 14, and overlaps with the display area DA in a plan view. Specifically, the display liquid crystal layer 13 is located between two alignment films AL1 and AL2 facing each other.

[0032] As shown in FIG. 4, the liquid crystal display panel 10 further includes a first polarizer 15 disposed on the back surface of the first display substrate 12 and a second polarizer 16 disposed on the front surface of the second display substrate 14.

[0033] The first polarizer 15 has a transmission axis perpendicular to the D3 direction. The second polarizer 16 has a transmission axis perpendicular to the transmission axis of the first polarizer 15 and the D3 direction.

[0034] 5 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 planar view. The viewing angle control panel 20 adjusts the viewing angle of the display area DA in the D1 direction in the effective area AA. The effective area AA overlaps with the display area DA in a planar view.

[0035] The viewing angle is the angle at which passengers M1 and M2 can view the image displayed in the display area DA. The viewing angle is the viewing angle in the D1 direction, and is expressed using a reference axis Ax, which is a direction (parallel to the D3 direction in this embodiment) perpendicular to the main surface (for example, the front surface) of a substrate (described later) of the viewing angle control panel 20 as shown in Fig. 4, and an arbitrary point on the display area DA is used as a reference point, and the tilt angle in the D1 direction represents the tilt from the reference axis Ax to both sides of the D1 direction.

[0036] In this embodiment, the viewing angle control panel 20 switches between a first viewing angle θ1 at which both the driver's seat occupant M1 and the passenger seat occupant M2 can see the image displayed in the display area DA, and a second viewing angle θ2 at which the driver's seat occupant M1 cannot see the image but the passenger seat occupant M2 can recognize the image (details will be described later).

[0037] The viewing angle control panel 20 is a liquid crystal panel of a vertical electric field type (for example, a TN type). The viewing angle control panel 20 includes a first control board 21 (corresponding to the "first board"), a second control board 22 (corresponding to the "second board"), and a control liquid crystal layer 23 (corresponding to the "liquid crystal layer") located between the first control board 21 and the second control board 22. The first control board 21, the control liquid crystal layer 23, and the second control board 22 are arranged in this order from the -D3 side to the +D3 side along the D3 direction.

[0038] The first control substrate 21 is located on the rear side of the second control substrate 22. An alignment film AL3 and a first electrode 24 are arranged on the front side of the first control substrate 21. The alignment film AL3 is in contact with the control liquid crystal layer 23. The first electrode 24 is in the form of a single sheet and is arranged between the first control substrate 21 and the alignment film AL3. The first electrode 24 overlaps with the effective area AA in a plan view.

[0039] An alignment film AL4 and a second electrode 25 are disposed on the rear surface side of the second control substrate 22. The alignment film AL4 is in contact with the control liquid crystal layer .

[0040] The second electrode 25 is disposed between the second control substrate 22 and the alignment film AL4. The second electrode 25 is disposed opposite the first electrode 24. The second electrode 25 overlaps with the effective area AA in a plan view.

[0041] The first display substrate 12, the second display substrate 14, the first control substrate 21, and the second control substrate 22 are made of, for example, glass or resin and are light-transmitting. The common electrode CE, the sub-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 are light-transmitting. The alignment films AL1, AL2, AL3, and AL4 are horizontal alignment films having an alignment regulating force perpendicular to the D3 direction.

[0042] As will be described later, the control liquid crystal layer 23 has an optical rotation power that rotates the polarization axis of a linearly polarized polarized light component. The control liquid crystal layer 23 includes a plurality of liquid crystal molecules LM.

[0043] The viewing angle control panel 20 further includes a third polarizer 27, a fourth polarizer 28, and a polarization axis rotation element 29. The third polarizer 27 is disposed on the rear surface side of the first control board 21. The fourth polarizer 28 is disposed on the front surface side of the second control board 22. The polarization axis rotation element 29 is disposed on the front surface side of the fourth polarizer 28.

[0044] The transmission axis of the third polarizer 27 is perpendicular to the D3 direction. The transmission axis of the fourth polarizer 28 is perpendicular to both the D3 direction and the transmission axis of the third polarizer 27. Furthermore, the transmission axis of the fourth polarizer 28 and the transmission axis of the first polarizer 15 are positioned in different orientations around an axis along the D3 direction.

[0045] The polarization axis rotation element 29 is an optical sheet that rotates the polarization axis of light traveling from the fourth polarizer 28 toward the liquid crystal display panel 10. The light that has passed through the fourth polarizer 28 has a polarization axis that is parallel to the transmission axis of the fourth polarizer 28. The polarization axis rotation element 29 rotates the polarization axis of the light that has passed through the fourth polarizer 28 so that it is aligned with the transmission axis of the first polarizer 15.

[0046] The polarization axis rotation element 29 may be a single optical sheet or a multi-layer optical sheet. The polarization axis rotation element 29 is not limited to an optical sheet as long as it can rotate the polarization axis, and may be an element having optical rotation power such as a twisted nematic liquid crystal element.

[0047] The backlight unit 30 shown in FIG. 2 irradiates the liquid crystal display panel 10 with light via 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 so that it irradiates the viewing angle control panel 20. The backlight unit 30 may also be a direct-type.

[0048] The display device 1 does not necessarily have to include the backlight unit 30. In this case, the display device 1 is configured so that natural light is illuminated onto the liquid crystal display panel 10.

[0049] In such a display device 1, light emitted from the backlight unit 30 passes through the viewing angle control panel 20 and then through the liquid crystal display panel 10. When the first control circuit 11 outputs the subpixel signals to the subpixels SP based on the image signals, an electric field is generated in the display liquid crystal layer 13, changing the orientation of the liquid crystal molecules LM in the display liquid crystal layer 13. This modulates the light passing through the liquid crystal display panel 10, and an image is displayed in the display area DA.

[0050] 5, the viewing angle control panel 20 further includes a second control circuit 26 (corresponding to a "control circuit"). The second control circuit 26 controls the viewing angle control panel 20 in one of two operation modes: a visible mode (corresponding to a "first mode") in which the image displayed in the display area DA is visible to both the occupant M1 in the driver's seat and the occupant M2 in the passenger seat, and a non-visible mode (corresponding to a "second mode") in which the image displayed in the display area DA is not visible to the occupant M1 in the driver's seat but is visible to the occupant M2 in the passenger seat.

[0051] The second control circuit 26 is disposed on the first control board 21. The second control circuit 26 switches between the visible mode and the non-visible mode based on a switching signal transmitted from an external device. The switching signal includes a visible signal that switches the operation mode to the visible mode, and a non-visible signal that switches the operation mode to the non-visible mode.

[0052] For example, when the viewing angle control panel 20 is operating in the viewing mode and a video is displayed in the display area DA, if the passenger M2 in the front passenger seat does not want the driver M1 who is driving to be able to see the video, the passenger M2 in the front passenger seat turns on a switch on an external device, and a non-viewing signal is sent to the second control circuit 26.

[0053] When the second control circuit 26 receives the viewing signal, it controls the viewing angle control panel 20 in the viewing mode. In the viewing mode, the second control circuit 26 sets the potential difference between the first electrode 24 and the second electrode 25 of the viewing angle control panel 20 to zero. In this case, no electric field is generated in the control liquid crystal layer 23, and the long axes of the liquid crystal molecules LM of the control liquid crystal layer 23 are perpendicular to the D3 direction.

[0054] In this case, the direction in which light travels does not change in the control liquid crystal layer 23. The light that has passed through the viewing angle control panel 20 passes through the liquid crystal display panel 10. The viewing angle of the display area DA when the potential difference between the first electrode 24 and the second electrode 25 is zero is defined as 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 view the image in the display area DA.

[0055] On the other hand, when the second control circuit 26 receives a non-viewing signal, it controls the viewing angle control panel 20 in the non-viewing mode. In the non-viewing mode, the second control circuit 26 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. In this case (when the potential difference between the first electrode 24 and the second electrode 25 is greater than zero), an electric field is generated in the control liquid crystal layer 23, and the long axes of the liquid crystal molecules LM of the control liquid crystal layer 23 are not perpendicular to the D3 direction but are tilted with respect to the D3 direction.

[0056] As the long axes of the liquid crystal molecules LM in the control liquid crystal layer 23 are tilted, light is refracted in accordance with the tilt of the long axes of the liquid crystal molecules LM in the control liquid crystal layer 23. The light refracted by the viewing angle control panel 20 is transmitted through the liquid crystal display panel 10. As a result, the viewing angle of the display area DA becomes the second viewing angle θ2.

[0057] 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 positioned in front of the display device 1 can see the image displayed in the display area DA, but the passenger M1 in the driver's seat positioned on the -D1 side of the display device 1 has difficulty seeing the image displayed in the display area DA.

[0058] In this way, the second control circuit 26 switches between the visible mode and the non-visible mode based on a switching signal transmitted from an external device, thereby switching the viewing angle of the display area DA.

[0059] As described above, the occupant M2 views an image in both the visible mode and the non-visible mode. Furthermore, the degree of tilt of the liquid crystal molecules LM of the control liquid crystal layer 23 differs between the visible mode and the non-visible mode, and the amount of light directed toward the occupant M2 differs. Therefore, the color tone of the image viewed by the occupant M2 differs between the visible mode and the non-visible mode. The difference in the color tone of the image may cause the occupant M2 to feel uncomfortable.

[0060] Therefore, the display device 1 reduces the difference in color tone of the image viewed by the passenger M2 between the visible mode and the non-visible mode. Specifically, when the liquid crystal display panel 10 sets the color of the pixel P to achromatic white, the display device 1 equalizes the chromaticity of the pixel P when the viewing angle control panel 20 operates in the visible mode and the chromaticity of the pixel P when the viewing angle control panel 20 operates in the non-visible mode.

[0061] Figure 6 shows the chromaticity of pixel P in the xy chromaticity diagram of the CIE 1931 color space. The chromaticity of pixel P is represented by coordinates on the xy chromaticity diagram of the CIE 1931 color space. CIE stands for the International Commission on Illumination (Commission internationale de l'eclairage in French). Note that the (e) after the comma (') would normally be spelled out, but because it is an environment-dependent character, it is represented in this specification as the letter e. The CIE 1931 color space is a color space defined by the International Commission on Illumination in 1931.

[0062] When the liquid crystal display panel 10 sets the color of the pixel P to achromatic white, the first control circuit 11 sets the gradation values ​​of the first subpixel SP1, second subpixel SP2, and third subpixel SP3 of the pixel P to be equal and maximum. Specifically, when the gradation data indicating the gradation value of the subpixel SP is 8 bits, the gradation value of the subpixel SP is expressed in 256 levels from 0 (zero) to 255. In other words, the gradation values ​​of the first subpixel SP1, second subpixel SP2, and third subpixel SP3 of the pixel P, whose color is achromatic white, are each 255.

[0063] The first white point W1 shown in FIG. 6 indicates the chromaticity of pixel P, which is white in the visible mode. The second white point W2 indicates the chromaticity of pixel P, which is white in the non-visible mode. The chromaticity of pixel P is measured using a colorimeter. The first white point W1 and the second white point W2 are offset from each other in FIG. 6, indicating that the color tone of the image perceived by passenger M2 differs between the visible mode and the non-visible mode. In the example shown in FIG. 6, the second white point W2 is located on the +x side of the first white point W1.

[0064] Point R1 indicates the chromaticity of pixel P when the first subpixel SP1 has a gradation value of 255, the second subpixel SP2 has a gradation value of 0, and the third subpixel SP3 has a gradation value of 0 in the viewing mode. That is, the color of pixel P at point R1 corresponds to the most saturated red in the viewing mode. Point G1 indicates the chromaticity of pixel P when the first subpixel SP1 has a gradation value of 0, the second subpixel SP2 has a gradation value of 255, and the third subpixel SP3 has a gradation value of 0 in the viewing mode. That is, the color of pixel P at point G1 corresponds to the most saturated green in the viewing mode. Point B1 indicates the chromaticity of pixel P when the first subpixel SP1 has a gradation value of 0, the second subpixel SP2 has a gradation value of 0, and the third subpixel SP3 has a gradation value of 255 in the viewing mode. That is, the color of pixel P at point G1 corresponds to the most saturated blue in the viewing mode. In the viewing mode, the color range of pixel P is the range inside the triangle indicated by the solid line with points R1, G1, and B1 as vertices.

[0065] To equalize the chromaticity of the pixel P whose color is white in the visible mode with the chromaticity of the pixel P whose color is white in the non-visible mode, at least one of the luminance of the subpixel SP in the visible mode and the luminance of the subpixel SP in the non-visible mode is adjusted. For simplicity of explanation, the following describes the case where the luminance of the first subpixel SP1 in the non-visible mode is adjusted.

[0066] FIG. 7 is a diagram showing the relationship between the gradation value and brightness of the subpixel SP.

[0067] In the first correlation C1 before the luminance of the subpixel SP is adjusted in the visible mode and the non-visible mode, the luminance when the gradation value is zero is zero, and the luminance when the gradation value is 255 is the first luminance L1.

[0068] To equalize the chromaticity of pixel P whose color is white in the visible mode and the chromaticity of pixel P whose color is white in the non-visible mode, the luminance of red, i.e., the luminance of the first subpixel SP1, is reduced so that the second white point W2 shown in Fig. 6 approaches the first white point W1. In the non-visible mode, when the gradation value of the first subpixel SP1 is 255, the luminance of the first subpixel SP1 is adjusted to the second luminance L2 which is smaller than the first luminance L1 shown in Fig. 7. This makes the chromaticity of pixel P whose color is white in the visible mode and the chromaticity of pixel P whose color is white in the non-visible mode equal.

[0069] The chromaticity of pixel P is indicated by the coordinate (x, y) values ​​on the xy chromaticity diagram shown in FIG. 6. The chromaticity of pixel P can be measured with a photometer. In this specification, the chromaticity of pixel P whose color is white in the visible mode is equal to the chromaticity of pixel P whose color is white in the non-visible mode when the ratio of the x-coordinate value of second white point W2 to the x-coordinate value of first white point W1 and the ratio of the y-coordinate value of second white point W2 to the y-coordinate value of first white point W1 are both 0.99 or more and 1.01 or less. When the ratio of the x-coordinate value and the ratio of the y-coordinate value are both 1, the first white point W1 and the second white point W2 are the same.

[0070] In the non-visible mode, when the luminance of the first subpixel SP1 when the gradation value is 255 is adjusted to a second luminance L2 that is smaller than the first luminance L1, the correlation between the gradation value and luminance of the first subpixel SP1 becomes the second correlation C2 shown in Fig. 7. In the second correlation C2, the luminance when the gradation value is zero is zero, and the luminance when the gradation value is 255 is the second luminance L2.

[0071] Therefore, when the gradation value of the first subpixel SP1 is 255, the second luminance L2 of the first subpixel SP1 in the non-viewing mode is lower than the first luminance L1 of the first subpixel SP1 in the viewing mode. Therefore, when the gradation value of the first subpixel SP1 is the maximum (255) and the gradation values ​​of the second subpixel SP2 and the third subpixel SP3 are zero, the luminance of the pixel P when the viewing angle control panel 20 operates in the viewing mode differs from the luminance of the pixel P when the viewing angle control panel 20 operates in the non-viewing mode.

[0072] Fig. 8 is a diagram showing the correlation between the gradation value of a subpixel SP and the voltage applied to the subpixel SP. The voltage applied to the subpixel SP shown in Fig. 8 corresponds to the voltage of the subpixel signal output by the signal processing circuit 11a. The luminance of the subpixel SP is adjusted by the voltage applied to the subpixel SP.

[0073] The third correlation C3 shown in Fig. 8 corresponds to the first correlation C1 shown in Fig. 7. That is, the first voltage V1 corresponds to the first luminance L1. Moreover, the fourth correlation C4 shown in Fig. 8 corresponds to the second correlation C2 shown in Fig. 7. That is, the second voltage V2 corresponds to the second luminance L2.

[0074] In other words, in the first subpixel SP1, the voltage corresponding to the maximum gradation value (255) when the viewing angle control panel 20 operates in the visible mode is different from the voltage corresponding to the maximum gradation value when the viewing angle control panel 20 operates in the non-visible mode.

[0075] In the above explanation, for simplicity, the luminance of the first subpixel SP1 is adjusted in the non-visible mode to equalize the chromaticity of the pixel P whose color is white in the visible mode with the chromaticity of the pixel P whose color is white in the non-visible mode. However, the luminance of at least one subpixel SP may be adjusted in at least one of the visible mode and the non-visible mode.

[0076] For example, the luminance of at least one subpixel SP may be adjusted in the visible mode. In this case, the first white point W1 shown in FIG. 6 approaches the second white point W2. Alternatively, the luminance of at least one subpixel SP may be adjusted in both the visible mode and the non-visible mode. In this case, both the first white point W1 and the second white point W2 approach chromaticities different from those of the first white point W1 and the second white point W2.

[0077] Therefore, when the gradation value of one of the multiple subpixels SP is maximum and the gradation values ​​of the subpixels SP other than one of the multiple subpixels SP are zero, the luminance of pixel P when the viewing angle control panel 20 operates in the visible mode is different from the luminance of pixel P when the viewing angle control panel 20 operates in the non-visible mode.

[0078] Furthermore, in at least one subpixel SP among the multiple subpixels SP, the voltage corresponding to the maximum gradation value when the viewing angle control panel 20 operates in the visible mode is different from the voltage corresponding to the maximum gradation value when the viewing angle control panel 20 operates in the non-visible mode.

[0079] In this way, by making the chromaticity of pixel P whose color is white in the visible mode equal to the chromaticity of pixel P whose color is white in the non-visible mode, the difference in color tone before and after changing the viewing angle can be suppressed in a display device 1 whose viewing angle is changeable.

[0080] Although preferred embodiments of the present invention have been described above, the present invention is not limited to such embodiments. The contents disclosed in the embodiments are merely examples, 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 naturally fall within the technical scope of the present invention. At least one of various omissions, substitutions, and modifications of components can be made without departing from the spirit of each of the above-described embodiments and modifications.

[0081] For example, the viewing angle control panel 20 may control the viewing angle in a direction intersecting with direction D1.

[0082] The display device 1 may also include two viewing angle control panels 20. In this case, the two viewing angle control panels 20 are arranged to overlap each other in the direction D3.

[0083] The chromaticity of pixel P may also be represented by X, Y, and Z in the CIE XYZ display system. In this case, the X, Y, and Z chromaticity of pixel P may be obtained by a photometer. The CIE X and Z may also be calculated using the CIE Y, x, and y obtained by the photometer and the following equations (1) and (2).

[0084] X = Y × x / y (1) Z = Y × (1 - xy) / y (2)

[0085] 6 may be calculated from the X, Y, and Z values ​​of points R1, G1, and B1. Specifically, in the XYZ display system, if the X, Y, and Z values ​​of point R1 are Xr, Yr, and Zr, the X, Y, and Z values ​​of point G1 are Xg, Yg, and Zg, and the X, Y, and Z values ​​of point B1 are Xb, Yb, and Zb, the coordinates of the first white point W1 are calculated using the following equations (3), (4), (5), (6), and (7).

[0086] Xw=(Xr+Xg+Xb) / 3 (3) Yw=(Yr+Yg+Yb) / 3 (4) Zw=(Zr+Zg+Zb) / 3 (5) xw=Xw / (Xw+Yw+Zw) (6) yw=Yw / (Xw+Yw+Zw) (7)

[0087] In equation (6), xw is the x-coordinate of the first white point W1, and in equation (7), yw is the y-coordinate of the first white point W1. In equations (3), (4), (5), (6), and (7), Xw, Yw, and Zw are the X, Y, and Z coordinates of the first white point W1 in the XYZ display system. The second white point W2 may be calculated in the same way. [Explanation of symbols]

[0088] 1 Display device 10 LCD display panel 20 Viewing angle control panel (electro-optical device) 21 First control board (first board) 22 Second control board (second board) 23 Control liquid crystal layer (liquid crystal layer) 24 1st electrode 25 2nd electrode 26 Second control circuit (control circuit) DA display area P pixel

Claims

1. a liquid crystal display panel having a display area in which a plurality of pixels are arranged; an electro-optical device overlapping the liquid crystal display panel in a plan view; a control circuit; The electro-optical device includes: a first substrate having a first electrode; a second substrate having a second electrode facing the first electrode; a liquid crystal layer between the first electrode and the second electrode; the control circuit operates the electro-optical device in one of a first mode in which a potential difference between the first electrode and the second electrode is zero and a second mode in which a potential difference between the first electrode and the second electrode is greater than zero; When the liquid crystal display panel displays achromatic white in the pixel, the chromaticity of the pixel when the electro-optical device operates in the first mode is equal to the chromaticity of the pixel when the electro-optical device operates in the second mode. Display device.

2. The pixel has a plurality of sub-pixels that are different in color from each other, when the gradation value of one of the plurality of subpixels is maximum and the gradation values ​​of the subpixels other than the one subpixel are zero, the luminance of the pixel when the electro-optical device operates in the first mode is different from the luminance of the pixel when the electro-optical device operates in the second mode; The display device according to claim 1 .

3. The pixel has a plurality of sub-pixels that are different in color from each other, In at least one subpixel among the plurality of subpixels, a voltage corresponding to a maximum grayscale value when the electro-optical device operates in the first mode is different from a voltage corresponding to a maximum grayscale value when the electro-optical device operates in the second mode. The display device according to claim 1 .

4. The chromaticity of the pixel is represented by coordinates on an xy chromaticity diagram of the CIE 1931 color space. The display device according to claim 1 .

Images