JP2009122212A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce thickness, weight and manufacturing cost in a liquid crystal display device which can switch a viewing angle. <P>SOLUTION: A first sub pixel 1A having a wide viewing angle and a second sub pixel having a narrow viewing angle are disposed in pairs in each pixel. In the first sub pixel 1A, alignment of liquid crystal molecules M is controlled by an electric field generated between a first common electrode 14 and first pixel electrodes 16A disposed on a first transparent substrate 10. In the second sub pixel 1B, alignment of the liquid crystal molecules M is controlled by an electric field generated between the first common electrode 14 and second pixel electrodes 16B disposed on the first transparent substrate 10 and an electric field generated between the second pixel electrodes 16B and a second common electrode 24 disposed on a second transparent substrate 20. Display states or non-display states of the first and the second sub pixels 1A and 1B are switched by first and second switching circuits 103 and 104. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device capable of switching a viewing angle.

  As one of the liquid crystal display devices equipped with a liquid crystal display panel, both a narrow viewing angle for maintaining the privacy of the display screen and a wide viewing angle for disclosing the display screen to a large number of viewers are required. There are known liquid crystal display devices that can be switched.

  In such a liquid crystal display device, as shown in FIG. 9, a viewing angle control panel 202 for controlling a viewing angle is provided on a liquid crystal display panel 201 for display. The viewing angle control panel 202 is composed of, for example, a laminate in which a liquid crystal layer is sealed between two transparent substrates, and controls the voltage applied to the liquid crystal layer to change the phase difference of the liquid crystal layer. The viewing angle of the display screen of the liquid crystal display panel 201 is switched.

Note that a liquid crystal display device that switches a viewing angle using a viewing angle control panel is described in Patent Document 1.
JP 2006-201326 A

  In the above-described liquid crystal display device, since the viewing angle control panel 202 is provided so as to be laminated on the liquid crystal display panel 201, there has been a problem that the thickness and weight of the entire liquid crystal display device increase. Further, since the manufacturing cost of the viewing angle control panel 202 is high, the manufacturing cost of the entire liquid crystal display device is also high.

  The liquid crystal display device of the present invention has been made in view of the above problems, and includes a pixel that performs display in accordance with a video signal, and the pixel includes a liquid crystal sandwiched between a first substrate and a second substrate. A first sub-pixel having a wide viewing angle in which the orientation of the liquid crystal is controlled by an electric field between the first pixel electrode and the first common electrode disposed on the first substrate, and the first sub-pixel disposed on the first substrate. The orientation of the liquid crystal is controlled by the electric field between the second pixel electrode and the first common electrode and the electric field between the second pixel electrode and the second common electrode disposed on the second substrate. The second sub-pixel having a narrow viewing angle, and further controlling the display state or non-display state of the first sub-pixel and the second sub-pixel to display a wide viewing angle and a narrow viewing angle. A switching circuit for switching to either display or high luminance display is provided.

  In the liquid crystal display device of the present invention, in the above-described configuration, in the wide viewing angle display, the switching circuit generates an electric field according to the video signal between the first pixel electrode and the first common electrode. The liquid crystal orientation of the sub-pixel is changed, and the electric field between the second pixel electrode and the second common electrode is controlled to keep the liquid crystal of the second sub-pixel in the initial orientation.

  In the liquid crystal display device of the present invention having the above structure, in the narrow viewing angle display, the electric field between the first pixel electrode and the first common electrode is controlled by the switching circuit by the switching circuit. While maintaining the liquid crystal in the initial alignment, an electric field corresponding to the video signal is generated between the second pixel electrode and the first common electrode while an electric field is generated between the second pixel electrode and the second common electrode. This is characterized in that the orientation of the liquid crystal of the second sub-pixel is changed.

  In the liquid crystal display device of the present invention, in the above configuration, in high luminance display, the switching circuit generates an electric field according to the video signal between the first pixel electrode and the first common electrode. The liquid crystal orientation of the sub-pixel is changed, and an electric field corresponding to a video signal is generated between the second pixel electrode and the first common electrode to change the liquid crystal orientation of the second sub-pixel. And

  According to this configuration, the first sub-pixel having a wide viewing angle and the second sub-pixel having a narrow viewing angle are provided in one pixel, and the display state or non-display state is switched by the switching circuit. Thus, the viewing angle can be switched. Therefore, compared with the liquid crystal display device in which the viewing angle can be switched as in the conventional example, it is possible to reduce the thickness and weight and to reduce the manufacturing cost.

  According to the present invention, in a liquid crystal display device in which the viewing angle can be switched, the thickness and weight of the liquid crystal display device can be reduced, and the manufacturing cost can be reduced.

  A liquid crystal display device according to an embodiment of the present invention will be described. This liquid crystal display device will be described assuming that it operates mainly in a lateral electric field type FFS (Fringe-Field Switching) mode. First, a schematic equivalent circuit of the liquid crystal display device will be described with reference to the drawings. FIG. 1 is an equivalent circuit diagram of the liquid crystal display device according to the present embodiment. FIG. 1 shows only some of the plurality of pixels 1 included in the liquid crystal display device.

As shown in FIG. 1, in each regularly arranged pixel 1, a first subpixel 1A having a wide viewing angle and a second subpixel 1B having a narrow viewing angle are adjacent to each other as a pair. Are arranged.
Each first sub-pixel 1A has a plurality of pixel selection signal lines GL to which pixel selection signals are supplied from the vertical drive circuit 101 and display signal lines DL1 to which display signals Vp1 are supplied from the horizontal drive circuit 102. It is arranged corresponding to. Each of the second sub-pixels 1B is arranged corresponding to each intersection of the plurality of pixel selection signal lines GL and the display signal line DL2 to which the display signal Vp2 is supplied from the horizontal drive circuit 102. The first sub pixel 1A and the second sub pixel 1B are alternately arranged in the column direction.

  In each first subpixel 1A and each second subpixel 1B, a pixel transistor TR such as a thin film transistor having a gate connected to the pixel selection signal line GL and a drain connected to the display signal lines DL1 and DL2 is disposed. ing. A pixel electrode (not shown) is connected to the source of the pixel transistor TR, and an electric field is formed in the liquid crystal layer LC by the pixel electrode and the common electrode (not shown).

  The first sub-pixel 1A and the second sub-pixel 1B control the display state or non-display state of the first sub-pixel 1A and the second sub-pixel 1B to switch to any one of the wide viewing angle display, the narrow viewing angle display, and the high luminance display. The switching circuit 103 and a second switching circuit (not shown) are connected. In the wide viewing angle display, switching is performed so that the first sub-pixel 1A is in the display state and the second sub-pixel 1B is in the non-display state. In narrow viewing angle display, switching is performed so that the first sub-pixel 1A is in a non-display state and the second sub-pixel 1B is in a display state. In the high luminance display, the first sub-pixel 1A and the second sub-pixel 1B are switched so as to be in the display state.

  Note that the first switching circuit 103 may be provided in the horizontal drive circuit 102 or may be provided outside the horizontal drive circuit 102. Furthermore, the first switching circuit 103 and the second switching circuit 104 may be configured as one circuit. Details of the switching operation of the first switching circuit 103 and the second switching circuit 104 will be described after the detailed configuration of the liquid crystal display device is described.

  Hereinafter, a detailed configuration of the liquid crystal display device will be described with reference to the drawings. FIG. 2 is a plan view showing the liquid crystal display device according to the present embodiment. In FIG. 2, for convenience of explanation, only one pixel 1 is shown among the plurality of pixels 1, and only main components on the first transparent substrate 10 side are illustrated. FIG. 3 shows a cross section taken along the line XX of FIG. 2 and shows a black display state in the wide viewing angle display. In FIG. 2 and FIG. 3, the same components as those shown in FIG.

  As shown in FIGS. 2 and 3, the liquid crystal layer LC is sandwiched between the first transparent substrate 10 and the second transparent substrate 20 disposed to face the first transparent substrate 10. In the first sub-pixel 1A and the second sub-pixel 1B, the first polarizing plate 11 is disposed on the first transparent substrate 10 on the side facing the light source BL. On the first transparent substrate 10 on the side not facing the light source BL, a pixel transistor TR, a pixel selection signal line GL, display signal lines DL1, DL2, and the like are arranged, and a planarizing film 13 is arranged to cover them. Yes. In FIG. 3, only the display signal lines DL1 and DL2 are shown.

  In the first subpixel 1A and the second subpixel 1B, a first common electrode 14 to which a common potential is applied is formed on the planarization film 13. The first common electrode 14 is made of a transparent conductive material such as ITO (Indium Tin Oxide). The common potential applied to the first common electrode 14 may be a fixed potential according to the driving method of the liquid crystal display device, or may be one in which the positive polarity and the negative polarity are alternately inverted.

  In the first subpixel 1A and the second subpixel 1B, the first common electrode 14 is covered with an insulating film 15. A first pixel electrode 16A in which a plurality of linear portions and slits are alternately arranged in parallel is disposed on the insulating film 15 in the first sub-pixel 1A. A display signal Vp1 is applied to the first pixel electrode 16A. A second pixel electrode 16B in which a plurality of linear portions and slits are alternately arranged in parallel is disposed on the insulating film 15 in the second subpixel 1B. A display signal Vp2 is applied to the second pixel electrode 16B. The first pixel electrode 16A and the second pixel electrode 16B are made of a transparent conductive material such as ITO.

  The insulating film 15, the first pixel electrode 16 </ b> A, and the second pixel electrode 16 </ b> B are covered with the alignment film 17. The rubbing direction of the alignment film 17 is parallel to or orthogonal to the transmission axis of the first polarizing plate 11, and in the plane horizontal to the first transparent substrate 10, the first pixel electrode It has an inclination angle of about 5 degrees to about 10 degrees with respect to the long side direction of 16A and the second pixel electrode 16B. In the following description, the case where the rubbing direction of the alignment film 17 is parallel to the transmission axis of the first polarizing plate 11 will be described as an example.

  On the other hand, on the side of the second transparent substrate 20 that does not face the first transparent substrate 10, the transmission perpendicular to the transmission axis of the first polarizing plate 11 in the first sub-pixel 1 </ b> A and the second sub-pixel 1 </ b> B. A second polarizing plate 21 having an axis is disposed.

  On the second transparent substrate 20 on the side facing the first transparent substrate 10, color filters (not shown) are formed in the first subpixel 1A and the second subpixel 1B. On the color filter of the first sub-pixel 1A, a cell is provided as a protrusion for adjusting the cell gap of the first sub-pixel 1A to be about half of the cell gap of the second sub-pixel 1B. A gap adjusting layer 23 is formed. The cell gap adjusting layer 23 is made of, for example, an acrylic resin and has a thickness of about 3 μm. A second common electrode 24 made of a transparent conductive material such as ITO is formed on the color filter of the second subpixel 1B. The cell gap adjusting layer 23 and the second common electrode 24 are covered with an alignment film 27 having a rubbing direction parallel to the rubbing direction of the alignment film 17 on the first transparent substrate 10 side. In the above configuration, the cell gap of the first subpixel 1A is preferably about 3.0 μm, and the cell gap of the second subpixel 1B is about 6.0 μm.

  The liquid crystal molecules M of the liquid crystal layer LC sandwiched between the first transparent substrate 10 and the second transparent substrate 20 described above are rubbed in the rubbing direction of the alignment films 17 and 27 parallel to the transmission axis of the first polarizing plate 11. Depending on the initial orientation. The liquid crystal molecules M of the liquid crystal layer LC have a positive dielectric anisotropy Δε, and the major axis direction rotates along the direction of the electric field. The positive dielectric anisotropy Δε is 5.0 to 15.0, preferably about 10.0. The birefringence value Δn of the liquid crystal molecules M is 0.1 to 0.2, preferably about 0.15.

  The operation of this liquid crystal display device will be described below. 4A and 4B are conceptual diagrams showing the internal states of the first switching circuit 103 and the second switching circuit 104. FIG. 4A shows a wide viewing angle display and FIG. 4B shows a narrow viewing angle display. FIG. 4C corresponds to high luminance display.

  FIG. 5 is a waveform diagram of each voltage applied to the first common electrode 14, the second pixel electrode 16B, and the second common electrode 24 in the second sub-pixel 1B. 5A corresponds to a non-display state, FIG. 5B corresponds to black display in the display state, and FIG. 5C corresponds to white display in the display state. In FIG. 5, the voltage applied to the first common electrode 14 (ie, the voltage corresponding to the common potential) is represented as Vcom1, the voltage applied to the second common electrode 24 is represented as Vcom2, and these voltages Vcom1, Vcom2 are represented. The display signal Vp2 applied to the second pixel electrode 16B is illustrated as having an amplitude with a constant period. The numerical values in parentheses in FIG. 5 are examples of specific values of the voltages or their potential differences.

  6, 7, and 8 are cross sections taken along line XX in FIG. 2. FIG. 6 shows a white display state in the wide viewing angle display. FIG. 7 shows the black display state in the narrow viewing angle display, and FIG. 8 shows the white display state. 4 to 8, the same components as those shown in FIG. 1 are referred to with the same reference numerals.

  First, the operation of the liquid crystal display device in wide viewing angle display will be described. As shown in FIG. 4A, the first switching circuit 103 is provided with a switch SW1 that connects either the video signal or the off potential to the display signal line DL1 of the first sub-pixel 1A. Similarly, a switch SW2 that connects either the video signal or the off-potential to the display signal line DL2 of the second sub-pixel 1B is disposed. In the second switching circuit 104, a switch SW3 for connecting either the high potential or the off potential to the second common electrode 24 is disposed.

  Here, the video signal is a voltage signal that changes in a range from a black display potential to a white display potential corresponding to the video. The off-potential means between the first common electrode 14 and the first pixel electrode 16A and between the first common electrode 14 and the second pixel electrode in the first subpixel 1A and the second subpixel 1B. Between 16B, this means a potential that maintains the initial alignment without changing the alignment of the liquid crystal molecules M of the liquid crystal layer LC. This off potential is used to control one of the sub-pixels to a non-display state, that is, an off state. The high potential is an electric field perpendicular or substantially perpendicular to the first transparent substrate 10 between the second pixel electrode 16B and the second common electrode 24 in the second sub-pixel 1B. And a potential that changes the orientation of the liquid crystal molecules M.

  In the wide viewing angle display, the first switching circuit 103 supplies the video signal as the display signal Vp1 to the display signal line DL1 of the first sub-pixel 1A that is in the display state by switching the switch SW1. The display signal Vp1 is applied to the first pixel electrode 16A through a pixel transistor (not shown). Further, by switching the switch SW2, the off-potential display signal Vp2 is supplied to the display signal line DL2 of the second sub-pixel 1B that is in the non-display state regardless of the black display and the white display of the first sub-pixel 1A. Is done. The off-potential display signal Vp2 is applied to the second pixel electrode 16B through the pixel transistor. In the second switching circuit 104, the off potential is applied to the second common electrode 24 by switching the switch SW3.

  As shown in FIG. 3, in the black display of the first subpixel 1A that is in the display state in the wide viewing angle display, the first pixel electrode 16A has a potential corresponding to the black display of the video signal as the display signal Vp1. Therefore, an electric field that changes the orientation of the liquid crystal molecules M of the liquid crystal layer LC does not occur between the first common electrode 14 and the first pixel electrode 16A. Therefore, in the first sub-pixel 1 </ b> A, the liquid crystal molecules M maintain the initial alignment along the rubbing direction in a plane substantially horizontal to the first transparent substrate 10.

  In the first sub-pixel 1A in this state, the light of the light source BL linearly polarized by the first polarizing plate 11 passes through the liquid crystal layer LC with the polarization axis as it is and enters the second polarizing plate 21. However, this light is absorbed by the second polarizing plate 21 because its polarization axis is orthogonal to the transmission axis of the second polarizing plate 21. That is, black display (normally black) is obtained.

  On the other hand, the second pixel electrode 16B in the second subpixel 1B has an off-potential as the display signal Vp2 as shown in FIG. 5A regardless of the black display and white display of the first subpixel 1A. Therefore, an electric field that changes the alignment of the liquid crystal molecules M does not occur between the first common electrode 14 and the second pixel electrode 16B. In addition, since the off potential is also applied to the second common electrode 24, an electric field that changes the alignment of the liquid crystal molecules M does not occur between the second pixel electrode 16B and the second common electrode 24. Therefore, the liquid crystal molecules M of the second sub-pixel 1B maintain the initial alignment along the rubbing direction in a substantially horizontal plane with respect to the first transparent substrate 10, and display black by the optical principle similar to the above. Become non-display state.

  As shown in FIG. 6, in the white display of the first sub-pixel 1A that is in the display state with the wide viewing angle display, the first pixel electrode 16A has a potential corresponding to the white display of the video signal as the display signal Vp1. Therefore, the orientation of the liquid crystal molecules M of the liquid crystal layer LC is changed between the first common electrode 14 and the first pixel electrode 16A in a substantially horizontal direction with respect to the first transparent substrate 10. An electric field is generated. Therefore, in the first sub-pixel 1A, the liquid crystal molecules M are not parallel or orthogonal to the long-side direction of the first pixel electrode 16A in a plane substantially horizontal to the first transparent substrate 10. Rotate to tilt at an angle that does not.

  In the first sub-pixel 1 </ b> A in this state, the light of the light source BL linearly polarized by the first polarizing plate 11 becomes elliptically polarized light due to birefringence in the liquid crystal layer LC and enters the second polarizing plate 21. Among the elliptically polarized light, a component that coincides with the transmission axis of the second polarizing plate 21 is emitted and white display is performed.

  On the other hand, the second pixel electrode 16B in the second subpixel 1B has an off-potential as the display signal Vp2 as shown in FIG. 5A regardless of the black display and white display of the first subpixel 1A. Since the voltage is applied, the second sub-pixel 1B becomes black and is not displayed.

  In this way, in the first sub-pixel 1A in the display state, the liquid crystal molecules M are aligned substantially horizontally with respect to the first transparent substrate 10 in both black display and white display, so that unnecessary birefringence does not occur. Wide viewing angle display is performed. At this time, the second sub-pixel 1B having a narrow viewing angle is not displayed, and thus does not contribute to display.

  The operation of the liquid crystal display device in the narrow viewing angle display will be described below. As shown in FIG. 4B, in the narrow viewing angle display, the first switching circuit 103 switches the switch SW1, regardless of whether the second subpixel 1B in the display state is black or white. An off-potential display signal Vp1 is supplied to the display signal line DL1 of the first sub-pixel 1A that is in a non-display state. The off-potential display signal Vp1 is applied to the first pixel electrode 16A through a pixel transistor (not shown).

  Further, by switching the switch SW2, the video signal is supplied as the display signal Vp2 to the display signal line DL2 of the second sub-pixel 1B in the display state. The display signal Vp2 is applied to the second pixel electrode 16B through the pixel transistor. Further, in the second switching circuit 104, a high potential at a level that generates an electric field between the second pixel electrode 16B and the second common electrode 24 is generated in the second common electrode 24 by switching the switch SW3. Applied. At this time, the potential difference ΔVgap between the second pixel electrode 16B and the second common electrode 24 is a level that exceeds a threshold value at which the orientation of the liquid crystal molecules M changes along a substantially vertical direction with respect to the first transparent substrate 10. For example, it is about 1V or more. The voltage applied to the second common electrode 24 so as to generate this potential difference ΔVgap has a waveform as shown in FIGS. 5B and 5C, for example.

  As shown in FIG. 5B and FIG. 7, in the black display of the second sub-pixel 1B which is in the display state with the narrow viewing angle display, the black of the video signal is displayed as the display signal Vp2 on the second pixel electrode 16B. Since a potential corresponding to display is applied, an electric field that changes the orientation of the liquid crystal molecules M of the liquid crystal layer LC does not occur between the first common electrode 14 and the second pixel electrode 16B. On the other hand, the orientation of the liquid crystal molecules M changes between the second pixel electrode 16B and the second common electrode 24 in a direction substantially perpendicular to the first transparent substrate 10 according to the potential difference ΔVgap. An electric field is generated. Therefore, in the second sub-pixel 1B, the liquid crystal molecules M are aligned in the substantially vertical direction with respect to the first transparent substrate 10 and are aligned in the rubbing direction.

  In the second sub-pixel 1B in this state, the light of the light source BL linearly polarized by the first polarizing plate 11 passes through the liquid crystal layer LC with the polarization axis as it is and enters the second polarizing plate 21. However, this light is absorbed by the second polarizing plate 21 because its polarization axis is orthogonal to the transmission axis of the second polarizing plate 21. That is, black display (normally black) is obtained. At this time, since the liquid crystal molecules M are also aligned in a direction substantially perpendicular to the first transparent substrate 10, a component that transmits through the second polarizing plate 21 occurs due to birefringence at a low viewing angle, which is desired. The black display cannot be obtained. That is, black display with a narrow viewing angle is performed.

  On the other hand, an off-potential is applied as the display signal Vp1 to the first pixel electrode 16A in the first subpixel 1A regardless of the black display and white display of the second subpixel 1B. An electric field that changes the alignment of the liquid crystal molecules M does not occur between the electrode 14 and the first pixel electrode 16A. For this reason, the liquid crystal molecules M of the first sub-pixel 1A maintain the initial alignment along the rubbing direction in a substantially horizontal plane with respect to the first transparent substrate 10, so that they do not contribute to black display, that is, display. Display state.

  As shown in FIG. 5C and FIG. 8, in the white display of the second subpixel 1B that is in the display state with the narrow viewing angle display, the white signal of the video signal is displayed as the display signal Vp2 on the second pixel electrode 16B. Since the potential corresponding to the display is supplied, the liquid crystal molecules of the liquid crystal layer LC are disposed between the first common electrode 14 and the second pixel electrode 16B in a substantially horizontal direction with respect to the first transparent substrate 10. An electric field is generated that changes the orientation of M. At the same time, the orientation of the liquid crystal molecules M changes between the second pixel electrode 16B and the second common electrode 24 in a direction substantially perpendicular to the first transparent substrate 10 according to the potential difference ΔVgap. An electric field is generated.

  Therefore, in the second sub-pixel 1B, the liquid crystal molecules M are aligned in a substantially vertical direction with respect to the first transparent substrate 10, and the second liquid crystal molecules M are aligned in a plane substantially horizontal with respect to the first transparent substrate 10. The pixel electrode 16B is rotated so as to be inclined at an angle that is not parallel to the long side direction or an angle that is not orthogonal to the long side direction.

  In the second sub-pixel 1 </ b> B in this state, the light of the light source BL linearly polarized by the first polarizing plate 11 becomes elliptically polarized light due to birefringence in the liquid crystal layer LC and enters the second polarizing plate 21. Among the elliptically polarized light, a component that coincides with the transmission axis of the second polarizing plate 21 is emitted and white display is performed. At that time, since the liquid crystal molecules M are also aligned in a direction substantially perpendicular to the first transparent substrate 10, the component transmitted through the second polarizing plate 21 decreases at a low viewing angle, and the desired white The display cannot be obtained. That is, white display with a narrow viewing angle is performed.

  On the other hand, an off-potential is applied as the display signal Vp1 to the first pixel electrode 16A in the first sub-pixel 1A regardless of the black display and white display of the second sub-pixel 1B. The pixel 1A is in black display and is in a non-display state that does not contribute to display.

  The operation of the liquid crystal display device in high luminance display will be described below. This high luminance display is performed, for example, when priority is given to higher luminance than switching of the viewing angle. As shown in FIG. 4C, in the high luminance display, in the first switching circuit 103, the switching of the switch SW1 and the switch SW2 causes the first subpixel 1A and the second subpixel 1B to be in the display state. Video signals are supplied to the respective display signal lines DL1 and DL2 as display signals Vp1 and Vp2. These display signals Vp1 and Vp2 are applied to the first pixel electrode 16A and the second pixel electrode 16B through pixel transistors (not shown), respectively. In the second switching circuit 104, a high potential is applied to the second common electrode 24 by switching the switch SW3.

  The black display and the white display of the first sub-pixel 1A in the high luminance display are performed in the same manner as the black display and the white display in the wide viewing angle display shown in FIGS. Further, the black display and the white display of the second sub-pixel 1B in the high luminance display are the black display and the white display in the narrow viewing angle display shown in FIG. 5 (B), FIG. 5 (C), FIG. 7 and FIG. This is done in the same way as the display. Thereby, since both the first sub-pixel 1A and the second sub-pixel 1B are in the display state, display can be performed with high luminance.

  By the way, in the liquid crystal layer LC of the first sub-pixel 1A and the second sub-pixel 1B, when birefringence occurs, if the thickness of the region having the phase difference contributing to display is the same, The luminance of the pixel 1A is larger than the luminance of the second sub-pixel 1B. This is because, in the second sub-pixel 1B, the light transmitted through the second polarizing plate 21 when birefringence occurs by the amount that the liquid crystal molecules M are aligned in a direction substantially perpendicular to the first transparent substrate 10 as well. This is because there are fewer components.

  In contrast, in the present embodiment, the cell gap of the first subpixel 1A is adjusted to be smaller than the cell gap of the second subpixel 1B by the cell gap adjustment layer 23. Therefore, when birefringence occurs in the liquid crystal layer LC of the first sub-pixel 1A and the second sub-pixel 1B, the light component transmitted through the second polarizing plate 21 becomes the first sub-pixel 1A and the second sub-pixel 1A. It is possible to prevent the subpixel 1B from being biased. Thereby, the variation in the brightness | luminance in the whole pixel 1 is reduced, and a display quality can be improved. However, the cell gap adjustment layer 23 may not be arranged when there is no need to consider the luminance variation in the entire pixel 1.

  Note that when higher luminance display or wide viewing angle display is required in high luminance display, an off potential is applied to the second common electrode 24 by switching the switch SW3 of the second switching circuit 104. May be. In this case, an electric field that changes the orientation of the liquid crystal molecules M of the second sub-pixel 1B does not occur between the second pixel electrode 16B and the second common electrode 24. It is not oriented in a direction substantially perpendicular to the transparent substrate 10. That is, the liquid crystal molecules M of the second sub-pixel 1B rotate along an electric field corresponding to the display signal Vp2 in a plane substantially horizontal to the first transparent substrate 10. Thereby, in the white display of the second sub-pixel 1B, the light component transmitted through the second polarizing plate 21 is not reduced, and a high luminance and a wide viewing angle are obtained. As a result, the brightness of the entire pixel 1 is further increased, and a display with a wider viewing angle can be obtained.

  The liquid crystal display device of the above embodiment is assumed to operate in the FFS mode. However, the present invention is not limited to this, and an electric field in a substantially horizontal direction with respect to the first transparent substrate 10 is used according to the video signal. As long as it controls the orientation of the liquid crystal molecules M, it may operate in other modes. For example, the liquid crystal display device of the present invention may operate in an IPS (In-Plain Switching) mode. In this case, in the first sub-pixel 1A and the second sub-pixel 1B, a plurality of first common electrodes are linearly arranged on the first transparent substrate 10, and between the first common electrodes, Linear pixel electrodes are alternately arranged with a predetermined interval. In the second sub-pixel 1B, the second common electrode 24 is disposed on the second transparent substrate 20 so as to face the first common electrode and the pixel electrode.

1 is a schematic equivalent circuit diagram of a liquid crystal display device according to an embodiment of the present invention. It is a top view which shows the liquid crystal display device by embodiment of this invention. It is sectional drawing which shows the liquid crystal display device by embodiment of this invention. 3 is a conceptual diagram of a first switching circuit and a second switching circuit of the liquid crystal display device according to the embodiment of the present invention. FIG. It is a wave form diagram of each voltage applied to the 1st common electrode in the 2nd sub pixel, the 2nd pixel electrode, and the 2nd common electrode. It is sectional drawing which shows the liquid crystal display device by embodiment of this invention. It is sectional drawing which shows the liquid crystal display device by embodiment of this invention. It is sectional drawing which shows the liquid crystal display device by embodiment of this invention. It is sectional drawing which shows the liquid crystal display device by a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pixel 1A 1st subpixel 1B 2nd subpixel 10 1st transparent substrate 11 1st polarizing plate 13 Planarizing film 14 1st common electrode 15 Insulating film 16A 1st pixel electrode 16B 2nd pixel Electrodes 17 and 27 Alignment film 20 Second transparent substrate
21 Second polarizing plate 23 Cell gap adjusting layer 24 Second common electrode 101 Vertical driving circuit 102 Horizontal driving circuit 103 First switching circuit 104 Second switching circuit 201 Liquid crystal display panel 202 Viewing angle control panel BL Light source LC Liquid crystal Layer M Liquid crystal molecule TR Pixel transistor GL Pixel selection signal line DL1, DL2 Display signal line

Claims (5)

A pixel that performs display in response to a video signal,
A liquid crystal sandwiched between the first substrate and the second substrate;
A first sub-pixel having a wide viewing angle in which the orientation of the liquid crystal is controlled by an electric field between a first pixel electrode and a first common electrode disposed on the first substrate;
An electric field between the second pixel electrode disposed on the first substrate and the first common electrode; and a second common electrode disposed on the second pixel electrode and the second substrate; A second sub-pixel having a narrow viewing angle in which the orientation of the liquid crystal is controlled by an electric field between
And a switching circuit that controls the display state or non-display state of the first sub-pixel and the second sub-pixel to switch to either wide viewing angle display, narrow viewing angle display, or high luminance display. A liquid crystal display device characterized by the above.   In the wide viewing angle display, an electric field corresponding to the video signal is generated between the first pixel electrode and the first common electrode by the switching circuit, thereby aligning the liquid crystal of the first sub-pixel. The liquid crystal of the second sub-pixel is maintained in an initial alignment by controlling an electric field between the second pixel electrode and the second common electrode, and changing the electric field between the second pixel electrode and the second common electrode. The liquid crystal display device described.   In the narrow viewing angle display, the switching circuit controls the electric field between the first pixel electrode and the first common electrode to keep the liquid crystal of the first sub-pixel in the initial orientation, An electric field corresponding to the video signal is generated between the second pixel electrode and the first common electrode while an electric field is generated between the second pixel electrode and the second common electrode. The liquid crystal display device according to claim 1, wherein the orientation of the liquid crystal of the second subpixel is changed.   In the high luminance display, the switching circuit generates an electric field according to the video signal between the first pixel electrode and the first common electrode, thereby aligning the liquid crystal of the first sub-pixel. And changing the orientation of the liquid crystal of the second sub-pixel by generating an electric field according to the video signal between the second pixel electrode and the first common electrode. The liquid crystal display device according to claim 1.   5. The liquid crystal display device according to claim 1, wherein a cell gap of the second sub-pixel is larger than a cell gap of the first sub-pixel.

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