JPWO2008023601A1 - Liquid crystal display - Google Patents

Abstract

Each of the liquid crystal display devices of the present invention includes a plurality of pixels including a first subpixel and a second subpixel, and performs display of a predetermined intermediate gradation over four or more consecutive vertical scanning periods. In this case, the luminance values of the first sub-pixel and the second sub-pixel are different in at least two vertical scanning periods among the even-numbered vertical scanning periods. The length of the first polarity period in which the polarity is the first polarity is equal to the length of the second polarity period in which the polarity is the second polarity, and the liquid crystal layer of the first subpixel in each of the first polarity period and the second polarity period The difference between the average value of the effective voltages applied to the liquid crystal layer and the average value of the effective voltages applied to the liquid crystal layer of the second subpixel is substantially zero.

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device with improved viewing angle dependency of γ characteristics.

  The liquid crystal display device is a flat display device having excellent features such as high definition, thinness, light weight and low power consumption. In recent years, the display performance has been improved, the production capacity has been improved, and the price competitiveness with respect to other display devices has been improved. As a result, the market scale is expanding rapidly.

  In a conventional twisted nematic mode (TN mode) liquid crystal display device, the major axis of liquid crystal molecules having positive dielectric anisotropy is substantially parallel to the substrate surface, and the liquid crystal layer The alignment treatment is performed so that the substrate is twisted approximately 90 degrees between the upper and lower substrates along the thickness direction. When a voltage is applied to the liquid crystal layer, the liquid crystal molecules rise in parallel with the electric field, and the twist alignment (twist alignment) is eliminated. In a TN mode liquid crystal display device, the amount of transmitted light is controlled by utilizing a change in optical rotation accompanying a change in the orientation of liquid crystal molecules due to a voltage.

  Such a TN mode liquid crystal display device has a wide production margin and excellent productivity, but has a problem in display performance, particularly viewing angle characteristics. Specifically, when the display surface of a TN mode liquid crystal display device is observed from an oblique direction, the contrast ratio of the display is significantly reduced, and a plurality of gradations from black to white are clearly observed when observed from the front. When the image is observed from an oblique direction, the problem is that the luminance difference between gradations becomes extremely unclear. Furthermore, the phenomenon that the gradation characteristics of the display are reversed and a darker portion when observed from the front is observed brighter when observed from an oblique direction (so-called gradation inversion phenomenon) is also a problem.

  In recent years, liquid crystal display devices with improved viewing angle characteristics in TN mode liquid crystal display devices include in-plane switching mode (IPS mode), multi-domain vertical aligned mode (MVA mode), and axially symmetric alignment mode (ASM). Mode) and the like have been developed. In these novel mode (wide viewing angle mode) liquid crystal display devices, the above-mentioned specific problems related to viewing angle characteristics, that is, a significant reduction in display contrast ratio when the display surface is observed obliquely, and Problems such as display gradation inversion have been solved.

  However, under the circumstances where the display quality of liquid crystal display devices is improving, the problem of viewing angle characteristics is that the γ characteristics during frontal observation and the γ characteristics during oblique observation differ, that is, the dependence of γ characteristics on the viewing angle. Sexual problems are newly emerging. Here, the γ characteristic is the gradation dependency of the display luminance. The fact that the γ characteristic is different between the front direction and the diagonal direction means that the gradation display state differs depending on the observation direction. This is particularly a problem when displaying, or when displaying TV broadcasts and the like.

  As a method for improving the viewing angle dependency of the γ characteristic, two or more subpixels are provided in one pixel, and the luminance of one subpixel is different from the other in the intermediate luminance display. Methods for improving the viewing angle dependency are known (see, for example, Patent Document 1 and Patent Document 2).

  In the liquid crystal display device disclosed in Patent Document 1, by changing the effective voltage of the liquid crystal layer of the second subpixel in the intermediate luminance display from the effective voltage of the liquid crystal layer of the first subpixel, The luminance and the luminance of the second sub-pixel are made different, thereby improving the viewing angle dependency of the γ characteristic. Since the transmittance of the liquid crystal layer changes according to the absolute value of the effective voltage regardless of the direction of the electric field applied to the liquid crystal layer (the direction of the lines of electric force), the liquid crystal display device disclosed in Patent Document 1 Then, by reversing the direction of the electric field applied to the liquid crystal layer alternately every vertical scanning period, the bias of the DC component (DC level) is suppressed and the problem of reliability such as burn-in is solved. .

  In the liquid crystal display device disclosed in Patent Document 2, the brightness of the first subpixel and the second subpixel is inverted every vertical scanning period (for example, the luminance of the first subpixel is changed in the first vertical scanning period). The luminance of the second subpixel is set to be higher than the luminance of the first subpixel in the second vertical scanning period, and the direction of the electric field applied to the liquid crystal layer is set to the vertical scanning period. It is reversed every time. If one of the plurality of subpixels is always bright, the display may appear rough. However, in the liquid crystal display device disclosed in Patent Document 2, the first subpixel and the second subpixel are displayed every vertical scanning period. Roughness of the display is prevented by reversing the brightness of the subpixels.

Note that, as described above, display or driving for improving the viewing angle dependency of γ characteristics by changing the luminance of a plurality of sub-pixels is referred to as multi-pixel display, multi-pixel driving, area gradation in this specification. It may be called display, area gradation drive, or the like.
JP 2004-62146 A JP 2003-295160 A (US Pat. No. 6,958,791)

  In the liquid crystal display device of Patent Document 1, since the luminance of the first subpixel is always higher than the luminance of the second subpixel in the intermediate luminance display, the brightness of the subpixel is visually recognized and the display may appear rough.

  Further, in the liquid crystal display device of Patent Document 2, since the direction of the electric field applied to the liquid crystal layer and the brightness of the subpixel are inverted every vertical scanning period, one subpixel is brighter than the other subpixel. The direction of the electric field applied to the liquid crystal layer is always the same.

  For example, in the liquid crystal display device disclosed in Patent Document 2, the absolute value of the effective voltage applied to the first subpixel becomes larger than the absolute value of the effective voltage applied to the second subpixel in a certain vertical scanning period. When one subpixel is brighter than the second subpixel, the electric field applied to the liquid crystal layer is directed from the subpixel electrode side to the counter electrode side (the state in which the electric field is directed in this way is referred to as “first polarity”). . In the next vertical scanning period, the absolute value of the effective voltage applied to the second subpixel is larger than the absolute value of the effective voltage applied to the first subpixel, and the second subpixel is larger than the first subpixel. The electric field applied to the liquid crystal layer becomes brighter and is directed from the counter electrode side to the sub-pixel electrode side (the state in which the electric field is directed in this way is referred to as “second polarity”). In the next vertical scanning period, the absolute value of the effective voltage applied to the first subpixel is larger than the absolute value of the effective voltage applied to the second subpixel, and the first subpixel is the second subpixel. In the next vertical scanning period, the absolute value of the effective voltage applied to the second subpixel is larger than the absolute value of the effective voltage applied to the first subpixel, The second subpixel is brighter than the first subpixel and has the second polarity.

  As described above, in the liquid crystal display device disclosed in Patent Document 2, when the absolute value of the effective voltage applied to the first subpixel is large, the liquid crystal display device has the first polarity exclusively, and the absolute value of the effective voltage applied to the second subpixel. Since the second polarity is exclusively used when the value is large, the average value of the effective voltage applied to the first subpixel is the first polarity, and the average value of the effective voltage applied to the second subpixel is the second polarity. Become.

  Note that a general liquid crystal display device displays the same image for a long time in a state where the average value of the voltage applied to the pixel is not zero, that is, in a state where a DC voltage component remains in the voltage applied to the pixel. If this is continued, a phenomenon called burn-in occurs in which an image that has been displayed for a long time remains after switching the display image. In order to avoid this burn-in, in a general liquid crystal display device, a pixel is applied to a liquid crystal layer by alternating current driving (a first polarity voltage and a second polarity voltage having the same absolute value are alternately applied). The average voltage is set to zero. Further, when the average value of the voltage does not become zero due to AC driving, the average value of the voltage is set to zero by further adjusting the counter voltage.

  However, in the liquid crystal display device of Patent Document 2, since the average values of the effective voltages of the first subpixel and the second subpixel are different, even if the counter voltage is adjusted, one subpixel can be made zero. Only, and the average value of the voltages for the other sub-pixel cannot be adjusted to zero. In this case, burn-in occurs in the sub-pixels that could not be adjusted, and as a result, the occurrence of burn-in cannot be suppressed as the entire display device. Therefore, in the liquid crystal display device of Patent Document 2, the average value of the voltages applied to the first and second sub-pixels cannot be made zero, causing a problem in reliability such as burn-in. There is.

  The present invention has been made in view of the above problems, and an object thereof is to provide a liquid crystal display device in which occurrence of reliability problems such as display roughness and burn-in is suppressed.

  The liquid crystal display device of the present invention is a liquid crystal display device including a plurality of pixels each including a first subpixel and a second subpixel, wherein each of the first subpixel and the second subpixel is A counter electrode; a sub-pixel electrode; and a liquid crystal layer disposed between the counter electrode and the sub-pixel electrode, wherein each of the sub-pixels of the first sub-pixel and the second sub-pixel The electrodes are respectively separate first and second subpixel electrodes, and the counter electrodes of the first and second subpixels are a single common electrode, and are continuous four or more. In the case where a predetermined intermediate gradation is displayed over the even number of vertical scanning periods, the luminance values of the first subpixel and the second subpixel are different in at least two vertical scanning periods of the even number of vertical scanning periods. , The first sub-pixel and For each of the second sub-pixels, the length of the first polarity period in which the polarity of the even number of vertical scanning periods is the first polarity is equal to the length of the second polarity period which is the second polarity, and the first polarity A difference between an average value of effective voltages applied to the liquid crystal layer of the first subpixel and an average value of effective voltages applied to the liquid crystal layer of the second subpixel in each of the period and the second polarity period Is substantially zero.

  In one embodiment, in each of the plurality of pixels, an effective voltage applied to the liquid crystal layer of the first subpixel is VLspa, and an effective voltage applied to the liquid crystal layer of the second subpixel is VLspb. Then, of the four consecutive vertical scanning periods, two vertical scanning periods are the first polarity period, and the remaining two vertical scanning periods are the second polarity period, and the first polarity period and the first polarity period Of at least one of the two polar periods, one of the two vertical scanning periods satisfies | VLspa |> | VLspb |, and the other satisfies | VLspa | <| VLspb |.

  In one embodiment, in each of the plurality of pixels, an effective voltage applied to the liquid crystal layer of the first subpixel is VLspa, and an effective voltage applied to the liquid crystal layer of the second subpixel is VLspb. Then, of the four consecutive vertical scanning periods, two vertical scanning periods are the first polarity period, and the remaining two vertical scanning periods are the second polarity period, and the first polarity period and the first polarity period The value of V | Lspa | and the value of | VLspb | in one of the two vertical scanning periods of at least one of the two polar periods is equal to the value of | VLspb | and | It is equal to the value of VLspa |.

  In one embodiment, the number of vertical scanning periods satisfying | VLspa |> | VLspb | of the four vertical scanning periods is equal to the number of vertical scanning periods satisfying | VLspa | <| VLspb |.

  In one embodiment, the plurality of pixels are arranged in a matrix in a plurality of row directions and a plurality of column directions, and in each of the plurality of pixels, the first subpixel and the second subpixel are Arranged along the column direction.

  In one embodiment, in each of the plurality of pixels, the voltages of the first subpixel electrode and the second subpixel electrode change according to a voltage change of a corresponding auxiliary capacitance line.

  In one embodiment, in each of the plurality of pixels, the voltage of the auxiliary capacitance line corresponding to the first subpixel electrode changes in a direction different from the voltage of the auxiliary capacitance line corresponding to the second subpixel electrode. .

  In one embodiment, the voltage of the second subpixel electrode of a pixel of the plurality of pixels and the voltage of the first subpixel electrode of a pixel adjacent to the pixel in the column direction are common. It changes according to the voltage change of the auxiliary capacity wiring.

  In one embodiment, the voltage of the second subpixel electrode of a certain pixel of the plurality of pixels and the voltage of the first subpixel electrode of a pixel adjacent to the certain pixel in the column direction are different assists. It changes according to the voltage change of the capacitor wiring.

  In one embodiment, in each of the plurality of pixels, the first subpixel electrode is connected to the same signal line as the second subpixel electrode via a corresponding switching element.

  In one embodiment, in each of the plurality of pixels, the first subpixel electrode is connected to a first signal line via a first switching element, and the second subpixel electrode is connected via a second switching element. Connected to the second signal line.

  In one embodiment, one of the two vertical scanning periods of the first polarity period and the second polarity period is a vertical scanning period that satisfies | VLspa |> | VLspb |, and the other is | VLspa |. This is a vertical scanning period that satisfies <| VLspb |.

  In one embodiment, in each of the plurality of pixels, the magnitude relation between | VLspa | and | VLspb | is inverted every one vertical scanning period, and the polarities of the first subpixel and the second subpixel are set to 2 Inversion occurs every vertical scanning period.

  In some embodiments, the frame frequency is 60 Hz.

  In one embodiment, in each of the plurality of pixels, the magnitude relation between | VLspa | and | VLspb | is inverted every two vertical scanning periods, and the polarities of the first subpixel and the second subpixel are set to 1 Inversion occurs every vertical scanning period.

  In some embodiments, the frame frequency is 120 Hz.

  In one embodiment, in each of the plurality of pixels, the magnitude relationship between | VLspa | and | VLspb | is inverted every two vertical scanning periods, and the polarities of the first subpixel and the second subpixel are set to 2 Inversion is performed every vertical scanning period, and the magnitude relationship between | VLspa | and | VLspb | is inverted when the polarity of the first subpixel and the second subpixel is different.

  In one embodiment, one of the two vertical scanning periods of the first polarity period and the second polarity period is a vertical scanning period that satisfies | VLspa |> | VLspb | and the other is | VLspa | VLspa is equal to VLspb in each of the other two vertical scanning periods of the first polarity period and the second polarity period.

  In one embodiment, the voltage of the auxiliary capacitance line corresponding to the first subpixel electrode and the second subpixel electrode is a first level, a second level higher than the first level, and the second level. It changes between a third level with a higher voltage than the level.

  In one embodiment, the first subpixel electrode has a display area equal to that of the second subpixel electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device which suppressed generation | occurrence | production of reliability problems, such as display roughness and image sticking, can be provided.

It is a schematic diagram which shows the structure of 1st Embodiment of the liquid crystal display device by this invention. It is a typical block diagram of the liquid crystal panel in the liquid crystal display device of 1st Embodiment. (A) is a schematic plan view of one pixel in the liquid crystal display device of 1st Embodiment, (b) is a typical sectional drawing of one subpixel. It is a schematic diagram which shows the change of the brightness of the 1st, 2nd subpixel in the conventional liquid crystal display device, a polarity, and an effective voltage, (a) is a model which shows the change of the brightness of the 1st, 2nd subpixel, and polarity FIG. 6B is a schematic diagram showing a change in effective voltage applied to the liquid crystal layer of the first subpixel, and FIG. 5C is a graph showing effective voltage applied to the liquid crystal layer of the second subpixel. It is a schematic diagram which shows a change. It is a schematic diagram which shows the change of the brightness of the 1st, 2nd subpixel, polarity, and effective voltage in another conventional liquid crystal display device, (a) shows the change of the brightness of the 1st, 2nd subpixel, and polarity. FIG. 4B is a schematic diagram showing a change in effective voltage applied to the liquid crystal layer of the first subpixel, and FIG. 4C is an effective diagram applied to the liquid crystal layer of the second subpixel. It is a schematic diagram which shows the change of a voltage. FIG. 3 is a schematic diagram showing changes in brightness, polarity, and effective voltage of first and second subpixels in the liquid crystal display device of the first embodiment, and FIG. 4A is a change in brightness and polarity of first and second subpixels. (B) is a schematic diagram showing a change in effective voltage applied to the liquid crystal layer of the first subpixel, and (c) is applied to the liquid crystal layer of the second subpixel. It is a schematic diagram which shows the change of an effective voltage. It is a schematic diagram which shows an example of the pixel structure of the liquid crystal display device of 1st Embodiment. FIG. 3 is an equivalent circuit diagram of one pixel in the liquid crystal display device of the first embodiment. It is a figure which shows an example of the various voltage waveforms used for the drive of the liquid crystal display device of 1st Embodiment. It is a figure which shows the relationship of the effective voltage applied to the liquid crystal layer of the subpixel in the liquid crystal display device of 1st Embodiment. It is a figure which shows the gamma characteristic of the liquid crystal display device of 1st Embodiment, (a) is a figure which shows the gamma characteristic in a right 60 degree viewing angle, (b) is a figure which shows the gamma characteristic of a right upper 60 degree viewing angle. is there. It is a figure which shows an example of the various voltage waveforms over the some vertical scanning period in the liquid crystal display device of 1st Embodiment. It is an example of the equivalent circuit schematic of the liquid crystal display device of 1st Embodiment. It is a schematic diagram which shows the arrangement | sequence of several subpixels, brightness and darkness, and polarity in the liquid crystal display device of 1st Embodiment. It is a figure which shows an example of the various voltage waveforms in the liquid crystal display device of 1st Embodiment. It is a figure which shows an example of the various voltage waveforms over the some vertical scanning period in the liquid crystal display device of 1st Embodiment. FIG. 6 is a schematic diagram illustrating the change in brightness and darkness and polarity of subpixels in the liquid crystal display device of the first embodiment, and the initial auxiliary capacitance voltage in the vertical scanning period of each subpixel. (A) And (b) is a figure which shows an example of the various voltage waveforms over the some vertical scanning period in the liquid crystal display device of 1st Embodiment. (A)-(c) is a figure which shows an example of the various voltage waveforms over the some vertical scanning period in the liquid crystal display device of 1st Embodiment. It is a figure which shows an example of the various voltage waveforms over the some vertical scanning period in the liquid crystal display device of 1st Embodiment. It is a figure which shows an example of the various voltage waveforms over the some vertical scanning period in the liquid crystal display device of 1st Embodiment. FIG. 6 is a schematic diagram illustrating the change in brightness and darkness and polarity of subpixels in the liquid crystal display device of the first embodiment, and the initial auxiliary capacitance voltage in the vertical scanning period of each subpixel. It is an example of the equivalent circuit schematic of the liquid crystal display device of 1st Embodiment. It is a figure which shows an example of the various voltage waveforms in the liquid crystal display device of 1st Embodiment. It is a schematic diagram which shows an example of the pixel structure of the liquid crystal display device of 1st Embodiment. It is a schematic diagram which shows the change of the brightness of the 1st, 2nd subpixel, polarity, and effective voltage in 2nd Embodiment of the liquid crystal display device by this invention, (a) is the brightness of 1st, 2nd subpixel, and It is a schematic diagram which shows the change of polarity, (b) is a schematic diagram which shows the change of the effective voltage applied to the liquid crystal layer of a 1st subpixel, (c) is a liquid crystal layer of a 2nd subpixel. It is a schematic diagram which shows the change of the applied effective voltage. It is a schematic diagram which shows the change of the subcapacitance voltage in the liquid crystal display device of 2nd Embodiment, and the initial auxiliary capacitance voltage in the vertical scanning period of each subpixel. It is a schematic diagram which shows the change of the brightness of the 1st, 2nd subpixel, polarity, and effective voltage in 3rd Embodiment of the liquid crystal display device by this invention, (a) is the brightness of 1st, 2nd subpixel, and It is a schematic diagram which shows the change of polarity, (b) is a schematic diagram which shows the change of the effective voltage applied to the liquid crystal layer of a 1st subpixel, (c) is a liquid crystal layer of a 2nd subpixel. It is a schematic diagram which shows the change of the applied effective voltage. It is a figure which shows an example of the various voltage waveforms in the liquid crystal display device of 3rd Embodiment. It is a schematic diagram which shows the change of the subcapacitance voltage in the liquid crystal display device of 3rd Embodiment, and the initial auxiliary capacitance voltage in the vertical scanning period of each subpixel. It is a schematic diagram which shows the change of the brightness of the 1st, 2nd subpixel, polarity, and effective voltage in 4th Embodiment of the liquid crystal display device by this invention, (a) is the brightness of the 1st, 2nd subpixel, and It is a schematic diagram which shows the change of polarity, (b) is a schematic diagram which shows the change of the effective voltage applied to the liquid crystal layer of a 1st subpixel, (c) is a liquid crystal layer of a 2nd subpixel. It is a schematic diagram which shows the change of the applied effective voltage. It is a schematic diagram which shows the change of the subcapacitance voltage in the liquid crystal display device of 4th Embodiment, and the initial auxiliary capacitance voltage in the vertical scanning period of each subpixel. It is a schematic diagram which shows the change of the brightness of the 1st, 2nd subpixel, polarity, and effective voltage in 5th Embodiment of the liquid crystal display device by this invention, (a) is the brightness of 1st, 2nd subpixel, and It is a schematic diagram which shows the change of polarity, (b) is a schematic diagram which shows the change of the effective voltage applied to the liquid crystal layer of a 1st subpixel, (c) is a liquid crystal layer of a 2nd subpixel. It is a schematic diagram which shows the change of the applied effective voltage. It is a figure which shows an example of the various voltage waveforms in the liquid crystal display device of 5th Embodiment. It is a schematic diagram which shows the change of the subcapacitance voltage in the liquid crystal display device of 5th Embodiment, and the auxiliary | assistant capacity voltage of the beginning in the vertical scanning period of each subpixel. It is a schematic diagram which shows the change of the brightness of the 1st, 2nd subpixel, polarity, and effective voltage in 6th Embodiment of the liquid crystal display device by this invention, (a) is the brightness of 1st, 2nd subpixel, and It is a schematic diagram which shows the change of polarity, (b) is a schematic diagram which shows the change of the effective voltage applied to the liquid crystal layer of a 1st subpixel, (c) is a liquid crystal layer of a 2nd subpixel. It is a schematic diagram which shows the change of the applied effective voltage. It is a schematic diagram which shows the change of the subcapacitance voltage of the subpixel in the liquid crystal display device of 6th Embodiment, and the initial auxiliary capacitance voltage in the vertical scanning period of each subpixel. It is a schematic diagram which shows the change of the brightness of the 1st, 2nd subpixel, polarity, and effective voltage in 7th Embodiment of the liquid crystal display device by this invention, (a) is the brightness of 1st, 2nd subpixel, and It is a schematic diagram which shows the change of polarity, (b) is a schematic diagram which shows the change of the effective voltage applied to the liquid crystal layer of a 1st subpixel, (c) is a liquid crystal layer of a 2nd subpixel. It is a schematic diagram which shows the change of the applied effective voltage. It is a schematic diagram which shows the change of the brightness and darkness and polarity of a subpixel in a certain frame of the liquid crystal display device of 7th Embodiment, and the initial auxiliary capacitance voltage in the vertical scanning period of each subpixel. It is a schematic diagram which shows the change of the light-darkness and polarity of a subpixel in the next flame | frame of the liquid crystal display device of 7th Embodiment, and the initial auxiliary capacitance voltage in the vertical scanning period of each subpixel. It is a figure which shows an example of the various voltage waveforms in the liquid crystal display device of 7th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pixel 10a, 10b Subpixel 13 Liquid crystal layer 17 Counter electrode 18a, 18b Subpixel electrode 100 Liquid crystal display device 100A Liquid crystal panel

(Embodiment 1)
A liquid crystal display device according to a first embodiment of the present invention will be described below with reference to the drawings.

  First, the configuration of the liquid crystal display device 100 of the present embodiment will be schematically described with reference to FIGS. FIG. 1 shows a liquid crystal display device 100 of this embodiment. As shown in FIG. 2, the liquid crystal panel 100 </ b> A of the liquid crystal display device 100 includes a display unit 110 having a plurality of pixels arranged in a matrix in a row direction and a column direction, and a drive circuit 120 that drives the display unit 110. And. Each pixel of the display unit 110 includes a liquid crystal layer and a plurality of electrodes that apply a voltage to the liquid crystal layer. The drive circuit 120 generates a drive signal based on the inputted input video signal.

  FIG. 3A is a schematic plan view of the electrode structure of one pixel, and FIG. 3B is a schematic cross-sectional view of one subpixel. FIG. 3B corresponds to a cross section taken along line 3B-3B ′ of FIG. As shown in FIG. 3A, one pixel 10 includes a first subpixel 10a and a second subpixel 10b arranged along the column direction. As shown in FIG. 3B, the first subpixel 10a includes a liquid crystal layer 13, a first subpixel electrode 18a, and a counter electrode 17 that faces the first subpixel electrode 18a through the liquid crystal layer 13. Have. 3B shows the configuration of the first subpixel 10a, the second subpixel 10b has the same configuration. The counter electrode 17 is typically one electrode common to all the pixels 10. In the liquid crystal display device 100 of the present embodiment, different voltages can be applied to the first subpixel electrode 18a and the second subpixel electrode 18b, whereby the effective voltage of the liquid crystal layer of the first subpixel 10a is changed to the second subpixel electrode 18b. It can be made different from the effective voltage of the liquid crystal layer of the pixel 10b.

  Next, referring to FIG. 4 to FIG. 6, while comparing with the liquid crystal display devices of Patent Literature 1 and Patent Literature 2, the brightness and darkness of the sub-pixels and the electric field direction (the lines of electric force lines) in the liquid crystal display device 100 of the present embodiment are compared. Change in orientation). Here, in order to simplify the description, it is assumed that a pixel displays a predetermined intermediate gradation over several frames.

  First, with reference to FIG. 4, changes in the brightness and electric field direction of the subpixels and changes in the effective voltage applied to the liquid crystal layers of the first and second subpixels in the liquid crystal display device of Patent Document 1 will be described. To do. In FIG. 4A, 1 to 6 indicate periods, and each period indicates a vertical scanning period. The “vertical scanning period” is defined as a period from when a scanning line for writing a display signal voltage is selected until the scanning line is selected for writing a next display signal voltage. To do. In addition, one frame period in the case of an input video signal for non-interlace driving and one field period in the case of an input video signal for interlace driving are referred to as “vertical scanning period of the input video signal”. Usually, one vertical scanning period in a liquid crystal display device corresponds to one vertical scanning period of an input video signal. In the following, for the sake of simplicity, a case where one vertical scanning period of the liquid crystal panel corresponds to one vertical scanning period of the input video signal will be described. However, the present invention is not limited to this, for example, one vertical scanning period of the input video signal. The present invention can also be applied to so-called double speed driving (vertical scanning frequency is 120 Hz) in which two vertical scanning periods (for example, 2 × 1/120 sec) of the liquid crystal panel are allocated to the scanning period (for example, 1/60 sec). Here, it is assumed that the lengths of the vertical scanning periods are equal. In each vertical scanning period, the difference (period) between the time when a certain scanning line is selected and the time when the next scanning line is selected is referred to as one horizontal scanning period (1H).

  In FIG. 4 (a), the upper and lower rectangles are the first and second subpixels, respectively. Of the first and second subpixels, the higher luminance subpixel is shown in white, and the Low subpixels are shown in black. In FIG. 4A, “+” and “−” indicate the polarities of the display signal voltage based on the common voltage supplied to the counter electrode when the corresponding scanning line is selected. Here, “+” indicates that the potential of the first subpixel electrode and the second subpixel electrode is higher than the potential of the counter electrode, and the electric field is directed from the subpixel electrode side to the counter electrode side. On the other hand, “-” indicates that the potential of the first subpixel electrode and the second subpixel electrode is lower than the potential of the counter electrode, and the electric field is directed from the counter electrode side to the subpixel electrode side. In the following description, “+” is also referred to as a first polarity, “−” is also referred to as a second polarity, and “+” and “−” are collectively referred to as a polarity. Further, a period that is “+” is also referred to as a first polarity period, and a period that is “−” is also referred to as a second polarity period.

  In the liquid crystal display device of Patent Document 1, as shown in FIG. 4A, periods 1, 3 and 5 are first polarity periods, periods 2, 4 and 6 are second polarity periods, and the polarity is vertical. Inverts every scanning period. As shown in FIG. 4A, in the liquid crystal display device of Patent Document 1, the luminance of the first subpixel is higher than the luminance of the second subpixel in all periods 1 to 6.

  4B and 4C, in the liquid crystal display device of Patent Document 1, the effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second subpixels in the vertical scanning periods are indicated by thick lines, respectively. Show. The effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second subpixels are effective values of the difference between the voltage of the first and second subpixel electrodes and the voltage Vc of the counter electrode. The voltage Vc is shown to be constant. Although not particularly shown in FIGS. 4B and 4C, as disclosed in Patent Document 1, the first and second subpixels are changed by changing the voltage of the auxiliary capacitance line. The voltage applied to the liquid crystal layer may be changed within the same vertical scanning period.

  In period 1, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is the second subpixel. Larger than the absolute value of the effective voltage applied to the liquid crystal layer (| VLspa |> | VLspb |). Therefore, as shown in FIG. 4A, the period 1 is the first polarity period, and the first subpixel is brighter than the second subpixel. When the period 1 shifts to the period 2, the effective voltages VLspa and VLspb applied to the liquid crystal layers of the first subpixel and the second subpixel change. In the period 2, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 4A, the period 2 is the second polarity period, and the first subpixel is brighter than the second subpixel.

  After period 3, the brightness and polarity of the first and second subpixels are the same as the brightness and polarity of the first and second subpixels in period 1 and period 2. In the liquid crystal display device of Patent Document 1, as shown in FIG. 4A, the luminance of the first subpixel is always higher than the luminance of the second subpixel, and the brightness of the subpixel is visually recognized, resulting in a rough display. Looks.

  Next, with reference to FIG. 5, changes in the brightness and electric field direction of the subpixels and changes in the effective voltage applied to the liquid crystal layers of the first and second subpixels in the liquid crystal display device of Patent Document 2 will be described. To do.

  As shown in FIG. 5A, also in the liquid crystal display device of Patent Document 2, the periods 1, 3 and 5 are the first polarity period, the periods 2, 4 and 6 are the second polarity period, and the polarity is vertical. Inverts every scanning period. In the liquid crystal display device of Patent Document 2, the luminance of the first subpixel is higher than the luminance of the second subpixel in the periods 1, 3, and 5, and the luminance of the second subpixel is the second luminance in the periods 2, 4, and 6. It is higher than the luminance of one subpixel.

  In FIG. 5B and FIG. 5C, the effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second sub-pixels in each vertical scanning period are indicated by bold lines. Although not particularly shown in FIGS. 5B and 5C, the first and second subpixels are changed by changing the voltage of the auxiliary capacitance line as disclosed in Patent Document 1. The voltage applied to the liquid crystal layer may be changed within the same vertical scanning period.

  In the period 1, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 5A, the period 1 is the first polarity period, and the first subpixel is brighter than the second subpixel. When shifting from the period 1 to the period 2, the effective voltages VLspa and VLspb of the liquid crystal layers of the first and second subpixels change. In the period 2, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 5A, the period 2 is the second polarity period, and the second subpixel is brighter than the first subpixel.

  After period 3, the brightness and polarity of the first and second subpixels are the same as the brightness and polarity of the first and second subpixels in period 1 and period 2. In the liquid crystal display device of Patent Document 2, the polarity is inverted every vertical scanning period and the brightness of the subpixel is inverted every vertical scanning period. Therefore, unlike the liquid crystal display device of Patent Document 1, the first subpixel is used. In addition, there is a period in which each of the second subpixels is brighter than the other, and as a result, display roughness can be suppressed. However, in the liquid crystal display device of Patent Document 2, a period in which the first subpixel is brighter than the second subpixel is always the first polarity period, and a period in which the second subpixel is brighter than the first subpixel is always present. Since it is the second polarity period, as understood from FIGS. 5B and 5C, the liquid crystal layer of the first sub-pixel over a plurality of vertical scanning periods (for example, periods 1 to 4). The average of the effective voltages VLspa is higher than the voltage Vc of the counter electrode, and the average of the effective voltages VLspb of the liquid crystal layer of the second subpixel over a plurality of vertical scanning periods (for example, periods 1 to 4) is It is lower than the voltage Vc. Therefore, in the liquid crystal display device of Patent Document 2, a bias of the direct current component (DC level) remains for each subpixel, and this bias causes a problem in reliability such as burn-in.

  Next, referring to FIG. 6, changes in the brightness of the subpixels and changes in the direction of the electric field, and changes in the effective voltage applied to the liquid crystal layers of the first and second subpixels in the liquid crystal display device 100 of the present embodiment. explain.

  As shown in FIG. 6A, in the liquid crystal display device 100 of the present embodiment, periods 1, 2, 5, and 6 are first polarity periods, and periods 3 and 4 are second polarity periods. As described above, the first polarity period is a period in which the voltage of the first and second subpixel electrodes is higher than the voltage of the counter electrode, and the voltage of the first and second subpixel electrodes is in the second polarity period. This is a period lower than the voltage of the counter electrode. Here, looking at four consecutive vertical scanning periods, of the four vertical scanning periods, two are first polarity periods and the remaining two are second polarity periods. For example, in the periods 1 to 4 in FIG. 6A, the period 1 and the period 2 are the first polarity period, and the period 3 and the period 4 are the second polarity period.

  In FIG. 6B and FIG. 6C, the effective voltages VLspa and VLspb in each vertical scanning period applied to the liquid crystal layers of the first and second subpixels are indicated by bold lines, respectively. In the present embodiment as well, as disclosed in Patent Document 1 and Patent Document 2, the voltage of the auxiliary capacitance wiring is changed and applied to the liquid crystal layers of the first and second subpixels. The voltage may be changed within the same vertical scanning period. 6B and 6C are based on the voltage Vc of the counter electrode, the voltage Vc of the counter electrode is shown to be constant regardless of time. The voltage Vc may change according to time.

  In the period 1, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Accordingly, as shown in FIG. 6A, the period 1 is the first polarity period, and the first subpixel is brighter than the second subpixel.

  When shifting from the period 1 to the period 2, the effective voltages VLspa and VLspb of the liquid crystal layers of the first and second subpixels change. In the period 2, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 6A, the period 2 is the first polarity period, and the second subpixel is brighter than the first subpixel.

  In the period 3, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 6A, the period 3 is the second polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 4, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Accordingly, as shown in FIG. 6A, the period 4 is the second polarity period, and the second subpixel is brighter than the first subpixel. Hereinafter, after the period 5, the contrast and polarity of the first and second sub-pixels are the same as those of the first and second sub-pixels during the periods 1 to 4.

  As described above, in the liquid crystal display device 100 of the present embodiment, two vertical scanning periods among the four consecutive vertical scanning periods are the first polarity periods. Among them, one is a vertical scanning period that satisfies | VLspa |> | VLspb | (for example, period 1), and the other is a vertical scanning period that satisfies | VLspa | <| VLspb | (for example, period 2). The remaining two of the four consecutive vertical scanning periods are the second polarity period. Among these, one is a vertical scanning period that satisfies | VLspa |> | VLspb | (for example, period 3), and the other is a vertical scanning period that satisfies | VLspa | <| VLspb | (for example, period 4). As understood from FIG. 6A, in the liquid crystal display device 100 of this embodiment, the brightness of the sub-pixel is inverted every vertical scanning period, and the polarity is inverted every two vertical scanning periods. The (brightness, polarity) of one subpixel changes in order of (bright, +), (dark, +), (bright,-), (dark,-), and the (brightness and darkness) of the second subpixel. , Polarity) change in the order of (dark, +), (bright, +), (dark,-), (bright,-). Here, “bright” indicates lighter than the other subpixel, and “dark” indicates darker than the other subpixel. By changing the effective voltage of the subpixel in this way, the average value of the effective voltage applied to the liquid crystal layer of the first subpixel and the liquid crystal layer of the second subpixel in each of the first polarity period and the second polarity period. The difference from the average value of the effective voltage applied to is substantially zero.

  In the liquid crystal display device 100 of the present embodiment, unlike the liquid crystal display device of Patent Document 1, the brightness of the sub-pixels is inverted every vertical scanning period, so that display roughness can be suppressed. Further, in the liquid crystal display device 100 of the present embodiment, unlike the liquid crystal display device of Patent Document 2, both the first polarity period and the second polarity period satisfy (| VLspa |> | VLspb |), | VLspa | <| VLspb |), and as understood from FIGS. 6 (b) and 6 (c), a plurality of vertical scanning periods (for example, periods 1 to 4) are used. Both the average of the effective voltage VLspa and the average of the effective voltage VLspb can be made zero. Further, even if the average of the effective voltages VLspa and VLspb is not zero, the average of the effective voltage VLspa and the average of the effective voltage VLspb are almost equal. Therefore, by adjusting the counter voltage, the average of the effective voltages VLspa and VLspb Both can be adjusted to zero. Thus, by making the average effective voltage zero, occurrence of reliability problems such as burn-in can be suppressed. There may be various configurations for applying different voltages to the liquid crystal layers of the first and second subpixels so as to satisfy the above relationship.

  The present embodiment is preferably applied to a liquid crystal display device using a vertical alignment type liquid crystal layer including a nematic liquid crystal material having negative dielectric anisotropy. In particular, it is preferable that the liquid crystal layer included in each sub-pixel includes four domains whose azimuth directions in which liquid crystal molecules tilt when a voltage is applied differ from each other by about 90 ° (MVA mode). Alternatively, the liquid crystal layer included in each sub-pixel may be a liquid crystal layer that has an axially symmetric orientation at least when a voltage is applied (ASM mode).

  Hereinafter, the MVA mode liquid crystal display device 100 according to the present embodiment will be described in more detail.

  As shown in FIG. 1, the liquid crystal display device 100 includes a liquid crystal panel 100A, phase difference compensation elements (typically phase difference compensation plates) 20a and 20b provided on both sides of the liquid crystal panel 100A, and sandwiching them. Polarizing plates 30 a and 30 b and a backlight 40. The transmission axes (also referred to as “polarization axes”) of the polarizing plates 30a and 30b are arranged so as to be orthogonal to each other (crossed Nicols arrangement), and are formed on the liquid crystal layer 13 (see FIG. 3B) of the liquid crystal panel 100A. Black display is performed in a state where no voltage is applied (vertical alignment state). Therefore, the liquid crystal display device 100 is a normally black mode liquid crystal display device. The phase difference compensation elements 20a and 20b are provided to improve the viewing angle characteristics of the liquid crystal display device, and are optimally designed using known techniques. Specifically, in the black display state, optimization is performed so that the difference in luminance (black luminance) between oblique observation and front observation in all azimuth directions is minimized.

  As shown in FIG. 3A, the scanning line 12 is disposed between the first subpixel electrode 18a and the second subpixel electrode 18b. Of course, on the substrate 11a, in order to apply a predetermined voltage to each of the first and second subpixel electrodes 18a and 18b at a predetermined timing, the scanning line 12, the signal line, and the TFT ( Further, a circuit for driving them is formed. The other substrate 11b is provided with a color filter or the like as necessary.

  Next, the structure of one pixel in the MVA mode liquid crystal display device 100 will be described with reference to FIGS. 3 (a) and 3 (b). The basic configuration and operation of the MVA mode liquid crystal display device are disclosed in, for example, Japanese Patent Application Laid-Open No. 11-242225.

  As shown in FIG. 3B, the subpixel electrode 18a formed on the glass substrate 11a is provided with a slit 18s, and the subpixel electrode 18a and the counter electrode 17 cause an oblique electric field in the liquid crystal layer 13. Is generated. A rib 19 protruding toward the liquid crystal layer 13 is provided on the surface of the glass substrate 11b on which the counter electrode 17 is provided. The liquid crystal layer 13 is made of a nematic liquid crystal material having negative dielectric anisotropy, and is a vertical alignment film (not shown) formed so as to cover the counter electrode 17, the rib 19, and the subpixel electrodes 18a and 18b. Thus, a substantially vertical alignment state is obtained when no voltage is applied. The vertically aligned liquid crystal molecules can be stably tilted in a predetermined direction by the surface (inclined side surface) of the rib 19 and the oblique electric field.

  As shown in FIG. 3B, the rib 19 is inclined in a mountain shape toward the center of the rib, and the liquid crystal molecules are aligned substantially perpendicular to the inclined surface. Therefore, the rib 19 generates a distribution of tilt angles of liquid crystal molecules (an angle formed between the substrate surface and the long axis of the liquid crystal molecules). The slits 18s regularly change the direction of the electric field applied to the liquid crystal layer. As a result, the orientation of the liquid crystal molecules during the application of an electric field by the action of the ribs 19 and the slits 18s is oriented in the directions of the arrows shown in FIG. Therefore, it is possible to obtain a good viewing angle characteristic having symmetrical characteristics in the vertical and horizontal directions. The rectangular display surface of the liquid crystal panel 100A is typically arranged with the longitudinal direction in the horizontal direction, and the transmission axis of the polarizing plate 30a is set parallel to the longitudinal direction. On the other hand, the pixels 10 are arranged in a direction in which the longitudinal direction of the pixels 10 is orthogonal to the longitudinal direction of the liquid crystal panel 100A.

  As shown in FIG. 3A, the first subpixel 10a and the second subpixel 10b have the same area, and in each subpixel, the first rib extending in the first direction and the first direction are substantially orthogonal to each other. A second rib extending in the second direction, and the first rib and the second rib are arranged symmetrically with respect to a center line parallel to the scanning line 12 in each subpixel, It is preferable that the rib arrangement in the sub-pixel and the rib arrangement in the other sub-pixel are symmetrical with respect to the center line orthogonal to the scanning line 12. With such an arrangement, the liquid crystal molecules in each subpixel are aligned in the four directions of upper right, upper left, lower left, and lower right, and the entire pixel including the first subpixel and the second subpixel, Since the areas of the respective liquid crystal domains are substantially the same, it is possible to obtain good viewing angle characteristics having symmetrical characteristics in the vertical and horizontal directions. This effect is remarkable when the area of the pixel is small. Furthermore, it is preferable to employ a configuration in which the interval between the center lines parallel to the scanning lines in each sub-pixel is equal to about one half of the arrangement pitch of the scanning lines.

  Next, referring to FIGS. 7 to 9, the specific structure of one pixel 10 in the liquid crystal display device 100 of the present embodiment, and the liquid crystal layers of the two subpixels 10 a and 10 b included in the pixel 10. A description will be given of applying a different voltage to.

  As shown in FIG. 7, the pixel 10 has two sub-pixels 10a and 10b. The sub-pixel electrodes 18a and 18b of the sub-pixels 10a and 10b are respectively provided with a TFT 16a, a TFT 16b, and a storage capacitor (CS). 22a and 22b are connected. The gate electrodes of the TFTs 16 a and 16 b are connected to the scanning line 12, and the source electrodes are connected to a common (same) signal line 14. The auxiliary capacitors 22a and 22b are connected to an auxiliary capacitor line (CS bus line) 24a and an auxiliary capacitor line 24b, respectively. The auxiliary capacitors 22a and 22b are provided between the auxiliary capacitor electrode electrically connected to the sub-pixel electrodes 18a and 18b, the auxiliary capacitor counter electrode electrically connected to the auxiliary capacitor wires 24a and 24b, respectively. The insulating layer (not shown) is formed. The storage capacitor counter electrodes of the storage capacitors 22a and 22b are independent from each other, and different storage capacitor counter voltages can be supplied from the storage capacitor lines 24a and 24b, respectively.

  FIG. 8 shows an equivalent circuit of one pixel 10 in the liquid crystal display device 100. In this equivalent circuit, the liquid crystal layers of the respective subpixels 10a and 10b are represented as liquid crystal layers 13a and 13b. The liquid crystal capacitance formed by the subpixel electrodes 18a and 18b, the liquid crystal layers 13a and 13b, and the counter electrode 17 (common to the subpixels 10a and 10b) is represented as Clca and Clcb. The capacitance values of the liquid crystal capacitors Clca and Clcb are CLC (V), and the value of CLC (V) depends on the effective voltage (V) applied to the liquid crystal layers of the sub-pixels 10a and 10b. The auxiliary capacitors 22a and 22b that are independently connected to the liquid crystal capacitors of the sub-pixels 10a and 10b are represented as Ccsa and Ccsb, respectively, and the capacitance values are the same value CCS.

  In the first subpixel 10a, one electrode of each of the liquid crystal capacitor Clca and the auxiliary capacitor Ccsa is connected to the drain electrode of the TFT 16a functioning as a switching element of the subpixel 10a, and the other electrode of the liquid crystal capacitor Clca is a counter electrode. 17 and the other electrode of the auxiliary capacitor Ccsa is connected to the auxiliary capacitor line 24a. In the second subpixel 10b, one electrode of each of the liquid crystal capacitor Clcb and the auxiliary capacitor Ccsb is connected to the drain electrode of the TFT 16b functioning as a switching element of the subpixel 10b, and the other electrode of the liquid crystal capacitor Clcb is The other electrode of the auxiliary capacitor Ccsb is connected to the counter electrode 17 and is connected to the auxiliary capacitor line 24b. The gate electrodes of the TFTs 16 a and 16 b are both connected to the scanning line 12, and the source electrodes are both connected to the signal line 14.

  FIG. 9 schematically shows changes in each voltage for driving the liquid crystal display device 100 of the present embodiment within a certain vertical scanning period. In FIG. 9, Vs indicates the voltage of the signal line 14, Vcsa indicates the voltage of the auxiliary capacitance wiring 24a, Vcsb indicates the voltage of the auxiliary capacitance wiring 24b, Vg indicates the voltage of the scanning line 12, and Vlca is the first voltage. The voltage of the subpixel electrode 18a is indicated, and Vlcb indicates the voltage of the second subpixel electrode 18b. Moreover, the broken line in the figure indicates the voltage COMMON (Vc) of the counter electrode 17. The voltage Vcsa of the auxiliary capacitance line 24a periodically changes in the range from Vc−Vad to Vc + Vad, and the voltage Vcsb of the auxiliary capacitance line 24b also changes periodically in the range from Vc−Vad to Vc + Vad. The voltage Vcsb of the auxiliary capacitance line 24b has a waveform that is 180 degrees out of phase with the voltage Vcsa of the auxiliary capacitance line 24a.

  The operation of the equivalent circuit shown in FIG. 8 will be described below with reference to FIG.

  At time T1, the voltage Vg of the scanning line 12 changes from VgL to VgH, so that the TFT 16a and the TFT 16b are simultaneously turned on (on state), and the signal line 14 is connected to the subpixel electrodes 18a and 18b of the subpixels 10a and 10b. The voltage Vs is transmitted, and the liquid crystal capacitors Clca and Clcb of the sub-pixels 10a and 10b are charged. Similarly, the auxiliary capacitors Ccsa and Ccsb of the respective sub-pixels are charged from the signal line 14.

Next, when the voltage Vg of the scanning line 12 changes from VgH to VgL at time T2, the TFTs 16a and 16b are turned off at the same time (off state), and the liquid crystal capacitors Clca and Clcb of the sub-pixels 10a and 10b are added. The capacitors Ccsa and Ccsb are both electrically insulated from the signal line 14. Immediately after this, due to the pull-in phenomenon due to the influence of the parasitic capacitances of the TFTs 16a and 16b, the voltages Vlca and Vlcb of the first and second subpixel electrodes 18a and 18b are lowered by substantially the same voltage Vd,
Vlca = Vs−Vd
Vlcb = Vs−Vd
It becomes. At this time, the voltages Vcsa and Vcsb of the respective auxiliary capacitance lines are Vcsa = Vc−Vad
Vcsb = Vc + Vad
It is.

At time T3, the voltage Vcsa of the auxiliary capacitance line 24a connected to the auxiliary capacitance Ccsa increases by 2 × Vad from Vc−Vad to Vc + Vad, and the voltage Vcsb of the auxiliary capacitance line 24b connected to the auxiliary capacitance Ccsb is from Vc + Vad. Decrease by 2 × Vad to Vc−Vad. As the auxiliary capacitance lines 24a and 24b change in voltage, the voltages Vlca and Vlcb of the first and second subpixel electrodes are respectively
Vlca = Vs−Vd + 2 × K × Vad
Vlcb = Vs−Vd−2 × K × Vad
To change. However, K = CCS / (CLC (V) + CCS).

At time T4, the voltage Vcsa of the auxiliary capacitance line 24a changes from Vc + Vad to Vc−Vad, and the voltage Vcsb of the auxiliary capacitance line 24b changes from Vc−Vad to Vc + Vad by 2 × Vad. The subpixel electrode voltages Vlca and Vlcb are
Vlca = Vs−Vd + 2 × K × Vad
Vlcb = Vs−Vd−2 × K × Vad
From
Vlca = Vs−Vd
Vlcb = Vs−Vd
To change.

At time T5, the voltage Vcsa of the auxiliary capacitance line 24a changes from Vc−Vad to Vc + Vad, the voltage Vcsb of the auxiliary capacitance line 24b changes from Vc + Vad to Vc−Vad by 2 × Vad, and the first and second subpixel electrodes The voltages Vlca and Vlcb of
Vlca = Vs−Vd
Vlcb = Vs−Vd
From
Vlca = Vs−Vd + 2 × K × Vad
Vlcb = Vs−Vd−2 × K × Vad
To change.

Vcsa, Vcsb, Vlca, and Vlcb alternately repeat the changes in T4 and T5 at intervals of an integral multiple of the horizontal scanning time 1H. Whether the repetition interval of T4 and T5 is set to 1 time, 1 time, 2 times, 3 times, or more than 1H depends on the driving method (polarity inversion method, etc.) of the liquid crystal display device and the display state ( It may be set as appropriate in consideration of flickering, display roughness, and the like. This repetition is continued when the pixel 10 is next rewritten, that is, until a time equivalent to T1 is reached. Accordingly, the average voltages Vlca and Vlcb of the first and second subpixel electrodes are respectively
Vlca = Vs−Vd + K × Vad
Vlcb = Vs−Vd−K × Vad
It becomes.

Therefore, the effective voltages V1 (= VLspa) and V2 (= VLspb) applied to the liquid crystal layers 13a and 13b of the subpixels 10a and 10b are respectively the voltages of the first subpixel electrode 18a and the counter electrode 17. The difference between the voltage of the second subpixel electrode 18b and the voltage of the counter electrode 17, that is,
V1 = VLspa = Vlca-Vcom
V2 = VLspb = Vlcb-Vcom
That is,
V1 = Vs−Vd + K × Vad−Vc
V2 = Vs−Vd−K × Vad−Vc
It becomes. Therefore, the difference ΔV (= V1−V2) in effective voltage applied to the liquid crystal layers 13a and 13b of the sub-pixels 10a and 10b is ΔV = 2 × K × Vad (where K = CCS / (CLC (V ) + CCS)), and different voltages can be applied to the liquid crystal layers 13a and 13b.

  FIG. 10 schematically shows the relationship between V1 and V2 in the liquid crystal display device 100 of the present embodiment. As understood from FIG. 10, in the liquid crystal display device 100 of the present embodiment, the value of ΔV increases as the value of V1 decreases. The reason why the value of ΔV changes depending on V1 or V2 is that the capacitance value CLC (V) of the liquid crystal capacitance changes depending on the voltage.

  FIG. 11A shows the γ characteristic at the right 60 ° viewing angle in the liquid crystal display device 100 of the present embodiment, and FIG. 11B shows the γ characteristic at the upper right 60 ° viewing angle in the liquid crystal display device 100 of the present embodiment. The γ characteristic is shown. FIGS. 11A and 11B also show γ characteristics when the same voltage is applied to the sub-pixels 10a and 10b for comparison. As understood from FIG. 11A and FIG. 11B, the gradation characteristics of the liquid crystal display device 100 of the present embodiment are in the vertical axis as compared with the case where the voltages of the two subpixel electrodes are equal. The value is closer to the gradation characteristic (γ = 2.2) in the front direction, which is the value on the horizontal axis, and the γ characteristic is improved. As described above, by changing each voltage as shown in FIG. 9 within one vertical scanning period, different effective voltages can be applied to the liquid crystal layers of different sub-pixels. The gamma characteristic when observed from can be improved.

  Hereinafter, with reference to FIG. 12, a change over a plurality of vertical scanning periods of a voltage applied to one pixel 10 described with reference to FIGS. 7 and 8 will be described.

  In FIG. 12, Vg indicates the voltage of the scanning line 12, Vcsa indicates the voltage of the first auxiliary capacitance line 24a, Vcsb indicates the voltage of the second auxiliary capacitance line 24b, and VLspa indicates the liquid crystal layer of the first subpixel 10a. The effective voltage applied to 13a is shown, and VLspb shows the effective voltage applied to the liquid crystal layer 13b of the second subpixel 10b. As described above, the vertical scanning period is a period from when a certain scanning line is selected until the next scanning line is selected. In FIG. 12, this period is indicated by V-Total. Note that FIG. 12 does not show a change in the voltage Vd caused by the pulling phenomenon described with reference to FIG.

  The voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines have a display period AH and an adjustment period BH. The voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines periodically change with a period (20H in this case) in the display period AH as one period, and a period different from the period of the display period AH in the adjustment period BH. (In this case, 36H or 26H), one cycle is changed. The sum of the display period AH and the adjustment period BH is equal to the vertical scanning period (V-Total). Here, the display period AH starts when the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines change after the start of the vertical scanning period corresponding to a certain frame, and the adjustment period BH After the vertical scanning period corresponding to the frame is finished, the process is finished when the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines are changed. In the present embodiment, the frame frequency is, for example, 60 Hz.

  FIG. 12 shows changes in voltage during four vertical scanning periods. In the following description, the four vertical scanning periods are referred to as first to fourth vertical scanning periods, respectively, and the display period AH and the adjustment period BH corresponding to each vertical scanning period are respectively referred to as the first to fourth display periods AH, This is referred to as the first to fourth adjustment periods BH. Also here, when the voltage Vcsa of the auxiliary capacitance line 24a changes to a higher voltage (VcH), the voltage Vcsb of the auxiliary capacitance line 24b changes to a lower voltage (VcL), and conversely, Vcsa becomes a lower voltage (Vcsa). When changing to VcL), Vcsb changes to a higher voltage (VcH). The difference between VcH and VcL corresponds to 2 × Vad described with reference to FIG.

  At the time when the voltage Vcsa of the first auxiliary capacitance line 24a is VcL and the voltage Vcsb of the second auxiliary capacitance line 24b is VcH, the voltage Vg of the scanning line 12 changes from VgL to VgH. As the voltage Vg of the scanning line 12 changes to VgH, the first vertical scanning period starts and the first and second subpixel electrodes 18a and 18b are charged. Since the voltage Vs of the signal line 14 is higher than the voltage Vc of the counter electrode 17 while the voltage Vg of the scanning line 12 is VgH, the voltages of the first subpixel electrode 18a and the second subpixel electrode 18b are charged as a result of charging. It becomes higher than the voltage Vc of the counter electrode 17. Thereafter, when the voltage Vg of the scanning line 12 returns from VgH to VgL again, the charging of the first and second subpixel electrodes 18a and 18b ends.

  Thereafter, the voltage Vcsa of the first auxiliary capacitance line 24a increases to VcH, and the voltage Vcsb of the second auxiliary capacitance line 24b decreases to VcL. Here, the first display period AH starts when the voltage Vcsa of the first auxiliary capacitance line 24a increases and the voltage Vcsb of the second auxiliary capacitance line 24b decreases. In the first display period AH, the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b increase or decrease every 10H and periodically change with 20H as one cycle. When the first display period AH ends, the first adjustment period BH starts. In the first adjustment period BH, the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b increase or decrease at 18H. Since the voltages of the first and second subpixel electrodes 18a and 18b change according to changes in the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b, the first subpixel 10a is changed in the first vertical scanning period. The absolute value of the effective voltage applied to the liquid crystal layer 13a is larger than the absolute value of the effective voltage applied to the liquid crystal layer 13b of the second subpixel 10b, and the first subpixel 10a is larger than the second subpixel 10b. It becomes brighter.

  In the first adjustment period BH, the voltage Vg of the scanning line 12 changes from VgL to VgH at the time when the voltage Vcsa of the first auxiliary capacitance line 24a is VcH and the voltage Vcsb of the second auxiliary capacitance line 24b is VcL. . As the voltage Vg of the scanning line 12 changes to VgH, the first vertical scanning period ends and the second vertical scanning period starts, and the first and second subpixel electrodes 18a and 18b are charged. Is called. Since the voltage Vs of the signal line 14 is higher than the voltage Vc of the counter electrode 17 while the voltage Vg of the scanning line 12 is VgH, the voltages of the first subpixel electrode 18a and the second subpixel electrode 18b are charged as a result of charging. It becomes higher than the voltage Vc of the counter electrode 17. Thereafter, when the voltage Vg of the scanning line 12 returns from VgH to VgL again, the charging of the first and second subpixel electrodes 18a and 18b ends.

  Thereafter, the voltage Vcsa of the first auxiliary capacitance line 24a decreases to VcL, and the voltage Vcsb of the second auxiliary capacitance line 24b increases to VcH. When the voltage Vcsa of the first auxiliary capacitance line 24a decreases and the voltage Vcsb of the second auxiliary capacitance line 24b increases, the first adjustment period ends and the second display period AH starts. Also in the second display period AH, the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b increase or decrease every 10H and periodically change with 20H as one cycle, and in the second adjustment period BH The voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b increase or decrease at 13H. Since the voltages of the first and second subpixel electrodes 18a and 18b change according to changes in the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b, the second subpixel 10b is changed in the second vertical scanning period. The absolute value of the effective voltage applied to the liquid crystal layer 13b is larger than the absolute value of the effective voltage applied to the liquid crystal layer 13a of the first subpixel 10a, and the second subpixel 10b is larger than the first subpixel 10a. It becomes brighter.

  Next, the voltage Vg of the scanning line 12 is changed from VgL to VgH at the time when the voltage Vcsa of the first auxiliary capacitance line 24a is VcH and the voltage Vcsb of the second auxiliary capacitance line 24b is VcL in the second adjustment period BH. Change. As the voltage Vg of the scanning line 12 changes to VgH, the second vertical scanning period ends and the third vertical scanning period starts, and the first and second subpixel electrodes 18a and 18b are charged. Is called. Since the voltage Vs of the signal line 14 is lower than the voltage Vc of the counter electrode 17 while the voltage Vg of the scanning line 12 is VgH, the voltages of the first subpixel electrode 18a and the second subpixel electrode 18b are charged as a result of charging. It becomes lower than the voltage Vc of the counter electrode 17. Thereafter, when the voltage Vg of the scanning line 12 returns from VgH to VgL again, the charging of the first and second subpixel electrodes 18a and 18b ends.

  Thereafter, the voltage Vcsa of the first auxiliary capacitance line 24a decreases to VcL, and the voltage Vcsb of the second auxiliary capacitance line 24b increases to VcH. When the voltage Vcsa of the first auxiliary capacitance line 24a decreases and the voltage Vcsb of the second auxiliary capacitance line 24b increases, the second adjustment period BH ends and the third display period AH starts. In the third display period AH, the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b increase or decrease every 10H and periodically change with 20H as one cycle. In the third adjustment period BH, The voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b increase or decrease at 18H. Since the voltages of the first and second subpixel electrodes 18a and 18b change according to changes in the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b, the first subpixel 10a is changed in the third vertical scanning period. The absolute value of the effective voltage applied to the liquid crystal layer 13a is larger than the absolute value of the effective voltage applied to the liquid crystal layer 13b of the second subpixel 10b, and the first subpixel 10a is larger than the second subpixel 10b. It becomes brighter.

  Next, the voltage Vg of the scanning line 12 is changed from VgL to VgH at the time when the voltage Vcsa of the first auxiliary capacitance line 24a is VcL and the voltage Vcsb of the second auxiliary capacitance line 24b is VcH in the third adjustment period BH. Change. As the voltage Vg of the scanning line 12 changes to VgH, the third vertical scanning period ends and the fourth vertical scanning period starts, and the first and second subpixel electrodes 18a and 18b are charged. Is called. Since the voltage Vs of the signal line 14 is lower than the voltage Vc of the counter electrode 17 while the voltage Vg of the scanning line 12 is VgH, the voltages of the first subpixel electrode 18a and the second subpixel electrode 18b are charged as a result of charging. It becomes lower than the voltage Vc of the counter electrode 17. Thereafter, when the voltage Vg of the scanning line 12 returns from VgH to VgL again, the charging of the first and second subpixel electrodes 18a and 18b ends.

  Thereafter, the voltage Vcsa of the first auxiliary capacitance line 24a increases to VcH, and the voltage Vcsb of the second auxiliary capacitance line 24b decreases to VcL. When the voltage Vcsa of the first auxiliary capacitance line 24a increases and the voltage Vcsb of the second auxiliary capacitance line 24b decreases, the third adjustment period BH ends and the fourth display period AH starts. In the fourth display period AH, the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b increase or decrease every 10H and periodically change with 20H as one cycle. In the fourth adjustment period BH, The voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b increase or decrease at 13H. Since the voltages of the first and second subpixel electrodes 18a and 18b change according to the change of the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines 24a and 24b, the second subpixel 10b in the fourth vertical scanning period. The absolute value of the effective voltage applied to the liquid crystal layer 13b is larger than the absolute value of the effective voltage applied to the liquid crystal layer 13a of the first subpixel 10a, and the second subpixel 10b is larger than the first subpixel 10a. It becomes brighter. After the fifth vertical scanning period, each voltage changes similarly to the first to fourth vertical scanning periods shown in FIG.

  As described above, (brightness, polarity) of the first subpixel changes in order of (bright, +), (dark, +), (bright,-), (dark,-), and the second The subpixel (brightness, polarity, polarity) changes in the order of (darkness, +), (brightness, +), (darkness,-), (brightness,-), and the lightness and polarity of the first and second subpixels. Changes as shown in FIG. In this way, by changing the voltages Vcsa and Vcsb of the first and second auxiliary capacitance lines, it is possible to suppress deterioration in display quality in the liquid crystal display device in which the viewing angle dependency of the γ characteristic is improved.

  As described so far, in the liquid crystal display device according to the present embodiment, the magnitude relationship between the potentials of the pixel electrode and the counter electrode is reversed at regular intervals, and the direction of the electric field applied to the liquid crystal layer is constant. It is set to invert every time. In this case, in a typical liquid crystal display device in which the counter electrode and the pixel electrode are provided on different substrates, the direction of the electric field applied to the liquid crystal layer is reversed from the light source side to the observer side and from the observer side to the light source side. . As described above, setting the voltage to be an AC voltage is called an “AC driving method”. In the liquid crystal display device of the present embodiment, the period of inversion of the direction of the electric field applied to the liquid crystal layer is twice (for example, 66.667 ms) two frame periods (for example, 33.333 ms). That is, in the liquid crystal display device of this embodiment, the direction of the electric field applied to the liquid crystal layer is reversed for every two frame images to be displayed. Therefore, when displaying a still image, if the electric field strength (applied voltage) does not exactly match the direction of each electric field, that is, the electric field strength changes every time the electric field direction changes, As the intensity changes, the luminance of the pixel changes, causing a problem that the display flickers.

  In order to prevent this flickering, it is necessary to make the electric field strengths (applied voltages) in the directions of the respective electric fields exactly match. However, in an industrially produced liquid crystal display device, it is difficult to accurately match the electric field strength for each electric field direction, and therefore pixels having different electric field directions are adjacent to each other in the display region. The flickering is reduced by arranging and utilizing the effect of spatially averaging the luminance of the pixels. This method is generally called “dot inversion” or “line inversion”. In addition, in these “inversion driving”, the pixel cycle to be inverted is a checkered pattern inversion (polarity inversion for each row and column) in units of one pixel (one dot inversion), or one line There are various forms, such as polarity inversion every two rows and every column (two rows and one column dot inversion), as well as those inversion (inversion every row) (one line inversion). Is set.

  From the above, in order to prevent flickering, it is preferable to satisfy the following three conditions.

  The first condition is to make the absolute value of the effective voltage applied to the liquid crystal layer match as much as possible in each electric field direction (polarity of each applied voltage). That is, as in the case of the above-described reliability problem, the average value of the voltage applied to the liquid crystal layer is to be as close to zero as possible.

  The second condition is that pixels having different directions of the electric field applied to the liquid crystal layer are arranged adjacent to each other in each frame period.

  The third condition is that subpixels brighter than the other subpixel are arranged as randomly as possible in the same frame. The most preferable display is that subpixels brighter than the other subpixel are not adjacent to each other in the column and row directions, in other words, subpixels brighter than the other subpixel are arranged in a checkered pattern. It is to be.

  Hereinafter, it will be described that the liquid crystal display device of the present embodiment satisfies the above three conditions. Prior to explaining that the three conditions are specifically satisfied, referring to FIG. 13 and FIG. 14, the liquid crystal display device 100 of the present embodiment has a pixel arrangement suitable for 1-dot inversion driving that satisfies the above conditions. Explain that it has.

  FIG. 13 shows an equivalent circuit of the liquid crystal display device 100. In FIG. 13, each pixel has the structure shown in FIGS. The pixels are arranged in a matrix. In the following description, a pixel in the nth row and mth column is referred to as a pixel nm, and two subpixels included in the pixel nm are referred to as a subpixel nma. , Nm-B.

  The liquid crystal display device 100 is provided with ten auxiliary capacity trunk lines CS1 to CS10, and each subpixel is connected to any one of the auxiliary capacity main lines CS1 to CS10 via an auxiliary capacity line (CS bus line). Has been. For example, the storage capacitor main line CS2 includes sub-pixels 1-a-B, 1-b-B, 1-c-B,... In the first pixel row and sub-pixels 2-a-A, 2 in the second pixel row. -B-A, 2-c-A, etc., and a certain subpixel is connected to the same auxiliary capacitance trunk line via the same auxiliary capacitance line as a subpixel included in another pixel adjacent to the subpixel. It is connected to the.

  Here, the configuration of the first and second sub-pixels 1-a-A and 1-a-B included in the pixel 1-a specified by the scanning line G1 and the signal line Sa will be described. The first and second subpixels 1-a-A and 1-a-B have liquid crystal capacitors CLC1-a-A and CLC1-a-B, and auxiliary capacitors CCS1-a-A and CCS1-a-B. is doing. The liquid crystal capacitor includes a sub-pixel electrode, a counter electrode ComLC, and a liquid crystal layer provided therebetween. The auxiliary capacitor includes an auxiliary capacitor electrode, an insulating film, and an auxiliary capacitor counter electrode (ComCS1, ComCS2). It consists of and.

  The first and second subpixels 1-a-A and 1-a-B are connected to a common signal line Sa via the corresponding TFT 1-a-A and TFT 1-a-B, respectively. The TFT 1-a-A and the TFT 1-a-B are on / off controlled by the voltage supplied to the common scanning line G1, and when the two TFTs are in the on state, the first and second subpixels 1- A voltage is supplied from the common signal line Sa to the subpixel electrode and the auxiliary capacitance electrode included in each of aA and 1-aB. The auxiliary capacity counter electrode of the subpixel 1-a-A is connected to the auxiliary capacity main line CS1 via the auxiliary capacity line (CS bus line) CS1, and the auxiliary capacity counter electrode of the subpixel 1-a-B is connected to the auxiliary capacity. The storage capacitor main line CS2 is connected via a wiring (CS bus line) CS2. As described above, the configuration shown in FIG. 13 is a configuration in which one sub-capacitance wiring or one scanning line is shared by two subpixels, and has the advantage that the aperture ratio of the pixel can be increased. Yes.

  FIG. 14 shows the contrast and polarity of the sub-pixels changed within the effective scanning period of a certain frame. FIG. 14 illustrates pixels in the first to twelfth rows and the af columns. FIG. 15 shows waveforms of various voltages (signals) for driving the liquid crystal display device having the configuration shown in FIG. In FIG. 15, Vsa indicates the voltage of the signal line Sa, Vsb indicates the voltage of the signal line Sb, Vg1 to Vg12 indicate the voltages of the scanning lines G1 to G12, and Vcs1 to Vcs10 are the voltages of the auxiliary capacity trunk lines CS1 to CS10. VLsp1-aA to VLsp2-b-B indicate effective voltages applied to the liquid crystal layer of the corresponding subpixel. FIG. 15 shows a voltage waveform in one vertical scanning period.

  The liquid crystal display device having the configuration of FIG. 13 is driven by a voltage having the waveform shown in FIG. In the following description, it is assumed that all pixels display the same halftone to avoid overcomplicating the description. When all the pixels display the same halftone, as shown in FIG. 15, the voltage Vsa of the signal line Sa and the voltage Vsb of the signal line Sb vibrate with a constant period and a constant amplitude, respectively. The period of oscillation of the voltages Vsa and Vsb is two horizontal scanning periods (2H). The voltage Vsb of the signal line Sb changes so that the phase differs from the voltage Vsa of the signal line Sa by 180 degrees. In FIG. 15, a period in which the voltages Vsa and Vsb are higher than the voltage of the counter electrode is shown as “+”, and a period in which the voltages Vsa and Vsb are low is shown as “−”. As described above with reference to FIG. 9, in the liquid crystal display device using TFTs, the voltage of the signal line is transmitted to the sub-pixel electrode through the TFT, and then affected by the change in the voltage Vg of the scanning line. A changing pull-in phenomenon occurs. The voltage of the counter electrode is set in consideration of the pulling phenomenon. Although not shown in FIG. 15, the voltages of the signal lines Sc and Se change in the same manner as the voltage Vsa of the signal line Sa, and the voltages of the signal lines Sd and Sf change in the same manner as the voltage Vsb of the signal line Sb. . As described above, a period from the time when the voltage Vg of a certain scanning line is switched from the low level (VgL) to the high level (VgH) until the time when the voltage Vg of the next scanning line is switched from VgL to VgH. Is one horizontal scanning period (1H).

  As shown in FIG. 15, the voltages Vcs1 to Vcs10 of the auxiliary capacity trunk lines CS1 to CS10 have the same amplitude and cycle. Here, the period of the amplitude is 20H. The voltages Vcs1 and Vcs2 have a relationship in which when one voltage changes to VcH, the other voltage changes to VcL, and when one voltage changes to VcL, the other voltage changes to VcH. The voltages Vcs3 and Vcs4, the voltages Vcs5 and Vcs6, the voltages Vcs7 and Vcs8, and the voltages Vcs9 and Vcs10 have the same relationship as the voltages Vcs1 and Vcs2. In addition, the voltages Vcs3 and Vcs4 change by 2H after the changes in the voltages Vcs1 and Vcs2, and thereafter change by 2H from the voltages Vcs5 and Vcs6, the voltages Vcs7 and Vcs8, and the voltages Vcs9 and Vcs10.

  When the scanning line voltage Vg changes from VgL to VgH, the TFT connected to the scanning line is turned on, and the corresponding scanning line voltage Vs is supplied to the sub-pixel connected to the TFT. Next, after the scanning line voltage changes to VgL, the auxiliary capacity trunk line voltage changes, and the amount of change in the auxiliary capacity trunk line voltage (including the change direction and the sign of the change amount) Since they are different from each other, the effective voltages applied to the liquid crystal layers of the sub-pixels are different.

  Here, as an example, changes in voltages of the sub-pixel 1-a-A and the sub-pixel 1-a-B will be described. When the voltage Vg1 of the scanning line G1 changes from VgL to VgH, the liquid crystal capacitors CLC1-aA and CLC1-aB of the sub-pixels 1-aA and 1-aB are charged. When the voltage Vg1 of the scanning line G1 is VgH, the voltage Vsa of the signal line Sa is +, and the liquid crystal capacitors CLC1-a-A, CLC1-a-B of the sub-pixels 1-a-A, 1-a-B are obtained. Is charged to a higher potential than the counter electrode. Thereafter, when the voltage Vg1 of the scanning line G1 changes from VgH to VgL, the liquid crystal capacitors CLC1-aA and CLC1-aB of the sub-pixels 1-aA and 1-aB are electrically connected to the signal line Sa. And the charging of the liquid crystal capacitors CLC1-a-A and CLC1-a-B is completed. After the voltage Vg1 of the scanning line G1 changes from VgH to VgL, the first change of the voltage Vcs1 of the auxiliary capacity trunk line CS1 is an increase, the first change of the voltage Vcs2 of the auxiliary capacity main line CS2 is a decrease, and then the voltage Vcs1 and Vcs2 repeat increasing and decreasing every 10H. Therefore, the absolute value of the effective voltage applied to the liquid crystal layer of the sub-pixel 1-a-A electrically connected to the storage capacitor main line CS1 among the pixels 1-a specified by the scanning line G1 and the signal line Sa. Is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the sub-pixel 1-a-B electrically connected to the storage capacitor main line CS2.

  As described above, the effective voltage applied to the liquid crystal layer of each sub-pixel is that when the voltage change of the corresponding scanning line is changed from VgH to VgL, and the initial voltage change of the corresponding auxiliary capacitance trunk line is increased. When the voltage of the corresponding scanning line is higher than the voltage of the corresponding signal line when the voltage is VgH and the initial voltage change of the corresponding auxiliary capacity trunk line is lower, the voltage of the corresponding scanning line is VgH. Lower than the voltage of the corresponding signal line at the time. As a result, when the symbol attached to the voltage of the signal line when the corresponding scanning line is selected is +, the effective voltage applied to the liquid crystal layer when the voltage change of the auxiliary capacity trunk line is in the increasing direction. The absolute value of the voltage is larger than when the voltage change is in the decreasing direction. When the symbol attached to the voltage of the signal line when the corresponding scanning line is selected is −, the effective voltage applied to the liquid crystal layer when the voltage change of the auxiliary capacity trunk line is in the increasing direction. Is smaller than that when the voltage change is in the decreasing direction.

  As described above, FIG. 14 shows the contrast and polarity of the sub-pixels that have changed within the effective scanning period of a certain frame. In FIG. 14, the symbol “bright” indicates that the sub-pixel is brighter than the other sub-pixel, that is, the absolute value of the effective voltage applied to the liquid crystal layer of the sub-pixel is larger than the other. “Dark” indicates that the sub-pixel is darker than the other sub-pixel, that is, the absolute value of the effective voltage applied to the liquid crystal layer of the sub-pixel is smaller than the other. In FIG. 14, the symbol “+” indicates that the voltage of the subpixel electrode is higher than the voltage of the counter electrode, and the symbol “−” indicates that the voltage of the subpixel electrode is lower than the voltage of the counter electrode. Show. Note that two sub-pixels included in one pixel are adjacent to a pixel having a lower row number and a pixel having a higher row number, but of the two sub-pixels included in one pixel, A subpixel adjacent to a pixel with a smaller number is indicated as “A”, and a subpixel adjacent to a pixel with a higher row number is indicated as “B”.

  Next, with reference to FIGS. 14 and 15, the brightness and polarity of each sub-pixel will be described.

  First, the contrast and polarity of the sub-pixel 1-a-A and the sub-pixel 1-a-B included in the pixel 1-a will be described. As can be understood from FIG. 15, during the period when the voltage Vg1 of the scanning line G1 is VgH, the voltage Vsa of the signal line Sa is higher than the voltage of the counter electrode. Therefore, the polarities of the sub-pixel 1-a-A and the sub-pixel 1-a-B are +. Further, when the voltage Vg1 of the scanning line G1 changes from VgH to VgL, the voltages Vcs1 and Vcs2 of the auxiliary capacity trunk lines CS1 and CS2 corresponding to the respective sub-pixels are shown by arrows in FIG. 15 (first arrow from the left). It is in the state of the position shown by. Therefore, as understood from FIG. 15, after the voltage Vg1 of the scanning line G1 changes from VgH to VgL, the first change of the voltage Vcs1 of the sub-pixel 1-a-A is an increase (this is referred to as “U”). Since the initial change in the voltage Vcs2 of the auxiliary capacity trunk line CS2 of the sub-pixel 1-a-B is a decrease (this is indicated as “D”), the sub-pixel 1-a- The effective voltage of A increases, the effective voltage of the sub-pixel 1-a-B decreases, and the sub-pixel 1-a-A becomes brighter than the sub-pixel 1-a-B.

  Next, the contrast and polarity of the sub-pixels 2-a-A and 2-a-B included in the pixel 2-a will be described. As shown in FIG. 15, during the period when the voltage Vg2 of the scanning line G2 is VgH, the voltage Vsa of the signal line Sa is lower than the voltage of the counter electrode. Therefore, the subpixels 2-a-A and 2-a-B have a negative polarity. Further, after the voltage Vg2 of the scanning line G2 changes from VgH to VgL, the voltages Vcs2 and Vcs3 of the auxiliary capacity trunk lines CS2 and CS3 corresponding to the respective subpixels 2-a-A and 2-a-B are shown in FIG. In the position indicated by the arrow (second arrow from the left). Therefore, as understood from FIG. 15, after the voltage Vg1 of the scanning line G1 changes from VgH to VgL, the first voltage change of the voltage Vcs2 of the auxiliary capacity trunk line CS2 of the subpixel 2-a-A decreases ( “D”), and the first voltage change of the voltage Vcs3 of the auxiliary capacity trunk line CS3 of the sub-pixel 2-a-B is an increase (“U”). Therefore, the absolute value of the effective voltage of the sub-pixel 2-a-A is increased, the absolute value of the effective voltage of the sub-pixel 2-a-B is decreased, and the sub-pixel 2-a-A is sub-pixel 2-a- Brighter than B.

  Next, the contrast and polarity of the sub-pixel 1-b-A and the sub-pixel 1-b-B included in the pixel 1-b will be described. When the voltage Vg1 of the scanning line G1 is VgH, the voltage Vsb of the signal line Sb is lower than the voltage of the counter electrode. Therefore, the subpixel 1-b-A and the subpixel 1-b-B have a negative polarity. When the voltage Vg1 of the scanning line G1 changes from VgH to VgL, the voltages Vcs1 and Vcs2 of the storage capacitor main lines CS1 and CS2 corresponding to the subpixels 1-b-A and 1-b-B are FIG. 15 is in the state indicated by the arrow (the first arrow from the left). Therefore, as understood from FIG. 15, after the voltage Vg1 of the scanning line G1 changes from VgH to VgL, the initial voltage change of the auxiliary capacity trunk voltage of the sub-pixel 1-b-A increases (“U )), And the first voltage change of the voltage Vcs2 of the auxiliary capacitance main line CS2 of the sub-pixel 1-b-B is a decrease (“D”). Therefore, the absolute value of the effective voltage applied to the liquid crystal layer of the sub-pixel 1-b-A decreases, the absolute value of the effective voltage of the sub-pixel 1-b-B increases, and the sub-pixel 1-b-B Brighter than the sub-pixel 1-b-A.

  Next, the contrast and polarity of the sub-pixels 2-b-A and 2-b-B included in the pixel 2-b will be described. As shown in FIG. 15, during the period when the voltage Vg2 of the scanning line G2 is VgH, the voltage Vsb of the signal line Sb is higher than the voltage of the counter electrode. Accordingly, the polarities of the sub-pixels 2-b-A and 2-b-B are +. Further, after the voltage Vg2 of the scanning line G2 changes from VgH to VgL, the voltages Vcs2 and Vcs3 of the auxiliary capacity trunk lines CS2 and CS3 corresponding to the respective subpixels 2-b-A and 2-b-B are shown in FIG. In the position indicated by the arrow (second arrow from the left). Therefore, as understood from FIG. 15, after the voltage Vg1 of the scanning line G1 changes from VgH to VgL, the initial voltage change of the voltage Vcs2 of the auxiliary capacity trunk line CS2 of the subpixel 2-b-A decreases ( “D”), and the first voltage change of the voltage Vcs3 of the auxiliary capacity trunk line CS3 of the sub-pixel 2-b-B is an increase (“U”). Therefore, the effective voltage of the sub-pixel 2-b-A decreases, the effective voltage of the sub-pixel 2-b-B increases, and the sub-pixel 2-b-B becomes brighter than the sub-pixel 2-b-A. From the above, the brightness and polarity of each sub-pixel are as shown in FIG.

  Hereinafter, it will be described that the liquid crystal display device of the present embodiment satisfies the above three conditions. First, it will be described that the liquid crystal display device of the present embodiment satisfies the first condition.

  First, it will be described that the first condition is satisfied, that is, that the absolute value of the effective voltage applied to the liquid crystal layer of each subpixel matches in each direction of the electric field. Here, in the liquid crystal display device of the present embodiment, each pixel has subpixels having different effective voltages to the liquid crystal layer. However, it is a bright subpixel that has a dominant influence on display quality such as display flicker. Since the pixel, that is, the sub-pixel indicated as “bright” in FIG. 14, the first condition is particularly imposed on the sub-pixel indicated by the symbol “bright”.

  The first condition will be described with reference to each voltage waveform shown in FIG. FIG. 15 shows voltages VLsp1-a-A and VLsp2-a-A applied to the liquid crystal layers of “bright” sub-pixels 1-aA and 2-aA having different electric field directions (polarities). ing. In VLsp1-a-A and VLsp2-a-A shown in FIG. 15, the solid line is the voltage of the subpixel electrode of subpixels 1-aA and 2-aA, and the broken line is the voltage of the counter electrode. Since the effective voltage applied to the layer is a voltage difference between the solid line and the broken line, the effective voltage applied to the liquid crystal layer (or the liquid crystal capacitance is charged in each electric field direction) by appropriately setting the voltage of the counter electrode. The first condition can be satisfied by matching the amount of charge) as much as possible.

  Next, it will be described that the second condition is satisfied, that is, that pixels having different polarities are arranged adjacent to each other in each frame period. However, in the liquid crystal display device of the present embodiment, each pixel has a sub-pixel having a different effective voltage to the liquid crystal layer. Therefore, in addition to the second condition being imposed on the pixel, a sub-pixel having the same effective voltage is applied. The second condition is also imposed on the pixels. In particular, as in the case of the second condition, it is important to satisfy the second condition for a bright subpixel, that is, a subpixel indicated by the symbol “bright” in FIG.

  As shown in FIG. 14, the symbols “+” and “−” indicating the polarity (direction of electric field) of each sub-pixel are, for example, (+, −), (+, −) in the row direction (horizontal direction). , (+, −) And a period of 2 pixels (2 columns), and also in the column direction (vertical direction), for example, (+, −), (+, −), (+, −), It is inverted at a cycle of (+, −) and 2 pixels (2 rows). That is, when viewed in units of pixels, a state called dot inversion is exhibited and the second condition is satisfied.

  Next, the bright sub-pixel, that is, the sub-pixel indicated by the symbol “bright” in FIG. 14 is checked. As shown in FIG. 14, when the sub-pixels in the same row, for example, the sub-pixels 1-a-A, 1-b-A, 1-c-A,. The sub-pixels have all the polarities “+”, but the sub-pixels in the same column, for example, the sub-pixels 1-a-A, 1-a-B, 2-a-A, 2-a-B in the first column , 3-a-A, 3-a-B,..., The polarities of the subpixels indicated by the symbol “bright” are “+”, “−”, “+”, “−” and two pixels. (2 rows) Inverted with period. That is, in particular, a subpixel unit having a high luminance ranking shows a state called line inversion, which satisfies the second condition. Further, the sub-pixels indicated by the symbol “dark” are also arranged with the same regularity and satisfy the second condition.

  Next, it will be described that the third condition is satisfied. The third condition is that subpixels having the same luminance order among subpixels having different luminances are arranged so as not to be adjacent to each other as much as possible. In FIG. 14, when a total of four subpixels (for example, subpixels 1-aA, 1-aB, 1-bA, 1-bB) in two rows and two columns are viewed. , “Bright” and “dark” are arranged in the column direction, and “dark” and “bright” are arranged in the column direction of the next row, and when these four subpixels are called one subpixel group, The sub-pixels are arranged so that the sub-pixel group is spread over the entire surface. That is, as shown in FIG. 14, the symbols “bright” and “dark” are arranged in a checkered pattern in units of subpixels, and it can be seen that the third condition is satisfied.

  As described above, the liquid crystal display device according to the present embodiment described with reference to FIGS. 14 and 15 satisfies all the three conditions described above, and thus can realize a high-quality display in which flicker is prevented.

  14 and 15, the sub-pixel brightness and polarity and the voltage waveform changed within the effective scanning period of a certain frame are shown. In the next frame, the voltage of each scanning line is The voltage of the signal line changes in the same manner as the waveform shown in FIG. 15, but the voltage of the storage capacitor main line changes so as to be inverted from the waveform shown in FIG. For this reason, in this frame, as compared with each subpixel shown in FIG. 14, the polarity of each subpixel does not change and the brightness of each subpixel is inverted.

  Further, in the next frame, the voltage of the signal line changes so as to be inverted from the waveform shown in FIG. 15 with respect to the voltage of the scanning line, and the voltage of the storage capacitor main line changes to FIG. The waveform changes so as to be inverted. For this reason, in this frame, as compared with each subpixel shown in FIG. 14, the brightness of each subpixel does not change and the polarity of each subpixel is inverted.

  In the next frame, the voltage of the signal line changes so as to be inverted from the waveform shown in FIG. 15 with respect to the voltage of the scanning line. It changes in the same way as the waveform shown. For this reason, in this frame, the contrast and polarity of each subpixel are inverted as compared with each subpixel shown in FIG.

  Next, with reference to FIG. 16, a change in voltage for a plurality of pixels in the liquid crystal display device of the present embodiment will be described. In FIG. 16, Vcs1 to Vcs6 indicate voltages of the auxiliary capacity trunk lines CS1 to CS6, Vg1 to Vg3 indicate voltages of the scanning lines G1 to G3, and VLsp1-a-A to VLsp3-a-B indicate subpixels 1-a. The effective voltage applied to the liquid crystal layers -A to 3-a-B is shown. In the following description, four consecutive frames are assumed to be frames n, n + 1, n + 2, and n + 3.

  FIG. 16 also shows the vertical scanning period of the input video signal. The vertical scanning period of the input video signal includes an effective scanning period (V-Disp) in which each pixel in the liquid crystal panel 100A (see FIG. 1) is selected for each row, and a vertical in which no pixel in the liquid crystal panel 100A is selected. It consists of a blanking period (V-Blank), and the effective scanning period is determined by the display area (the number of rows of effective pixels) of the liquid crystal panel 100A.

  In this specification, when simply referred to as “vertical scanning period”, “vertical scanning period” means “vertical scanning period of liquid crystal panel”, and “vertical scanning period” (that is, “vertical scanning period of liquid crystal panel”). Is used in a different meaning from the “vertical scanning period of the input video signal”. The “vertical scanning period of the input video signal” is a period of one frame or one field, and means a period starting and ending at a time common to each pixel. The “vertical scanning period” is as described above. Means a period from when a scanning line for writing a display signal voltage is selected until the scanning line is selected for writing the next display signal voltage, and at different times according to the corresponding scanning line Start and end at different times.

  In FIG. 16, the diagonal lines indicate that the start time and end time of the “vertical scanning period” differ depending on the pixel row. As can be understood from FIG. 16, in one frame, the scanning lines are sequentially selected from the first row, and when the scanning line is selected, the voltage of the corresponding subpixel electrode changes. A vertical scanning period in the sub-pixel is started. As described above, the vertical scanning period of the input video signal is composed of the effective scanning period (V-Disp) and the vertical blanking period (V-Blank). It starts from the middle of the effective scanning period, continues through the vertical blanking period, and continues to the middle of the effective scanning period of frame n + 1. Next, when the corresponding scanning line is selected, the next vertical scanning period in the subpixel starts. Note that the length of the “vertical scanning period” is the same as the length of the “vertical scanning period of the input video signal” for any pixel.

  As can be understood from FIG. 16, in the frame n to n + 3, the (brightness, polarity) of the subpixel 1-a-A is (bright, +), (dark, +), (bright,-), (dark, (-) And (light / dark, polarity) of the sub-pixel 1-a-B change in the order of (dark, +), (bright, +), (dark,-), (bright,-). . Further, the (brightness, polarity) of the subpixel 2-a-A changes in order of (bright,-), (dark,-), (bright, +), (dark, +), and the subpixel 2 The (brightness, polarity) of -a-B changes in the order of (dark,-), (bright,-), (dark, +), (bright, +).

  FIG. 17 shows changes in brightness and polarity of the sub-pixels 1-a-A and 1-a-B and the voltage of the first auxiliary capacitance line in the vertical scanning period of the sub-pixels 1-a-A and 1-a-B. Show. As shown in FIG. 17, in the frame n, the polarities of the sub-pixels 1-a-A and 1-a-B are +, and the first auxiliary capacitance line in the vertical scanning period of the sub-pixel 1-a-A The change in voltage is an increase (“↑”), and the change in voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel 1-a-B is a decrease (“↓”). In the frame n + 1, the polarities of the sub-pixels 1-a-A and 1-a-B are +, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the sub-pixel 1-a-A is reduced. (“↓”), the change in voltage of the first auxiliary capacitance line in the vertical scanning period of the sub-pixel 1-a-B is increased (“↑”).

  In the frame n + 2, the polarities of the sub-pixels 1-a-A and 1-a-B are −, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the sub-pixel 1-a-A is reduced (“ ↓ "), the change in voltage of the first auxiliary capacitance line in the vertical scanning period of the sub-pixel 1-a-B is increased (" ↑ "). In the frame n + 3, the subpixels 1-a-A and 1-a-B have a negative polarity, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel 1-aA increases. (“↑”), the change in voltage of the first auxiliary capacitance line in the vertical scanning period of the sub-pixel 1-a-B is reduced (“↓”).

  As described above, (polarity, voltage change at the beginning of the auxiliary capacitance line) of the sub-pixel 1-a-A extends from frame n to n + 3 (+, ↑), (+, ↓), (−, ↓), It changes in the order of (-, ↑), and different combinations appear in order. On the other hand, (polarity, voltage change at the beginning of the auxiliary capacitance wiring) of the sub-pixel 1-a-B is (+, ↓), (+, ↑), (−, ↑), (−, ↓), the combinations having the same polarity as that of the sub-pixel 1-a-A and different voltage changes of the auxiliary capacitance wiring appear in order.

  In the above description, the voltage of the auxiliary capacitance line is periodically changed with 20H as one period in the display period, but the present invention is not limited to this. As shown in FIG. 18A, the voltage of the auxiliary capacitance line may change with 16H as one cycle in the display period. In this case, for example, the voltage of the auxiliary capacitance line changes every 13H in the first and third adjustment periods BH, and the voltage of the auxiliary capacitance line changes every 9H in the second and fourth adjustment periods BH. Alternatively, as shown in FIG. 18B, the voltage of the auxiliary capacitance line may change with 24H as one cycle in the display period. In this case, for example, the voltage of the auxiliary capacitance line changes every 15H in the first and third adjustment periods BH, and the voltage of the auxiliary capacitance line changes every 21H in the second and fourth adjustment periods BH. The voltage change time of the auxiliary capacitance line in the period BH can be appropriately changed according to the value of V-total.

  In the above description, the voltage of the auxiliary capacitance line has changed by one period in the adjustment period, but the present invention is not limited to this. The voltage of the auxiliary capacitance line may change periodically with 2H as one period in each adjustment period as shown in FIG. 19A, or the period with 1H as one period as shown in FIG. 19B. May vary. Alternatively, the voltage of the auxiliary capacitance line may be maintained at the average of VcH and VcL during the adjustment period, as shown in FIG.

  In the above description, one adjustment period exists for one vertical scanning period corresponding to one frame, but the present invention is not limited to this. As shown in FIG. 20, there may be one adjustment period for two vertical scanning periods corresponding to two frames. In FIG. 20, each vertical scanning period is 810H, and the auxiliary capacitance voltages Vcs1 to Vcs3 change periodically with 20H as one period in the display period, and change every 5H in the adjustment period. As described above, when two vertical scanning periods (810H × 2 = 1620H) are an integral multiple of one period (20H) in the display period, a half-period period is provided as an adjustment period in the voltage of the auxiliary capacitance line, and polarity is set. By inversion every two vertical scanning periods, as described with reference to FIG. 17, the first change in the auxiliary capacitance voltage in the third vertical scanning period is changed from the first change in the auxiliary capacitance voltage in the first vertical scanning period. As shown in FIG. 6A, the brightness and polarity of the sub-pixel can be changed.

  In the above description, each adjustment period is an even multiple of the horizontal scanning period, but the present invention is not limited to this. Each adjustment period may be an odd multiple of the horizontal scanning period. As shown in FIG. 21, even when the first and third adjustment periods are 37H and the second and fourth adjustment periods are 27H, the brightness and polarity of the sub-pixels can be adjusted in the same manner as in the case of an even multiple of the horizontal scanning period. By inverting, it is possible to suppress display roughness.

  In the above description, the same storage capacitor line is connected to two subpixels of adjacent pixels, but the present invention is not limited to this. Different auxiliary capacitance lines may be provided for two sub-pixels of adjacent pixels, and the voltage of the auxiliary capacitance lines may be individually changed.

  FIG. 22 shows the contrast and polarity of the sub-pixels changed within the effective scanning period of a certain frame. FIG. 22 shows pixels in the first to sixth rows and the a to f columns. Also here, the liquid crystal display device 100 is provided with ten auxiliary capacity trunk lines CS1 to CS10. As shown in FIG. 22, the auxiliary capacity main line CS1 includes sub-pixels 1-a-A, 1-b-A, 1-c-A,..., Sub-pixels 6-a-A, 6-b-A, 6-c-A,. The trunk line CS2 includes sub-pixels 1-a-B, 1-b-B, 1-c-B... In the first pixel row, sub-pixels 6-a-B, 6-b-B in the sixth pixel row. , 6-c-B... The storage capacitor main line CS3 is connected to the sub-pixels 2-a-A, 2-b-A, and 2-c-A in the second pixel row. As described above, in the liquid crystal display device 100 having the configuration shown in FIG. 22, a certain subpixel and a subpixel included in another pixel adjacent to the subpixel are connected to different auxiliary capacitance trunk lines. The two subpixels are electrically independent.

  FIG. 23 shows an equivalent circuit of the liquid crystal display device 100 having the configuration shown in FIG. 22, and FIG. 24 shows waveforms of various voltages (signals) for driving the liquid crystal display device. In FIG. 24, Vsa indicates the voltage of the signal line Sa, Vsb indicates the voltage of the signal line Sb, Vg1 to Vg12 indicate the voltages of the scanning lines G1 to G12, and Vcs1 to Vcs10 are the voltages of the auxiliary capacitance trunk lines CS1 to CS10. VLsp1-aA to VLsp2-b-B denote effective voltages applied to the liquid crystal layers of the sub-pixels 1-aA to 2-bB. Note that FIG. 24 shows a voltage waveform within one vertical scanning period.

  As shown in FIG. 24, the voltages Vcs1 to Vcs10 of the auxiliary capacity trunk lines CS1 to CS10 have the same amplitude and cycle. Here, the period of the amplitude is 10H. In the voltages Vcs1 and Vcs2, when one voltage is changed to VcH, the other voltage is changed to VcL, and when one voltage is changed to VcL, the other voltage is changed to VcH. The voltages Vcs3 and Vcs4, the voltages Vcs5 and Vcs6, the voltages Vcs7 and Vcs8, and the voltages Vcs9 and Vcs10 have the same relationship. As understood from FIG. 24, after the voltage Vg1 of the scanning line G1 becomes VgL, the voltage Vcs1 increases “↑” and the voltage Vcs2 decreases “↓”. Further, as understood from FIG. 24, after the voltage Vg2 of the scanning line G2 becomes VgL, the voltage Vcs3 decreases “↓” and the voltage Vcs4 increases “↑”.

  In the configuration shown in FIG. 22, since the subpixels in different rows are connected to different storage capacitor trunk lines, the voltage applied to the liquid crystal layer of the subpixel is increased or decreased at the same time in each of the plurality of pixels. Can do. Also in this case, the liquid crystal display device having the configuration shown in FIG. 22 is driven with the voltage waveform shown in FIG. 24 to satisfy all the above three conditions. Can be realized.

  Heretofore, with reference to FIGS. 22 to 24, the brightness and polarity and polarity and voltage waveform of the sub-pixel changed within the effective scanning period of a certain frame have been described. However, in the next frame, the voltage of each scanning line is changed. On the other hand, the voltage of the signal line changes in the same manner as the waveform shown in FIG. 24, but the voltage of the storage capacitor main line changes so as to be inverted from the waveform shown in FIG. For this reason, in this frame, as compared with each subpixel shown in FIG. 22, the polarity of each subpixel does not change, and the brightness of each subpixel is inverted.

  Further, in the next frame, the voltage of the signal line is changed so as to be inverted from the waveform shown in FIG. 24 with respect to the voltage of the scanning line, and the voltage of the auxiliary capacity trunk line is shown in FIG. The waveform changes so as to be inverted. For this reason, in this frame, as compared with each subpixel shown in FIG. 22, the brightness of each subpixel does not change, and the polarity of each subpixel is inverted.

  Further, in the next frame, the voltage of the signal line changes so as to be inverted from the waveform shown in FIG. 24 with respect to the voltage of the scanning line. It changes in the same way as the waveform shown. For this reason, in this frame, the contrast and polarity of each sub-pixel are inverted as compared with each sub-pixel shown in FIG. In this way, also in the liquid crystal display layer having the configuration shown in FIG. 22, it is possible to improve the viewing angle dependency of the γ characteristic and to suppress the deterioration in display quality.

  In the above description, as shown in FIG. 8, the common signal line 14 is provided for the sub-pixels 10a and 10b included in the same pixel 10, but the present invention is not limited to this. Different signal lines may be provided for sub-pixels included in the same pixel. In this case, different effective voltages can be applied to the liquid crystal layer of the sub-pixel by changing the voltage of the signal line without changing the voltage of the auxiliary capacitance line for each sub-pixel.

  FIG. 25 shows a pixel 10 in which signal lines 14a and 14b are provided for two sub-pixels 10a and 10b, respectively. As shown in FIG. 25, the pixel 10 has two subpixel electrodes 18a and 18b connected to different signal lines 14a and 14b via corresponding TFTs 16a and 16b, respectively. Since the sub-pixels 10a and 10b constitute one pixel 10, the gates of the TFTs 16a and 16b are connected to a common scanning line (gate bus line) 12 and are turned on / off by the same scanning signal. A signal voltage (grayscale voltage) is supplied to the signal lines (source bus lines) 14a and 14b so as to satisfy the above relationship. The gates of the TFTs 16a and 16b are preferably shared.

  In the above description, the voltage of the counter electrode is shown constant regardless of time, but the present invention is not limited to this. The voltage of the counter electrode may change with time.

  FIG. 10 shows that the effective voltage of the first subpixel and the effective voltage of the second subpixel are different over a wide gradation range, but the present invention is not limited to this. The effective voltage of each sub-pixel has a specific gradation range (for example, a gradation of 36 gradations to 128 gradations in the case of 256 gradation display in which gradations from black to white are divided into 0 gradations to 255 gradations). The adjustment range) may be different.

  In the above description, it has been shown that the display quality of a normally black mode liquid crystal display device, in particular, an MVA mode liquid crystal display device can be improved. However, the present invention is not limited to this, and an IPS mode liquid crystal display device. It can also be applied to. The problem of the viewing angle dependency of the γ characteristic is more conspicuous in the MVA mode and ASM mode than in the IPS mode. On the other hand, in the IPS mode, it is difficult to manufacture a panel having a high contrast ratio at the time of front observation with high productivity as compared with the MVA mode and the ASM mode. From these points, it is desired to improve the viewing angle dependency of the γ characteristic particularly in the liquid crystal display device of MVA mode or ASM mode.

(Embodiment 2)
Hereinafter, a second embodiment of the liquid crystal display device 100 according to the present invention will be described. The liquid crystal display device 100 of the present embodiment is different from the liquid crystal display device of the first embodiment in the order of changes in brightness, polarity, and effective voltage of subpixels in four consecutive vertical scanning periods. In the following description, in order to avoid redundancy, the description overlapping with that of the first embodiment is omitted.

  With reference to FIG. 26, changes in the brightness of the subpixels and changes in the direction of the electric field, and changes in the effective voltage applied to the liquid crystal layers of the first and second subpixels in the liquid crystal display device 100 of the present embodiment will be described. .

  As shown in FIG. 26A, the periods 1, 4, and 5 are first polarity periods, and the periods 2, 3, and 6 are second polarity periods. Here, looking at four consecutive vertical scanning periods, two are first polarity periods and the remaining two are second polarity periods. For example, in periods 1 to 4 in FIG. 26A, periods 1 and 4 are first polarity periods, and periods 2 and 3 are second polarity periods. In the liquid crystal display device 100 of this embodiment, in the first polarity period, a period satisfying | VLspa |> | VLspb | (here, period 1) and a period satisfying | VLspa | <| VLspb | There is a period 4). In the liquid crystal display device 100, the second polarity period includes a period satisfying | VLspa |> | VLspb | (here, period 3) and a period satisfying | VLspa | <| VLspb | (here, period 2). )

  In FIG. 26B and FIG. 26C, the effective voltages VLspa and VLspb in each vertical scanning period applied to the liquid crystal layers of the first and second subpixels are indicated by bold lines. The effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second subpixels are effective values of the difference between the voltage of the first and second subpixel electrodes and the voltage Vc of the counter electrode. The voltage Vc is shown to be constant.

  In the period 1, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 26A, the period 1 is the first polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 2, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 26A, the period 2 is the second polarity period, and the second subpixel is brighter than the first subpixel.

  In the period 3, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 26A, the period 3 is the second polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 4, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 26A, the period 4 is the first polarity period, and the second subpixel is brighter than the first subpixel. After the period 5, the brightness and polarity of the first and second subpixels are the same as those of the first and second subpixels during the periods 1 to 4.

  From the above, as shown in FIG. 26 (a), the (brightness, polarity) of the first subpixel is (bright, +), (dark,-), (bright,-), (dark, +) in order. In addition, the (brightness, polarity) of the second sub-pixel changes in the order of (dark, +), (bright,-), (dark,-), (bright, +). As described above, in the liquid crystal display device of this embodiment, the brightness of the sub-pixel is inverted every vertical scanning period, and the polarity is inverted every two vertical scanning periods. In the liquid crystal display device according to the present embodiment, as in the liquid crystal display device according to the first embodiment, the brightness of the sub-pixels is inverted every vertical scanning period, so that display roughness can be suppressed. Further, in the liquid crystal display device of the present embodiment, as in the liquid crystal display device of the first embodiment, both the first polarity period and the second polarity period have a period in which the first subpixel is brighter than the second subpixel. Therefore, as shown in FIGS. 26B and 26C, the average of the effective voltage VLspa and the average of the effective voltage VLspb over a plurality of vertical scanning periods (for example, periods 1 to 4) are almost equal. By adjusting the counter voltage, the average of the effective voltages VLspa and VLspb can both be made zero, and as a result, occurrence of reliability problems such as burn-in can be suppressed.

  FIG. 27 shows the changes in brightness and polarity of the first and second subpixels and the voltage of the first auxiliary capacitance line in the vertical scanning period of the first and second subpixels. In FIG. 27, four consecutive frames are indicated as frames n, n + 1, n + 2, and n + 3.

  As shown in FIG. 27, in frame n, the polarities of the first and second subpixels are +, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the first subpixel increases (“↑”). ), The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the second subpixel is reduced (“↓”). In the frame n + 1, the polarity of the first and second subpixels is −, and the change in voltage of the first auxiliary capacitance line in the vertical scanning period of the first subpixel is increased (“↑”). The change in voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is reduced (“↓”).

  In the frame n + 2, the polarity of the first and second subpixels is −, and the change in the voltage of the first auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period is an increase (“↑”). In the frame n + 3, the polarities of the first and second subpixels are +, and the first change in the voltage of the auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is an increase (“↑”).

  In addition, in FIG. 6A referred to for explaining the first embodiment, the brightness and polarity of the sub-pixels in the periods 2 to 5 when it is assumed that the first sub-pixel and the second sub-pixel are interchanged are shown in FIG. This coincides with the contrast and polarity of the sub-pixel in the periods 1 to 4 shown in FIG. Therefore, when the display area of the first subpixel electrode is equal to the display area of the second subpixel electrode, the liquid crystal display device of the present embodiment has substantially the same effect as the liquid crystal display device of the first embodiment.

(Embodiment 3)
Hereinafter, a third embodiment of the liquid crystal display device 100 according to the present invention will be described. The liquid crystal display device 100 of this embodiment is different from the above-described liquid crystal display device in the order of changes in brightness, polarity, and effective voltage of subpixels in four consecutive vertical scanning periods. In the following description, redundant description is omitted to avoid redundancy.

  With reference to FIG. 28, changes in brightness and polarity of subpixels in the liquid crystal display device 100 of the present embodiment, and changes in effective voltage applied to the liquid crystal layers of the first and second subpixels will be described.

  As shown in FIG. 28A, in the liquid crystal display device 100 of the present embodiment, the periods 1, 3 and 5 are first polarity periods, and the periods 2, 4 and 6 are second polarity periods. Here, looking at four consecutive vertical scanning periods, two are first polarity periods and the remaining two are second polarity periods. For example, in periods 1 to 4 in FIG. 28A, periods 1 and 3 are first polarity periods, and periods 2 and 4 are second polarity periods. In the liquid crystal display device 100 of this embodiment, in the first polarity period, a period satisfying | VLspa |> | VLspb | (here, period 1) and a period satisfying | VLspa | <| VLspb | Period 3). In the liquid crystal display device 100, in the second polarity period, a period satisfying | VLspa |> | VLspb | (here, period 2) and a period satisfying | VLspa | <| VLspb | (here, period 4) )

  In FIGS. 28B and 28C, the effective voltages VLspa and VLspb in each vertical scanning period applied to the liquid crystal layers of the first and second subpixels are indicated by thick lines. The effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second subpixels are effective values of the difference between the voltage of the first and second subpixel electrodes and the voltage Vc of the counter electrode. The voltage Vc is shown to be constant.

  In the period 1, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 28A, the period 1 is the first polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 2, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 28A, the period 2 is the second polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 3, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 28A, the period 3 is the first polarity period, and the second subpixel is brighter than the first subpixel.

  In the period 4, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 28A, the period 4 is the second polarity period, and the second subpixel is brighter than the first subpixel. After the period 5, the brightness and polarity of the first and second subpixels are the same as those of the first and second subpixels during the periods 1 to 4. In the liquid crystal display device of this embodiment, the frame frequency is 120 Hz, for example.

  From the above, as shown in FIG. 28A, the (brightness, polarity) of the first sub-pixel is (bright, +), (bright,-), (dark, +), (dark,-) in order. In addition, the (brightness, polarity) of the second sub-pixel changes in the order of (dark, +), (dark,-), (bright, +), (bright,-). As described above, in the liquid crystal display device of this embodiment, the brightness of the sub-pixel is inverted every two vertical scanning periods, and the polarity is inverted every vertical scanning period. In the liquid crystal display device of the present embodiment, unlike the liquid crystal display device of Patent Document 1, the brightness of the sub-pixels is inverted every two vertical scanning periods, so that display roughness can be suppressed. Also, in the liquid crystal display device of this embodiment, unlike the liquid crystal display device of Patent Document 2, the brightness of the first and second subpixels is inverted in both the first polarity period and the second polarity period. As shown in FIG. 28B and FIG. 28C, the average of the effective voltage VLspa and the average of the effective voltage VLspb over a plurality of vertical scanning periods (for example, periods 1 to 4) are substantially equal, As a result of the adjustment, the average of the effective voltages VLspa and VLspb can both be made zero, and as a result, occurrence of reliability problems such as burn-in can be suppressed.

  Next, changes in the effective voltage applied to the liquid crystal layers of the first and second subpixels over a plurality of vertical scanning periods will be described with reference to FIG. In FIG. 29, Vg represents the voltage of the scanning line, Vcsa represents the voltage of the first auxiliary capacitance line, Vcsb represents the voltage of the second auxiliary capacitance line, and VLspa is applied to the liquid crystal layer of the first subpixel. The effective voltage is indicated, and VLspb indicates the effective voltage applied to the liquid crystal layer of the second subpixel. Here, the voltage of the first and second auxiliary capacitance lines increases or decreases every 10H in the display period AH and periodically changes with 20H as one cycle. The voltage of the first and second auxiliary capacitance lines increases or decreases every 18H in the first and third adjustment periods BH, and increases or decreases every 13H in the second and fourth adjustment periods BH.

  As the effective voltage applied to the liquid crystal layers of the first and second subpixels changes according to the change in the voltage of the first and second auxiliary capacitance lines, the (brightness, polarity) of the first subpixel becomes ( It changes in order of bright, +), (bright,-), (dark, +), (dark,-), and (light, dark, polarity) of the second sub-pixel is (dark, +), (dark ,-), (Bright, +), (bright,-). In this way, the brightness and polarity of the first and second sub-pixels change as shown in FIG. 28A, so that the viewing angle dependency of the γ characteristic is improved also in the liquid crystal display device of this embodiment. In the liquid crystal display device thus made, it is possible to suppress deterioration in display quality.

  FIG. 30 shows changes in the brightness and polarity of the first and second subpixels and the voltage of the first auxiliary capacitance line in the vertical scanning period of the first and second subpixels. In FIG. 30, four consecutive frames are indicated as frames n, n + 1, n + 2, and n + 3.

  As shown in FIG. 30, in the frame n, the polarities of the first and second subpixels are +, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the first subpixel increases (“↑”). ), The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the second subpixel is reduced (“↓”). In frame n + 1, the polarities of the first and second subpixels are −, and the first change in the voltage of the auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is an increase (“↑”).

  In frame n + 2, the polarity of the first and second subpixels is +, and the change in the voltage of the first auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period is an increase (“↑”). In the frame n + 3, the polarity of the first and second subpixels is −, and the change in the voltage of the first auxiliary capacitance line during the vertical scanning period of the first subpixel is increased (“↑”). The change in voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is reduced (“↓”).

  As can be understood from a comparison between FIG. 17 and FIG. 30, in the liquid crystal display device of this embodiment, the first change in the voltage of the auxiliary capacitance line in the vertical scanning period of the first and second subpixels is shown in the embodiment. However, the change in polarity is different from that of the liquid crystal display device of the first embodiment.

  Here, the difference in the cycle in which the brightness of the sub-pixel is inverted in the liquid crystal display device of the present embodiment and the liquid crystal display device of the first embodiment will be described. In the liquid crystal display device of the present embodiment, the brightness of the sub-pixel is inverted every two vertical scanning periods as shown in FIG. 28, whereas in the liquid crystal display device of the first embodiment, as shown in FIG. The brightness of the sub-pixel is inverted every vertical scanning period. Therefore, in the liquid crystal display device according to the present embodiment, the period in which the brightness of the sub-pixels is inverted is twice as long as that of the liquid crystal display device according to the first embodiment. As described above, the roughness can be reduced by reversing the brightness of the sub-pixel, but the effect of reducing the roughness is higher as the inversion period of the brightness of the sub-pixel is shorter. On the other hand, if the vertical scanning period becomes too short, the orientation of the liquid crystal molecules cannot be changed sufficiently within one vertical scanning period, and as a result, the predetermined luminance may not be reached. Thus, if the vertical scanning period is too short compared to the response speed of the liquid crystal molecules, a sufficient luminance difference between the sub-pixels cannot be obtained, and the effect of improving the viewing angle dependency of the γ characteristic is reduced.

  Table 1 shows the display quality when the frame frequency is changed for the liquid crystal display devices of Patent Document 1, Patent Document 2, Embodiment 1, and the present embodiment. In Table 1, those with good display quality are indicated with “◯”, and those with poor display quality are indicated with “x”.

  According to Table 1, the liquid crystal display device of Patent Document 1 has a good viewing angle improvement effect for all frame frequencies, but has a problem that display is rough for all frame frequencies. Yes. Further, the liquid crystal display device of Patent Document 2 cannot be used for industrial products because of reliability problems.

  Any of the liquid crystal display devices of Embodiments 1 and 3 does not have the problem of reliability that has been a problem in Patent Document 2, and there is no problem in using it as an industrial product. Furthermore, the liquid crystal display devices of Embodiments 1 and 3 also solve the problem of display roughness that is a problem in Patent Document 1.

  However, when the liquid crystal display devices of the first embodiment and the third embodiment are compared, an optimal selection can be made with respect to the frame frequency in terms of the effect of improving the viewing angle characteristics and the flickering of the display. As shown in Table 1, in the liquid crystal display device of the first embodiment, a good display quality was obtained when the frame frequency was 60 Hz or more and 90 Hz or less, whereas in the liquid crystal display device of the present embodiment, a frame was obtained. If the frequency is 120 Hz or higher, a display without flickering could be realized. In the liquid crystal display device of the present embodiment, it has been experimentally confirmed that if the frame frequency is 120 Hz, the effect of improving the viewing angle dependency of the γ characteristic can be obtained. The response speed is preferably improved by the liquid crystal material and the driving method.

(Embodiment 4)
Hereinafter, a fourth embodiment of the liquid crystal display device 100 according to the present invention will be described. The liquid crystal display device 100 of this embodiment is different from the above-described liquid crystal display device in the order of changes in brightness, polarity, and effective voltage of subpixels in four consecutive vertical scanning periods. In the following description, redundant description is omitted to avoid redundancy.

  With reference to FIG. 31, changes in brightness and polarity of subpixels and changes in effective voltage applied to the liquid crystal layers of the first and second subpixels in the liquid crystal display device 100 of the present embodiment will be described.

  As shown in FIG. 31A, in the liquid crystal display device 100 of the present embodiment, periods 1, 3 and 5 are first polarity periods, and periods 2, 4 and 6 are second polarity periods. Here, looking at four consecutive vertical scanning periods, two are first polarity periods and the remaining two are second polarity periods. For example, in periods 1 to 4 in FIG. 31A, periods 1 and 3 are first polarity periods, and periods 2 and 4 are second polarity periods. In the liquid crystal display device 100 of this embodiment, in the first polarity period, a period satisfying | VLspa |> | VLspb | (here, period 1) and a period satisfying | VLspa | <| VLspb | Period 3). In the liquid crystal display device 100, in the second polarity period, a period satisfying | VLspa |> | VLspb | (here, period 4) and a period satisfying | VLspa | <| VLspb | (here, period 2) )

  In FIG. 31B and FIG. 31C, the effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second sub-pixels in the respective vertical scanning periods are indicated by bold lines. The effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second subpixels are effective values of the difference between the voltage of the first and second subpixel electrodes and the voltage Vc of the counter electrode. The voltage Vc is shown to be constant.

  In the period 1, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 31A, the period 1 is the first polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 2, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 31A, the period 2 is the second polarity period, and the second subpixel is brighter than the first subpixel.

  In the period 3, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 31A, the period 3 is the first polarity period, and the second subpixel is brighter than the first subpixel.

  In the period 4, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 31A, the period 4 is the second polarity period, and the first subpixel is brighter than the second subpixel. After the period 5, the brightness and polarity of the first and second subpixels are the same as those of the first and second subpixels during the periods 1 to 4.

  From the above, as shown in FIG. 31A, (brightness, polarity) of the first subpixel is (bright, +), (dark,-), (dark, +), (bright,-) in order. Further, the (brightness, polarity) of the second sub-pixel changes in the order of (dark, +), (bright,-), (bright, +), (dark,-). As described above, in the liquid crystal display device of this embodiment, the brightness of the sub-pixel is inverted every two vertical scanning periods, and the polarity is inverted every vertical scanning period. In the present embodiment, the frame frequency is 120 Hz, for example.

  FIG. 32 shows the changes in brightness and polarity of the first and second subpixels and the voltage of the auxiliary capacitance wiring at the beginning in the vertical scanning period of the first and second subpixels. In FIG. 32, four consecutive frames are indicated as frames n, n + 1, n + 2, and n + 3.

  As shown in FIG. 32, the polarity of the first and second subpixels is + in the frame n, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the first subpixel increases (“↑”). ), The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the second subpixel is reduced (“↓”). In the frame n + 1, the polarity of the first and second subpixels is −, and the change in voltage of the first auxiliary capacitance line in the vertical scanning period of the first subpixel is increased (“↑”). The change in voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is reduced (“↓”).

  In frame n + 2, the polarity of the first and second subpixels is +, and the change in the voltage of the first auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period is an increase (“↑”). In the frame n + 3, the polarities of the first and second subpixels are −, and the first change in the voltage of the auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is an increase (“↑”).

  In the liquid crystal display device according to the present embodiment, as in the liquid crystal display device according to the third embodiment, the brightness of the sub-pixel is inverted every two vertical scanning periods, so that display roughness can be suppressed. Further, in the liquid crystal display device of the present embodiment, as in the liquid crystal display device of the third embodiment, the brightness of the first and second subpixels is inverted in both the first polarity period and the second polarity period. As shown in FIG. 31 (b) and FIG. 31 (c), the average of the effective voltage VLspa and the average of the effective voltage VLspb over a plurality of vertical scanning periods (for example, periods 1 to 4) are substantially equal, and the counter voltage As a result of the adjustment, the average of the effective voltages VLspa and VLspb can both be made zero, and as a result, occurrence of reliability problems such as burn-in can be suppressed.

  Note that, in FIG. 28A referred to for describing the liquid crystal display device of the third embodiment, the brightness and polarity of the subpixels in the periods 2 to 5 when the polarity is assumed to be reversed are shown in FIG. This corresponds to the contrast and polarity of the subpixels in the periods 1 to 4 shown in FIG. Therefore, the liquid crystal display device of the present embodiment has substantially the same effect as the liquid crystal display device of the third embodiment.

  In the liquid crystal display device according to the third embodiment, when dot inversion driving is performed as described with reference to FIGS. 14 and 15, the contrast and polarity of the sub-pixels 1-a-A and 1-a-B are illustrated. When changing as shown in periods 1 to 4 of 31 (a), the brightness and polarity of subpixels 2-a-A and 2-a-B are as shown in periods 2 to 5 of FIG. 28 (a). Change.

(Embodiment 5)
Hereinafter, a fifth embodiment of the liquid crystal display device according to the present invention will be described. The liquid crystal display device 100 of this embodiment is different from the above-described liquid crystal display device in the order of changes in brightness, polarity, and effective voltage of subpixels in four consecutive vertical scanning periods. In the following description, redundant description is omitted to avoid redundancy.

  With reference to FIG. 33, changes in brightness and polarity of subpixels and changes in effective voltage applied to the liquid crystal layers of the first and second subpixels in the liquid crystal display device 100 of the present embodiment will be described.

  As shown in FIG. 33A, in the liquid crystal display device 100 of the present embodiment, the periods 1, 4 and 5 are first polarity periods, and the periods 2, 3 and 6 are second polarity periods. Here, looking at four consecutive vertical scanning periods, two are first polarity periods and the remaining two are second polarity periods. For example, in periods 1 to 4 in FIG. 33A, period 1 and period 4 are the first polarity period, and period 2 and period 3 are the second polarity period. In the liquid crystal display device 100 of this embodiment, in the first polarity period, a period satisfying | VLspa |> | VLspb | (here, period 1) and a period satisfying | VLspa | <| VLspb | There is a period 4). In the liquid crystal display device 100, in the second polarity period, a period satisfying | VLspa |> | VLspb | (here, period 2) and a period satisfying | VLspa | <| VLspb | (here, period 3) )

  In FIG. 33 (b) and FIG. 33 (c), the effective voltages VLspa and VLspb in each vertical scanning period applied to the liquid crystal layers of the first and second subpixels are indicated by bold lines, respectively. The effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second subpixels are effective values of the difference between the voltage of the first and second subpixel electrodes and the voltage Vc of the counter electrode. The voltage Vc is shown to be constant.

  In the period 1, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 33A, the period 1 is the first polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 2, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 33A, the period 2 is the second polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 3, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 33A, the period 3 is the second polarity period, and the second subpixel is brighter than the first subpixel.

  In the period 4, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 33A, the period 4 is the first polarity period, and the second subpixel is brighter than the first subpixel. After the period 5, the brightness and polarity of the first and second subpixels are the same as those of the first and second subpixels during the periods 1 to 4. In the liquid crystal display device of this embodiment, the frame frequency is 120 Hz, for example.

  From the above, as shown in FIG. 33A, (brightness, polarity) of the first subpixel is (bright, +), (bright,-), (dark,-), (dark, +) in order. In addition, the (brightness, polarity) of the second subpixel changes in the order of (dark, +), (dark,-), (bright,-), (bright, +). As described above, in the liquid crystal display device of the present embodiment, the brightness of the subpixel is inverted every two vertical scanning periods, and the polarity is changed by two vertical scanning when the brightness of the subpixel is inverted and when one vertical scanning period is shifted. It is reversed every period. In the liquid crystal display device of the present embodiment, unlike the liquid crystal display device of Patent Document 1, the brightness of the sub-pixels is inverted every two vertical scanning periods, so that display roughness can be suppressed. Also, in the liquid crystal display device of this embodiment, unlike the liquid crystal display device of Patent Document 2, the brightness of the first and second subpixels is inverted in both the first polarity period and the second polarity period. As shown in FIG. 33 (b) and FIG. 33 (c), the average of the effective voltage VLspa and the average of the effective voltage VLspb over a plurality of vertical scanning periods (for example, periods 1 to 4) are substantially equal, and the counter voltage As a result of the adjustment, the average of the effective voltages VLspa and VLspb can both be made zero, and as a result, occurrence of reliability problems such as burn-in can be suppressed.

  Next, with reference to FIG. 34, a change in voltage over a plurality of vertical scanning periods will be described.

  In FIG. 34, Vg represents the voltage of the scanning line, Vcsa represents the voltage of the first auxiliary capacitance line, Vcsb represents the voltage of the second auxiliary capacitance line, and VLspa is applied to the liquid crystal layer of the first subpixel. The effective voltage is indicated, and VLspb indicates the effective voltage applied to the liquid crystal layer of the second subpixel. Here, the voltage of the first and second auxiliary capacitance lines increases or decreases every 10H in the display period AH and periodically changes with 20H as one cycle. Further, the voltage of the first and second auxiliary capacitance lines increases or decreases every 18H in the first to fourth adjustment periods BH.

  FIG. 35 shows changes in light and darkness and polarity of the first and second subpixels and the voltage of the first auxiliary capacitance line in the vertical scanning period of the first and second subpixels. In FIG. 35, four consecutive frames are indicated as frames n, n + 1, n + 2, and n + 3.

  As shown in FIG. 35, in the frame n, the polarities of the first and second subpixels are +, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the first subpixel increases (“↑”). ), The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the second subpixel is reduced (“↓”). In the frame n + 1, the polarity of the first and second subpixels is −, and the change in the voltage of the first auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is an increase (“↑”).

  In the frame n + 2, the polarity of the first and second subpixels is −, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the first subpixel is increased (“↑”). The change in the voltage of the first auxiliary capacitance line during the vertical scanning period is decreased (“↓”). In the frame n + 3, the polarities of the first and second subpixels are +, and the first change in the voltage of the auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is an increase (“↑”).

  As described above, the effective voltage applied to the liquid crystal layers of the first and second subpixels changes in accordance with the change in the voltage of the first and second auxiliary capacitance lines, so that the (light and dark, (Polarity) changes in order of (bright, +), (bright,-), (dark,-), (dark, +), and (brightness, polarity) of the second subpixel is (dark, It changes in the order of (+), (dark,-), (bright,-) (bright, +). Therefore, also in the liquid crystal display device according to the present embodiment, it is possible to suppress a decrease in display quality in the liquid crystal display device in which the viewing angle dependency of the γ characteristic is improved.

(Embodiment 6)
Hereinafter, a sixth embodiment of the liquid crystal display device according to the present invention will be described. The liquid crystal display device 100 of this embodiment is different from the above-described liquid crystal display device in the order of changes in brightness, polarity, and effective voltage of subpixels in four consecutive vertical scanning periods. In the following description, redundant description is omitted to avoid redundancy.

  With reference to FIG. 36, changes in brightness and polarity of subpixels and changes in effective voltage applied to the liquid crystal layers of the first and second subpixels in the liquid crystal display device 100 of the present embodiment will be described.

  As shown in FIG. 36A, in the liquid crystal display device 100 of the present embodiment, periods 1, 2, 5, and 6 are first polarity periods, and periods 3 and 4 are second polarity periods. Here, looking at four consecutive vertical scanning periods, two are first polarity periods and the remaining two are second polarity periods. For example, in the periods 1 to 4 in FIG. 36A, the period 1 and the period 2 are the first polarity period, and the period 3 and the period 4 are the second polarity period. In the liquid crystal display device 100 of this embodiment, in the first polarity period, a period satisfying | VLspa |> | VLspb | (here, period 1) and a period satisfying | VLspa | <| VLspb | Period 2). In the liquid crystal display device 100, in the second polarity period, a period satisfying | VLspa |> | VLspb | (here, period 4) and a period satisfying | VLspa | <| VLspb | (here, period 3) )

  In FIGS. 36B and 36C, the effective voltages VLspa and VLspb in each vertical scanning period applied to the liquid crystal layers of the first and second sub-pixels are indicated by bold lines, respectively. The effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second subpixels are effective values of the difference between the voltage of the first and second subpixel electrodes and the voltage Vc of the counter electrode. The voltage Vc is shown to be constant.

  In the period 1, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 36A, the period 1 is the first polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 2, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 36A, the period 2 is the first polarity period, and the second subpixel is brighter than the first subpixel.

  In the period 3, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is lower than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 36A, the period 3 is the second polarity period, and the second subpixel is brighter than the first subpixel.

  In the period 4, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 36A, the period 4 is the second polarity period, and the first subpixel is brighter than the second subpixel. After the period 5, the brightness and polarity of the first and second subpixels are the same as those of the first and second subpixels during the periods 1 to 4.

  From the above, as shown in FIG. 36A, (brightness, polarity) of the first subpixel is (bright, +), (dark, +), (dark,-), (bright,-) in order. In addition, the (brightness, polarity) of the second subpixel changes in the order of (dark, +), (bright, +), (bright,-), (dark,-). As described above, in the liquid crystal display device of this embodiment, the brightness of the subpixel is inverted every two vertical scanning periods, and the polarity is shifted by two vertical scans while being shifted by one vertical scanning period from the time when the brightness of the subpixel is inverted. It is reversed every period. In the liquid crystal display device according to the present embodiment, as in the liquid crystal display device according to the fifth embodiment, the brightness of the sub-pixel is inverted every two vertical scanning periods, so that display roughness can be suppressed. Further, in the liquid crystal display device of the present embodiment, as in the liquid crystal display device of the fifth embodiment, the brightness of the first and second subpixels is inverted in both the first polarity period and the second polarity period. 36 (b) and FIG. 36 (c), the average of the effective voltage VLspa and the average of the effective voltage VLspb over a plurality of vertical scanning periods (for example, periods 1 to 4) are substantially equal, and the counter voltage As a result of the adjustment, the average of the effective voltages VLspa and VLspb can both be made zero, and as a result, occurrence of reliability problems such as burn-in can be suppressed.

  FIG. 37 shows changes in the brightness and polarity of the first and second subpixels and the voltage of the first auxiliary capacitance line in the vertical scanning period of the first and second subpixels. In FIG. 37, four consecutive frames are indicated as frames n, n + 1, n + 2, and n + 3.

  As shown in FIG. 37, in frame n, the polarities of the first and second subpixels are +, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the first subpixel increases (“↑”). ), The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the second subpixel is reduced (“↓”). In the frame n + 1, the polarities of the first and second subpixels are +, and the first change in the voltage of the auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is an increase (“↑”).

  In the frame n + 2, the polarity of the first and second subpixels is −, and the change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the first subpixel is increased (“↑”). The change in the voltage of the first auxiliary capacitance line during the vertical scanning period is decreased (“↓”). In the frame n + 3, the polarities of the first and second subpixels are −, and the first change in the voltage of the auxiliary capacitance line during the vertical scanning period of the first subpixel is reduced (“↓”). The change in the voltage of the first auxiliary capacitance line in the vertical scanning period of the subpixel is an increase (“↑”).

  Note that the contrast and polarity of subpixels in periods 2 to 5 when it is assumed that the first subpixel and the second subpixel are interchanged in FIG. 36A are the same as those in FIG. This coincides with the contrast and polarity of the sub-pixel in the periods 1 to 4 shown in (a). Therefore, when the display area of the first subpixel electrode is equal to the display area of the second subpixel electrode, the liquid crystal display device of the present embodiment has substantially the same effect as the liquid crystal display device of the fifth embodiment.

  In the liquid crystal display device according to the sixth embodiment, when dot inversion driving is performed as described with reference to FIGS. 14 and 15, the contrast and polarity of the subpixels 1-a-A and 1-a-B are shown. When changing as shown in periods 1 to 4 of 36 (a), the contrast and polarity of the sub-pixels 2-a-A and 2-a-B are as shown in periods 2 to 5 of FIG. 33 (a). Change.

(Embodiment 7)
Hereinafter, a seventh embodiment of the liquid crystal display device according to the present invention will be described. The liquid crystal display device according to the present embodiment is different from the liquid crystal display devices according to the first to sixth embodiments in that the luminance of the sub-pixel changes through the intermediate luminance. In the following description, redundant description is omitted to avoid redundancy.

  With reference to FIG. 38, changes in brightness and polarity of subpixels in the liquid crystal display device 100 of the present embodiment, and changes in effective voltage applied to the liquid crystal layers of the first and second subpixels will be described. As shown in FIG. 38A, in the liquid crystal display device 100 of the present embodiment, the periods 1, 3 and 5 are first polarity periods, and the periods 2, 4 and 6 are second polarity periods. Here, looking at four consecutive vertical scanning periods, two are first polarity periods and the remaining two are second polarity periods. For example, in the periods 1 to 4, the period 1 and the period 3 are the first polarity period, and the period 2 and the period 4 are the second polarity period. The first polarity period is a period that satisfies | VLspa |> | VLspb | (here, period 1) and a period that satisfies | VLspa | <| VLspb | (here, period 3). The second polarity period Is a period (periods 2 and 4) in which VLspa is equal to VLspb.

  In FIG. 38B and FIG. 38C, the effective voltages VLspa and VLspb in each vertical scanning period applied to the liquid crystal layers of the first and second subpixels are indicated by bold lines. The effective voltages VLspa and VLspb applied to the liquid crystal layers of the first and second subpixels are effective values of the difference between the voltage of the first and second subpixel electrodes and the voltage Vc of the counter electrode. The voltage Vc is shown to be constant.

  In the period 1, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. The absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel (| VLspa |> | VLspb |). Therefore, as shown in FIG. 38A, the period 1 is the first polarity period, and the first subpixel is brighter than the second subpixel.

  In the period 2, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The effective voltage applied to the liquid crystal layer of the first subpixel is equal to the effective voltage applied to the liquid crystal layer of the second subpixel (VLspa = VLspb). Therefore, as shown in FIG. 38A, the period 2 is the second polarity period, and the brightness of the first subpixel is equal to the brightness of the second subpixel.

  In the period 3, the voltage of the first subpixel electrode and the second subpixel electrode is higher than the voltage of the counter electrode. Further, the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel (| VLspa | <| VLspb |). Therefore, as shown in FIG. 38A, the period 3 is the first polarity period, and the second subpixel is brighter than the first subpixel.

  In the period 4, the voltage of the first subpixel electrode and the second subpixel electrode is lower than the voltage of the counter electrode. The effective voltage applied to the liquid crystal layer of the first subpixel is equal to the effective voltage applied to the liquid crystal layer of the second subpixel (VLspa = VLspb). Therefore, as shown in FIG. 38A, the period 4 is the second polarity period, and the brightness of the first subpixel is equal to the brightness of the second subpixel. After the period 5, the brightness and polarity of the first and second subpixels are the same as those of the first and second subpixels during the periods 1 to 4.

  From the above, as shown in FIG. 38A, (brightness, polarity) of the first subpixel is (bright, +), (middle,-), (dark, +), (middle,-) in order. In addition, the (brightness, polarity) of the second subpixel changes in the order of (dark, +), (middle,-), (bright, +), (middle,-). Here, “medium” indicates that the brightness (luminance) of the first sub-pixel is equal to the brightness (luminance) of the second sub-pixel. As described above, in the liquid crystal display device according to the present embodiment, the luminance of the sub-pixel is changed in three stages through the intermediate luminance every vertical scanning period, and the polarity is inverted every vertical scanning period.

  In the liquid crystal display device of this embodiment, the brightness of the sub-pixels is inverted, so that display roughness can be suppressed. In the liquid crystal display device of this embodiment, as shown in FIGS. 38B and 38C, the average and effective of the effective voltage VLspa over a plurality of vertical scanning periods (for example, periods 1 to 4) are obtained. The average of the voltages VLspb is almost equal, and the average of the effective voltages VLspa and VLspb can be made zero by adjusting the counter voltage, thereby suppressing the occurrence of reliability problems such as burn-in. Can do.

  Next, changes in the effective voltage applied to the liquid crystal layer of the sub-pixel in the liquid crystal display device of this embodiment will be described with reference to FIGS. 39A, 39B, and 40. FIG. In the following description, four consecutive frames (vertical scanning periods) are assumed to be frames n, n + 1, n + 2, and n + 3.

  FIG. 39A shows the contrast and polarity of each subpixel changed in frame n, and FIG. 39B shows the contrast and polarity of each subpixel changed in frame n + 1. The liquid crystal display device of this embodiment has a pixel arrangement as shown in FIGS. 39A and 39B, which is the same as the pixel arrangement described in the liquid crystal display device of Embodiment 1 with reference to FIG. It is. Therefore, in order to avoid making the description excessively complicated, redundant description is omitted. In the liquid crystal display device of this embodiment, twelve auxiliary capacity trunk lines are provided. In FIGS. 39A and 39B, the auxiliary capacity lines connected to each of the twelve auxiliary capacity trunk lines are CS1, CS2, and CS3, respectively. ... CS12.

  As an example, changes in brightness and polarity of subpixels included in the pixels 1-a, 1-b, 2-a, and 2-b will be described. In frame n, as shown in FIG. 39A, the polarities of the pixels 1-a and 2-b are the first polarity (+), and the polarities of the pixels 1-b and 2-a are the second polarity (-). It is. Further, the sub-pixels 1-a-A, 1-b-B, 2-a-A, and 2-b-B are brighter than the other sub-pixel. Next, in frame n + 1, as shown in FIG. 39B, each sub-pixel changes to intermediate luminance, and the polarity of each sub-pixel is inverted from that in frame n. Next, in frame n + 2, the polarity of each sub-pixel is inverted from that in frame n + 1, which is the same as that shown in FIG. 39A, and the brightness of the sub-pixel is inverted as shown in FIG. 39A. Next, in the frame n + 3, as shown in FIG. 39B, each sub-pixel changes to an intermediate luminance, and the polarity of each sub-pixel is inverted to the same polarity as shown in FIG. 39B.

  Here, in the liquid crystal display device of the present embodiment, it will be described that the above three conditions are satisfied in order to suppress flicker.

  Further, in the liquid crystal display device according to the present embodiment, similarly to the liquid crystal display device according to the first embodiment described with reference to FIG. The effective voltages applied to the liquid crystal layer in the direction are matched as much as possible, and the first condition is satisfied. Further, in the liquid crystal display device of the present embodiment, as shown in FIGS. 39A and 39B, pixels having different polarities are arranged adjacent to each other, and the second condition is satisfied. Further, in the liquid crystal display device of the present embodiment, subpixels brighter than the other subpixel are randomized as much as possible, specifically, as shown in FIG. 39A, the symbols “bright” and “dark” are subordinates. They are arranged in a checkered pattern in pixel units and satisfy the third condition.

  Table 2 shows the display quality when the frame frequency is changed for the liquid crystal display devices of Embodiments 1, 3 and this embodiment. In Table 2, those with good display quality are indicated by “◯”, and those with poor display quality are indicated by “x”. As shown in Table 2, in the liquid crystal display device of this embodiment, when the frame frequency is 90 Hz or more, good display quality can be obtained.

  Referring to FIG. 40, the voltage of the signal line, the voltage of the first and second auxiliary capacitance trunk lines, the voltage of the scanning line, and the voltage change of the first and second auxiliary capacitance trunk lines in the liquid crystal display device of the present embodiment. The change in effective voltage applied to the liquid crystal layer of the sub-pixel that changes accordingly will be described for sub-pixels 1-a-A and 1-a-B surrounded by broken lines in FIGS. 39A and 39B. In FIG. 40, Vsa indicates the voltage of the signal line Sa, Vsb indicates the voltage of the signal line Sb, Vcs1 indicates the voltage of the first auxiliary capacity trunk line CS1, Vcs2 indicates the voltage of the second auxiliary capacity main line CS2, Vg1 indicates the voltage of the scanning line G1, and VLsp1-aA and VLsp1-aB indicate effective voltages applied to the liquid crystal layers of the sub-pixels 1-aA and 1-aB.

  FIG. 40 shows voltage waveforms in four frames n to n + 3. As described with reference to FIGS. 38, 39A, and 39B, the luminance of the sub-pixel 1-a-A is increased (bright). , Medium, dark, medium), and the luminance of the sub-pixel 1-a-B is changed to (dark, medium, bright, medium), and the respective polarities are inverted to (+,-, +,-). . The writing operation for each frame is started from the time when the voltage Vg1 of the scanning line G1 becomes VgH (high level). One vertical scanning period (V-Total) of the input video signal is 801H. The voltage Vcs1 of the first auxiliary capacity trunk line CS1 is a waveform in which the first level (VL1), the second level (VL2), the third level (VL3), and the second level (VL2) are alternately switched every 6H. The voltages Vcs1 and Vcs2 are 180 ° out of phase with each other.

  In FIG. 40, a period from when the voltage Vg1 of the scanning line G1 becomes VgL (low level) to when the levels of the voltages Vcs1 and Vcs2 of the auxiliary capacitance lines first change is 3H. The period of the display period (the period of the first waveform) of the voltage Vcs1 of the first auxiliary capacity trunk line CS1 is 24H, and the period in which the amplitude is a constant value (first level, second level, and third level) is 6H. Therefore, 3H corresponds to a half of a period in which the amplitude of the voltage Vcs of the auxiliary capacitance line is a constant value (= a period of a quarter of the period in the display period).

  When the scanning line G1 is selected in the frames n and n + 2, the voltage Vsa of the signal line Sa is higher than the voltage of the counter electrode. Further, when the scanning line G1 is selected in the frames n + 1 and n + 3, the voltage Vsa of the signal line Sa is lower than the voltage of the counter electrode.

  Hereinafter, with reference to FIG. 40, the contrast and polarity from the frame n to the frame n + 3 in the sub-pixels 1-a-A and 1-a-B of the pixel 1-a will be described.

  In the frame n, the scanning line G1 is selected (the scanning line voltage Vg is VgH) when the voltage Vcs1 of the first auxiliary capacitance main line is decreased from the second level and maintained at the first level. . When the scanning line G1 is selected, a voltage higher than the voltage of the counter electrode is applied to the subpixel electrodes of the subpixels 1-aA and 1-aB. After the voltage Vg1 of the scanning line G1 returns to VgL, the voltage Vcs1 of the first auxiliary capacitance trunk line changes periodically. When the voltage Vg1 of the scanning line G1 returns from VgH to VgL, the voltage Vcs1 of the first auxiliary capacitance trunk line is VL1, and the voltage Vcs2 of the second auxiliary capacitance trunk line is VL3. Since the average voltage VL2 of the voltages Vcs1 and Vcs2 of the first and second auxiliary capacitance main lines is higher than VL1 and lower than VL3, the absolute value of the effective voltage applied to the liquid crystal layer of the subpixel 1-a-A. Is larger than the absolute value of the effective voltage applied to the liquid crystal layer of the sub-pixel 1-a-B. Thereby, the sub-pixel 1-a-A becomes brighter than the sub-pixel 1-a-B.

  Next, in the frame n + 1, the scanning line G1 is selected when the voltage Vcs1 of the first auxiliary capacitance main line is decreased from the third level and maintained at the second level (the scanning line voltage Vg becomes VgH). . When the scanning line G1 is selected, a voltage lower than the voltage of the counter electrode is applied to the subpixel electrodes of the subpixels 1-aA and 1-aB. After the voltage Vg1 of the scanning line G1 returns to VgL, the voltage Vcs1 of the first auxiliary capacitance trunk line changes periodically. When the voltage Vg1 of the scanning line G1 returns to VgL, the voltages Vcs1 and Vcs2 of the first and second auxiliary capacitance trunk lines are VL2 which is the same as the average voltage of the voltages Vcs1 and Vcs2 of the first and second auxiliary capacitance trunk lines. Therefore, the absolute value of the effective voltage applied to the liquid crystal layer of the sub-pixel 1-a-A is equal to the absolute value of the effective voltage applied to the liquid crystal layer of the sub-pixel 1-a-B. The brightness of the pixel 1-a-A is equal to the brightness of the sub-pixel 1-a-B.

  Next, in the frame n + 2, the scanning line G1 is selected when the voltage Vcs1 of the first auxiliary capacitance trunk line rises from the second level to the third level (the scanning line voltage Vg1 becomes VgH). When the scanning line G1 is selected, a voltage higher than the voltage of the counter electrode is applied to the subpixel electrodes of the subpixels 1-aA and 1-aB. When the voltage Vg1 of the scanning line G1 returns from VgH to VgL, the voltage Vcs1 of the first auxiliary capacitance trunk line is VL3, and the voltage Vcs2 of the second auxiliary capacitance trunk line is VL1, so that the sub-pixel 1-a-A The absolute value of the effective voltage applied to the liquid crystal layer is smaller than the absolute value of the effective voltage applied to the liquid crystal layer of the subpixel 1-a-B. Thereby, the sub-pixel 1-a-A becomes darker than the sub-pixel 1-a-B.

  Next, in the frame n + 3, the scanning line G1 is selected after the voltage Vcs1 of the first auxiliary capacitance trunk line has increased from the first level to the second level (the scanning line voltage Vg becomes VgH). When the scanning line G1 is selected, a voltage lower than the voltage of the counter electrode is applied to the subpixel electrodes of the subpixels 1-aA and 1-aB. Since the voltages Vcs1 and Vcs2 of the first and second storage capacitor main lines when the voltage Vg1 of the scanning line G1 returns from VgH to VgL are VL2, the effective voltage applied to the liquid crystal layer of the sub-pixel 1-a-A. Is equal to the absolute value of the effective voltage applied to the liquid crystal layer of the sub-pixel 1-a-B, so that the brightness of the sub-pixel 1-a-A is the same as that of the sub-pixel 1-a-B. Is equal to the brightness.

  As can be understood from the description with reference to FIG. 40, (brightness, polarity) of the subpixel 1-a-A is (bright, +), (middle, −), (dark, +), (middle, −). In addition, the (brightness, polarity) of the sub-pixel 1-a-B changes in the order of (dark, +), (middle,-), (bright, +), (middle,-). . Although not shown here, the (brightness, polarity) of the sub-pixel 2-a-A is in the order of (bright,-), (middle, +), (dark,-), (middle, +). To change. As described above, in the liquid crystal display device according to the present embodiment, the brightness of the sub-pixel is changed for each vertical scanning period between bright, medium, dark, and medium, and the polarity is inverted for each vertical scanning period. Can be suppressed. Further, in the liquid crystal display device of the present embodiment, as in the liquid crystal display device of the first embodiment, both the first polarity period and the second polarity period have a period in which the first subpixel is brighter than the second subpixel. Therefore, as shown in FIGS. 38B and 38C, the average of the effective voltage VLspa and the average of the effective voltage VLspb over a plurality of vertical scanning periods (for example, periods 1 to 4) are almost equal. By adjusting the counter voltage, the average of the effective voltages VLspa and VLspb can both be made zero, and as a result, occurrence of reliability problems such as burn-in can be suppressed.

  In the liquid crystal display devices of Embodiments 1 to 7 described above, the number of subpixels constituting one pixel is two. However, the present invention is not limited to this, and the number of subpixels is set to three or more. Also good. As the number of subpixels increases, the effect of improving the shift amount of the γ characteristic increases. By increasing the number of pixel divisions from 2 to 4, the change in the shift amount with respect to the change in display gradation becomes smooth, and the display quality is further improved. However, as the number of divisions increases, the transmittance (front) during white display decreases. In particular, when the number of divisions is increased from 2 to 4, the transmittance during white display is significantly reduced. The main reason for this remarkable decrease is that the display area of one subpixel is significantly decreased. In consideration of the effect of improving the viewing angle dependency of the γ characteristic and the white display transmittance, the number of divisions may be appropriately adjusted according to the use of the liquid crystal display device. The improvement effect is most noticeable in the difference between the case of no pixel division and the case of pixel division (in the case of two subpixels), and white display accompanying an increase in the number of subpixels. In consideration of a decrease in time transmittance and a decrease in mass productivity, the number of subpixels per pixel is preferably two.

  Note that, as described with reference to FIGS. 13 and 14, a configuration in which the voltage Vcs is independently supplied to each auxiliary capacitance line may be employed. In this case, there is an advantage that the choices of the waveform of the voltage Vcs in the display period and the adjustment period are increased. However, the level of the voltage Vcs needs to change at least once after the voltage of the scanning line is set to the low level within one vertical scanning period. In addition, for example, in a liquid crystal display device having a configuration in which an auxiliary capacitance line twice the scanning line and a voltage Vcs are independently supplied to each auxiliary capacitance line, only once after the voltage of the scanning line is set to the low level. When the level of the voltage Vcs is changed, the time from when the voltage of the scanning line is changed to the low level until the level of the voltage Vcs changes within one vertical scanning period or after the level change of the voltage Vcs is performed. Next, it is desirable that the time until the scanning line voltage is set to the high level is set to be equal for all display lines.

  On the other hand, when a configuration in which a plurality of auxiliary capacitance lines are provided for each of the plurality of auxiliary capacitance trunk lines, the amplitudes of vibrations of the voltages Vcs of the plurality of auxiliary capacitance lines connected to one auxiliary capacitance trunk line are accurately matched. The advantage is that Of course, there is also an advantage that the circuit configuration can be simplified rather than providing a large number of independent voltages.

  Furthermore, in the liquid crystal display devices of the first to seventh embodiments described above, the multi-pixel driving method described in Patent Document 1, that is, two rectangular wave voltages are applied to the CS bus line, thereby forming two pixels constituting one pixel. Although the method of varying the luminance of the sub-pixel has been adopted, the present invention is not limited to this.

  The gist of the present invention is the following two points, and an embodiment that satisfies these two points is not limited to the above embodiment.

  The first essential point of the present invention is that the luminance of each subpixel is averaged over a certain period of time by replacing the luminance of the subpixels constituting one pixel so that the luminance difference between the subpixels becomes substantially zero. The purpose is to optimize the temporal change of the luminance of the pixel.

  The second essential point of the present invention is that the polarity of the sub-pixels is inverted so that the value obtained by averaging the voltages applied to the sub-pixels over a certain period of time is substantially the same for all the sub-pixels, and is applied to the liquid crystal layer. It is to optimize the change in effective voltage (change in luminance). From the viewpoint of reliability, it is desirable that the difference in average effective voltage between subpixels is 1 V or less.

  As an example of a liquid crystal display device that satisfies the above two points, four frames, (bright, +), (bright, −), which combine pixel polarity (+, −) and subpixel brightness (bright, dark) ), (Dark, +), and (dark, −) include the same amount within a certain period. Further, as another liquid crystal display device, in a configuration having intermediate brightness of light and dark, (bright, +), (dark, +) and (middle,-), (middle,-) or (bright,-), (dark, Some frames include the same amount of four frames (-), (middle,-), and (middle,-) within a certain period.

  In order to satisfy the above points, the present invention is not limited to the liquid crystal display devices of Embodiments 1 to 7 described above, and the polarity and luminance of subpixels may be controlled for each frame. For example, a liquid crystal display device in which the TFT element of each subpixel is driven by an independent data signal or scanning signal for each subpixel may be used.

  Alternatively, as shown in FIG. 25, the liquid crystal display device of the present invention is a liquid crystal display device in which the TFT element of each subpixel controls the luminance with an independent data signal for each subpixel and is driven by a common scanning line. It may be. In this case, the luminance and polarity of each sub-pixel can be controlled by supplying the luminance and polarity of the sub-pixel with independent data signals.

  Alternatively, the liquid crystal display device of the present invention may be a liquid crystal display device in which the TFT element of each subpixel controls the luminance with a common data signal for each subpixel and is driven by a separate scanning line. In this case, the time for one frame is further divided, the luminance and polarity corresponding to each subpixel are supplied to the data signal, and the scanning time or timing is set for each subpixel (time division within one frame). The brightness and polarity of each sub-pixel can be controlled.

  For reference, the disclosure of Japanese Patent Application No. 2006-228476, which is the basic application of the present application, and related Japanese Patent Application No. 2006-228475 are incorporated herein by reference.

  According to the present invention, there is provided a large-sized or high-definition liquid crystal display device with extremely high display quality in which the viewing angle dependency of the γ characteristic is improved. The liquid crystal display device of the present invention is suitably used as a large television receiver of, for example, 30 type or more.

Claims (20)

Each is a liquid crystal display device comprising a plurality of pixels including a first subpixel and a second subpixel,
Each of the first subpixel and the second subpixel includes a counter electrode, a subpixel electrode, and a liquid crystal layer disposed between the counter electrode and the subpixel electrode.
The subpixel electrodes of the first subpixel and the second subpixel are respectively separate first subpixel electrodes and second subpixel electrodes, and the first subpixel and the second subpixel, respectively. The counter electrode is a common single electrode,
When displaying a predetermined intermediate gradation over four or more consecutive even vertical scanning periods, the first subpixel and the second subpixel in at least two vertical scanning periods among the even vertical scanning periods. Of the first sub-pixel and the second sub-pixel, the length of the first polarity period in which the polarity of the even number of vertical scanning periods is the first polarity and the second polarity is the second polarity. The length of the period is equal, and an average value of effective voltages applied to the liquid crystal layer of the first subpixel and the liquid crystal layer of the second subpixel in each of the first polarity period and the second polarity period A liquid crystal display device in which a difference from an average value of applied effective voltages is substantially zero. In each of the plurality of pixels, if the effective voltage applied to the liquid crystal layer of the first subpixel is VLspa and the effective voltage applied to the liquid crystal layer of the second subpixel is VLspb, 4 consecutive Of the two vertical scanning periods, two vertical scanning periods are the first polarity period, and the remaining two vertical scanning periods are the second polarity period,
Of the two vertical scanning periods of at least one of the first polarity period and the second polarity period, one satisfies | VLspa |> | VLspb | and the other satisfies | VLspa | <| VLspb |. Item 2. A liquid crystal display device according to item 1. In each of the plurality of pixels, if the effective voltage applied to the liquid crystal layer of the first subpixel is VLspa and the effective voltage applied to the liquid crystal layer of the second subpixel is VLspb, 4 consecutive Of the two vertical scanning periods, two vertical scanning periods are the first polarity period, and the remaining two vertical scanning periods are the second polarity period,
The value of V | Lspa | and the value of | VLspb | in one of the two vertical scanning periods of at least one of the first polarity period and the second polarity period are the other vertical scanning period. The liquid crystal display device according to claim 1, wherein a value of | VLspb | and a value of | VLspa |   4. The liquid crystal display according to claim 2, wherein the number of vertical scanning periods satisfying | VLspa |> | VLspb | among the four vertical scanning periods is equal to the number of vertical scanning periods satisfying | VLspa | <| VLspb |. apparatus. The plurality of pixels are arranged in a matrix in a plurality of row directions and a plurality of column directions,
5. The liquid crystal display device according to claim 1, wherein in each of the plurality of pixels, the first sub-pixel and the second sub-pixel are arranged along the column direction. 6.   The voltage of the first subpixel electrode and the second subpixel electrode in each of the plurality of pixels changes according to a change in voltage of the corresponding auxiliary capacitance line. Liquid crystal display device.   The voltage of the auxiliary capacitance line corresponding to the first subpixel electrode in each of the plurality of pixels changes in a direction different from the voltage of the auxiliary capacitance line corresponding to the second subpixel electrode. The liquid crystal display device described.   The voltage of the second subpixel electrode of a certain pixel of the plurality of pixels and the voltage of the first subpixel electrode of a pixel adjacent to the certain pixel in the column direction are voltages of a common auxiliary capacitance line. The liquid crystal display device according to claim 5, wherein the liquid crystal display device changes according to the change.   The voltage of the second subpixel electrode of a certain pixel of the plurality of pixels and the voltage of the first subpixel electrode of a pixel adjacent in the column direction of the certain pixel are different in voltage change of auxiliary capacitance wiring. The liquid crystal display device according to claim 5, which changes according to   10. The liquid crystal according to claim 1, wherein in each of the plurality of pixels, the first subpixel electrode is connected to the same signal line as the second subpixel electrode via a corresponding switching element. Display device.   In each of the plurality of pixels, the first subpixel electrode is connected to a first signal line via a first switching element, and the second subpixel electrode is connected to a second signal line via a second switching element. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is connected to the liquid crystal display device.   Of the two vertical scanning periods of the first polarity period and the second polarity period, one is a vertical scanning period satisfying | VLspa |> | VLspb |, and the other is | VLspa | <| VLspb | The liquid crystal display device according to claim 1, wherein the liquid crystal display device is in a vertical scanning period to be satisfied.   In each of the plurality of pixels, the magnitude relationship between | VLspa | and | VLspb | is inverted every one vertical scanning period, and the polarities of the first subpixel and the second subpixel are changed every two vertical scanning periods. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is inverted.   The liquid crystal display device according to claim 1, wherein the frame frequency is 60 Hz.   In each of the plurality of pixels, the magnitude relationship between | VLspa | and | VLspb | is inverted every two vertical scanning periods, and the polarities of the first subpixel and the second subpixel are changed every vertical scanning period. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is inverted.   The liquid crystal display device according to claim 15, wherein the frame frequency is 120 Hz. In each of the plurality of pixels, the magnitude relationship between | VLspa | and | VLspb | is inverted every two vertical scanning periods, and the polarities of the first subpixel and the second subpixel are changed every two vertical scanning periods. Invert,
The liquid crystal according to claim 1, wherein the magnitude relationship between | VLspa | and | VLspb | is reversed when the polarity of the first subpixel and the second subpixel is different from that when the polarity is inverted. Display device. Of the two vertical scanning periods of the first polarity period and the second polarity period, one is a vertical scanning period satisfying | VLspa |> | VLspb |, and the other is | VLspa | <| VLspb | A vertical scanning period to satisfy,
12. The liquid crystal display device according to claim 1, wherein VLspa is equal to VLspb in each of the other two vertical scanning periods of the first polarity period and the second polarity period.   The voltage of the auxiliary capacitance line corresponding to the first subpixel electrode and the second subpixel electrode is a first level, a second level higher than the first level, and a higher voltage than the second level. The liquid crystal display device according to claim 18, wherein the liquid crystal display device changes between the third level and the third level.   The liquid crystal display device according to claim 1, wherein the first subpixel electrode has a display area equal to that of the second subpixel electrode.

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