EP2284829A1 - Flüssigkristallanzeigeanordnung - Google Patents

Flüssigkristallanzeigeanordnung Download PDF

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Publication number
EP2284829A1
EP2284829A1 EP10015233A EP10015233A EP2284829A1 EP 2284829 A1 EP2284829 A1 EP 2284829A1 EP 10015233 A EP10015233 A EP 10015233A EP 10015233 A EP10015233 A EP 10015233A EP 2284829 A1 EP2284829 A1 EP 2284829A1
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EP
European Patent Office
Prior art keywords
liquid crystal
subpixel
subpixels
periods
vertical scanning
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10015233A
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English (en)
French (fr)
Inventor
Fumikazu Shimoshikiryoh
Masae Kitayama
Kentaro Irie
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Sharp Corp
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Sharp Corp
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Publication of EP2284829A1 publication Critical patent/EP2284829A1/de
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3614—Control of polarity reversal in general
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix
    • G09G3/3655—Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/04—Structural and physical details of display devices
    • G09G2300/0421—Structural details of the set of electrodes
    • G09G2300/0426—Layout of electrodes and connections
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/04—Structural and physical details of display devices
    • G09G2300/0439—Pixel structures
    • G09G2300/0443—Pixel structures with several sub-pixels for the same colour in a pixel, not specifically used to display gradations
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
    • G09G2300/0809—Several active elements per pixel in active matrix panels
    • G09G2300/0842—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
    • G09G2300/0852—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor being a dynamic memory with more than one capacitor
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0262—The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0673—Adjustment of display parameters for control of gamma adjustment, e.g. selecting another gamma curve
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/04—Display protection
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source

Definitions

  • the present invention relates to a liquid crystal display device and more particularly relates to a liquid crystal display device that can reduce the viewing angle dependence of the ⁇ characteristic thereof.
  • a liquid crystal display is a flat-panel display that has a number of advantageous features including high resolution, drastically reduced thickness and weight, and low power dissipation.
  • the LCD market has been rapidly expanding recently as a result of tremendous improvements in its display performance, significant increases in its productivity, and a noticeable rise in its cost effectiveness over competing technologies.
  • a twisted-nematic (TN) mode liquid crystal display device which used to be used extensively in the past, is subjected to an alignment treatment such that the major axes of its liquid crystal molecules, exhibiting positive dielectric anisotropy, are substantially parallel to the respective principal surfaces of upper and lower substrates and are twisted by about 90 degrees in the thickness direction of the liquid crystal layer between the upper and lower substrates.
  • the liquid crystal molecules change their orientation directions into a direction that is parallel to the electric field applied.
  • the TN mode liquid crystal display device utilizes variation in the optical rotatory characteristic of its liquid crystal layer due to the change of orientation directions of the liquid crystal molecules in response to the voltage applied, thereby controlling the quantity of light transmitted.
  • the TN mode liquid crystal display device allows a broad enough manufacturing margin and achieves high productivity.
  • the display performance e.g., the viewing angle characteristic, in particular
  • the contrast ratio of the image decreases significantly.
  • the grayscale characteristic of the image being displayed thereon may sometimes invert itself. That is to say, a portion of an image, which looks darker when viewed straight, may look brighter when viewed obliquely. This is a so-called "grayscale inversion phenomenon".
  • an inplane switching (IPS) mode liquid crystal display device To improve the viewing angle characteristic of such a TN mode liquid crystal display device, an inplane switching (IPS) mode liquid crystal display device, a multi-domain vertical aligned (MVA) mode liquid crystal display device, an axisymmetric aligned (ASM) mode liquid crystal display device, and other types of liquid crystal display devices were developed recently.
  • IPS inplane switching
  • MVA multi-domain vertical aligned
  • ASM axisymmetric aligned
  • Liquid crystal displays employing any of the novel modes described above solve the concrete problems with viewing angle characteristics, specifically, the problems that the display contrast ratio decreases considerably or the grayscales invert when the display surface of the display is viewed obliquely.
  • the r characteristic of LCDs would vary with the viewing angle. That is to say, the ⁇ characteristic when an image on the screen is viewed straight is different from the characteristic when it is viewed obliquely.
  • the " ⁇ characteristic” refers to the grayscale dependence of display luminance. That is why if the ⁇ characteristic when the image is viewed straight is different from the characteristic when the same image is viewed obliquely, then it means that the grayscale display state changes according to the viewing direction. This is a serious problem particularly when a still picture such as a photo is presented or when a TV program is displayed.
  • such viewing angle dependence of the ⁇ characteristic can be reduced by providing two or more subpixels for each single pixel and by making the luminance of one of the two subpixels different from that of the other when a moderate luminance is displayed (see Patent Documents Nos. 1 and 2, for example).
  • the liquid crystal display device disclosed in Patent Document No. 1 applies a different effective voltage to the liquid crystal layer of a second subpixel from the one applied to the liquid crystal layer of a first subpixel when a moderate luminance is displayed, thereby making the luminances of the first and second subpixels different from each other and reducing the viewing angle dependence of the ⁇ characteristic.
  • the transmittance of the liquid crystal layer changes with the absolute value of the effective voltage irrespective of the direction of the electric field applied to the liquid crystal layer (i.e., the direction of the electric line of force).
  • the liquid crystal display device disclosed in Patent Document No. 1 inverts the direction of the electric field applied to the liquid crystal layer alternately every vertical scanning period, thereby flattening the uneven distribution of DC levels and overcoming residual image and other reliability-related problems.
  • the liquid crystal display device disclosed in Patent Document No. 2 inverts the brightness levels of first and second subpixels every vertical scanning period (e.g., makes the luminance of the first subpixel higher than that of the second subpixel in a first vertical scanning period but makes the luminance of the second subpixel higher than that of the first subpixel in a second vertical scanning period).
  • the device also inverts the direction of the electric field applied to the liquid crystal layer every vertical scanning period, too. If one of multiple subpixels were always bright, then the image on the screen would look non-smooth.
  • the liquid crystal display device disclosed in Patent Document No. 2 minimizes such non-smoothness of the image on the screen by inverting the brightness levels of the first and second subpixels one vertical scanning period after another.
  • multi-pixel display such a display or driving method that reduces the viewing angle dependence of the ⁇ characteristic by making the luminances of multiple subpixels different from each other
  • a multi-pixel display a “multi-pixel drive”
  • an "area grayscale display” or an “area grayscale drive” a display or driving method that reduces the viewing angle dependence of the ⁇ characteristic by making the luminances of multiple subpixels different from each other
  • the direction of the electric field applied to the liquid crystal layer and the brightness levels of the subpixels are inverted every vertical scanning period, the direction of the electric field applied to the liquid crystal layer is always the same when one of the two subpixels is brighter than the other subpixel.
  • the electric field applied to the liquid crystal layer is directed from a subpixel electrode toward a counter electrode.
  • the electric field with such a direction is supposed to have a first polarity.
  • the electric field applied to the liquid crystal layer is directed from the counter electrode toward the subpixel electrode.
  • the electric field with such a direction is supposed to have a second polarity.
  • the electric field has the first polarity.
  • the electric field has the second polarity.
  • the electric field always has the first polarity when the effective voltage applied to the first subpixel has the greater absolute value and always has the second polarity when the effective voltage applied to the second subpixel has the greater absolute value. That is why the average effective voltages applied to the first and second subpixels have the first and second polarities, respectively.
  • a normal liquid crystal display device In a normal liquid crystal display device, if the same image continues to be presented for a long time with the average of the voltages applied to a pixel kept unequal to zero (i.e., with a DC voltage component left in the voltage applied to the pixel), then that image that has been presented for a long time will still remain on the screen even when the images on the screen are changed after that. That is to say, a so-called "residual image" phenomenon will occur. To avoid such a residual image phenomenon, a normal liquid crystal display device performs an AC drive on (i.e., applies voltages with two different polarities but with the same absolute value to) pixels, thereby making the average of the voltages applied to the liquid crystal layer equal to zero. Furthermore, if the average of the voltages applied does not become equal to zero even by the AC drive, then the normal liquid crystal display device further regulates the counter voltage, thereby setting the average voltage equal to zero.
  • the respective effective voltages applied to the first and second subpixels have mutually different averages. That is why even if the counter voltage is regulated, only the average voltage applied to one of the two subpixels can be made equal to zero and the average voltage applied to the other subpixel cannot be zero. In that case, the residual image phenomenon will occur in the subpixel with the non-zero average voltage. As a result, the residual image phenomenon cannot be eliminated from the overall display device. Consequently, in the liquid crystal display device disclosed in Patent Document No. 2, not both of the average voltages applied to the first and second subpixels can be equal to zero, and therefore, the residual image and other reliability-related problems should arise.
  • the present invention has an object of providing a liquid crystal display device that can resolve those reliability-related problems such as non-smoothness of the image on the screen and the residual image phenomenon.
  • a liquid crystal display device includes a plurality of pixels, each including a first subpixel and a second subpixel.
  • Each of the first and second subpixels includes: a counter electrode; a subpixel electrode; and a liquid crystal layer interposed between the counter electrode and the subpixel electrode.
  • the subpixel electrodes of the first and second subpixels are provided separately from each other as first and second subpixel electrodes, respectively, while the first and second subpixels share the same counter electrode with each other.
  • the first and second subpixels When a predetermined grayscale tone is displayed continuously through four or more consecutive even number of vertical scanning periods, the first and second subpixels have mutually different luminances in at least two of the even number of vertical scanning periods, first polarity periods that are included in the even number of vertical scanning periods and that maintain a first polarity are as long as second polarity periods that are also included in the even number of vertical scanning periods and that maintain a second polarity for each of the first and second subpixels, and in each of the first and second polarity periods, the difference between the average of effective voltages applied to the liquid crystal layer of the first subpixel and that of effective voltages applied to the liquid crystal layer of the second subpixel is substantially equal to zero.
  • the effective voltages applied to the respective liquid crystal layers of the first and second subpixels of each said pixel are represented by VLspa and VLspb, respectively, then two of the four consecutive vertical scanning periods are the first polarity periods and the other two vertical scanning periods are the second polarity periods.
  • the effective voltages applied to the respective liquid crystal layers of the first and second subpixels of each said pixel are represented by VLspa and VLspb, respectively, then two of the four consecutive vertical scanning periods are the first polarity periods and the other two vertical scanning periods are the second polarity periods.
  • values of one of the two vertical scanning periods thereof are equal to those of the other vertical scanning period.
  • is equal to that of vertical scanning periods that satisfy
  • the plurality of the pixels are arranged in column and row directions so as to form a matrix pattern, and in each of the plurality of the pixels, the first and second subpixels are arranged in the column direction.
  • voltages applied to the first and second subpixel electrodes change as voltages on their associated storage capacitor lines vary.
  • a voltage on a storage capacitor line associated with the first subpixel electrode and a voltage on a storage capacitor line associated with the second subpixel electrode change mutually differently.
  • a voltage applied to the second subpixel electrode of a particular one of the plurality of the pixels and a voltage applied to the first subpixel electrode of another pixel that is adjacent to the particular pixel in the column direction change as the voltage on their common storage capacitor line varies.
  • a voltage applied to the second subpixel electrode of a particular one of the plurality of the pixels and a voltage applied to the first subpixel electrode of another pixel that is adjacent to the particular pixel in the column direction change as voltages on their associated storage capacitor lines vary.
  • the first and second subpixel electrodes are connected to the same signal line by way of their associated switching element.
  • the first and second subpixel electrodes are respectively connected to first and second signal lines by way of first and second switching elements, respectively.
  • one of the two vertical scanning periods satisfies
  • and the other vertical scanning period satisfies
  • the frame frequency is 60 Hz.
  • the frame frequency is 120 Hz.
  • one of the two vertical scanning periods satisfies
  • and the other vertical scanning period satisfies
  • VLspa is equal to VLspb in each of the two vertical scanning periods.
  • voltages on storage capacitor lines associated with the first and second subpixel electrodes change between a first level, a second level that is higher than the first level, and a third level that is higher than the second level.
  • the first and second subpixel electrodes have the same display area.
  • the present invention provides a liquid crystal display device that can minimize the occurrence of reliability problems such as non-smoothness of image displayed or residual images.
  • FIG. 1 illustrates the liquid crystal display device 100 of this preferred embodiment.
  • the liquid crystal panel 100A of the liquid crystal display device 100 includes a display section 110 in which a number of pixels are arranged in columns and rows to define a matrix pattern and a driver 120 for driving the display section 110 as shown in FIG. 2 .
  • each pixel includes a liquid crystal layer and a plurality of electrodes for applying a voltage to the liquid crystal layer.
  • the driver 120 generates a drive signal based on an input video signal.
  • FIG. 3(a) is a schematic plan view illustrating the electrode structure of a single pixel
  • FIG. 3(b) is a schematic cross-sectional view of a single subpixel as viewed on the plane 3B-3B' shown in FIG. 3(a)
  • each pixel 10 includes first and second subpixels 10a and 10b that are arranged in the column direction.
  • 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 with the liquid crystal layer 13 interposed between them.
  • FIG. 3(b) illustrates the configuration of only the first subpixel 10a
  • the second subpixel 10b has the same configuration as the one illustrated in FIG. 3(b)
  • the counter electrode 17 is typically provided as a single common electrode for every pixel 10.
  • mutually different voltages are applicable to the first and second subpixel electrodes 18a and 18b, thus making the effective voltage applied to the liquid crystal layer of the first subpixel 10a different from the one applied to that of the second subpixel 10b.
  • each pixel is supposed to display a predetermined grayscale tone for several frames on end for the sake of simplicity.
  • the reference numerals 1 through 6 denote respective vertical scanning periods.
  • one "vertical scanning period" is defined to be an interval between a point in time when one scan line is selected to write a display signal voltage and a point in time when that scan line is selected to write the next display signal voltage.
  • each of one frame period of a non-interlaced drive input video signal and one field period of an interlaced drive input video signal will be referred to herein as "one vertical scanning period of the input video signal".
  • one vertical scanning period of a liquid crystal display device corresponds to one vertical scanning period of the input video signal.
  • one vertical scanning period of the liquid crystal panel is supposed to correspond to that of the input video signal for the sake of simplicity.
  • the present invention is in no way limited to that specific preferred embodiment.
  • the present invention is also applicable to a so-called "2x drive" with a vertical scanning frequency of 120 Hz in which two vertical scanning periods of the liquid crystal panel (that lasts 2 ⁇ 1/120 sec, for example) are allocated to one vertical scanning period of the input video signal (that lasts 1/60 sec, for example). Also, in this example, the lengths of the respective vertical scanning periods are supposed to be equal to each other. Furthermore, in each vertical scanning period, the interval between a point in time when one scan line is selected and a point in time when the next scan line is selected will be referred to herein as one horizontal scanning period (1H).
  • the upper and lower rectangles represent the first and second subpixels, respectively. Of these two subpixels, the one with the higher luminance is plain, while the other with the lower luminance is shadowed.
  • "+" and "-” represent the polarities of the display signal voltages when the associated scan line is selected with respect to the common voltage applied to the counter electrode. In this case, "+” indicates that the potential at the first and second subpixel electrodes is higher than the one at the counter electrode and that the electric field is directed from the subpixel electrodes toward the counter electrode.
  • "-" indicates that the potential at the first and second subpixel electrodes is lower than the one at the counter electrode and that the electric field is directed from the counter electrode toward the subpixel electrodes.
  • “+” and “-” will be referred to herein as a “first polarity” and a “second polarity”, respectively, and will also be collectively referred to herein as “polarities”.
  • a period with the "+” polarity and a period with the "-” polarity will be referred to herein as a "first polarity period” and a “second polarity period”, respectively.
  • the first, third and fifth periods are first polarity periods
  • the second, fourth and sixth periods are second polarity periods
  • the polarity inverts every vertical scanning period in the liquid crystal display device disclosed in Patent Document No. 1.
  • the first subpixel in any of the first through sixth periods, has a higher luminance than the second subpixel in the device of Patent Document No. 1.
  • Portions (b) and (c) of FIG. 4 show the effective voltages VLspa and VLspb that are applied to the respective liquid crystal layers of the first and second subpixels in the respective vertical scanning periods in the liquid crystal display device of Patent Document No. 1. The levels of these voltages are indicated by the bold lines.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels are the effective values of the differences between the voltages applied to the first and second subpixel electrodes and the voltage Vc applied to the counter electrode.
  • the voltage Vc applied to the counter electrode is shown as being constant.
  • the voltages applied to the respective liquid crystal layers of the first and second subpixels may also be changed within the same vertical scanning period by varying the voltage on the storage capacitor line as disclosed in Patent Document No. 1.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the first period is a first polarity period and the first subpixel is brighter than the second subpixel.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels change.
  • the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the second period is a second polarity period and the first subpixel is brighter than the second subpixel.
  • the first, third and fifth periods are also first polarity periods
  • the second, fourth and sixth periods are second polarity periods
  • the luminance of the first subpixel is higher than that of the second subpixel in the first, third and fifth periods but the luminance of the second subpixel is higher than that of the first subpixel in the second, fourth and sixth periods.
  • Portions (b) and (c) of FIG. 5 show the effective voltages VLspa and VLspb that are applied to the respective liquid crystal layers of the first and second subpixels in the respective vertical scanning periods. The levels of these voltages are indicated by the bold lines. Although not shown in portions (b) and (c) of FIG. 5 , the voltages applied to the respective liquid crystal layers of the first and second subpixels may also be changed within the same vertical scanning period by varying the voltage on the storage capacitor line as disclosed in Patent Document No. 1.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the first period is a first polarity period and the first subpixel is brighter than the second subpixel.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels change.
  • the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the second period is a second polarity period and the second subpixel is brighter than the first subpixel.
  • the first subpixel is sometimes brighter, but sometimes less bright, than the second subpixel unlike the liquid crystal display device disclosed in Patent Document No. 1. Consequently, the degree of non-smoothness on the screen can be reduced.
  • the period in which the first subpixel is brighter than the second subpixel is always the first polarity period and the period in which the second subpixel is brighter than the first subpixel is always the second polarity period.
  • the average of the effective voltages VLspa applied to the liquid crystal layer of the first subpixel over multiple vertical scanning periods is higher than the voltage Vc applied to the counter electrode
  • the average of the effective voltages VLspb applied to the liquid crystal layer of the second subpixel over multiple vertical scanning periods is lower than the voltage Vc applied to the counter electrode.
  • the first, second, fifth and sixth periods are first polarity periods, while the third and fourth periods are second polarity periods.
  • the first polarity period is a period in which the voltages applied to the first and second subpixel electrodes are higher than the one applied to the counter electrode
  • the second polarity period is a period in which the voltages applied to the first and second subpixel electrodes are lower than the one applied to the counter electrode.
  • two out of the four periods are first polarity periods and the other two are second polarity periods.
  • the first and second periods are first polarity periods and the third and fourth periods are second polarity periods.
  • Portions (b) and (c) of FIG. 6 show the effective voltages VLspa and VLspb that are applied to the respective liquid crystal layers of the first and second subpixels in the respective vertical scanning periods. The levels of these voltages are indicated by the bold lines.
  • the voltages applied to the respective liquid crystal layers of the first and second subpixels may also be changed within the same vertical scanning period by varying the voltage on the storage capacitor line just as disclosed in Patent Documents Nos. 1 and 2.
  • the voltage Vc applied to the counter electrode is used as a reference voltage in portions (b) and (c) of FIG. 6 , the voltage Vc applied to the counter electrode is illustrated as being constant irrespective of time. However, the voltage Vc applied to the counter electrode may also vary with time.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the first period is a first polarity period and the first subpixel is brighter than the second subpixel.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels change.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the second period is a first polarity period and the second subpixel is brighter than the first subpixel.
  • the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the third period is a second polarity period and the first subpixel is brighter than the second subpixel.
  • the fourth period the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the fourth period is a second polarity period and the second subpixel is brighter than the first subpixel.
  • two out of four consecutive vertical scanning periods are first polarity periods, one of which satisfies
  • the two other ones of the four consecutive vertical scanning periods are second polarity periods, one of which satisfies
  • the brightness levels of the subpixels are inverted every vertical scanning period and the polarity is inverted every other vertical scanning period.
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B(right), +), (D(ark), +), (B, -) and (D, -)
  • the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (B, +), (D, -) and (B, -)
  • "B" indicates that the pixel is brighter than the other pixel
  • "D" indicates that the pixel is darker than the other.
  • the difference between the average of the effective voltage applied to the liquid crystal layer of the first subpixel and that of the effective voltages applied to that of the second subpixel in each of the first and second polarity periods becomes substantially equal to zero.
  • each pair of first and second polarity periods has a period that satisfies
  • the average of the effective voltages VLspa and that of the effective voltages VLspb over multiple vertical scanning periods can be both equal to zero. Furthermore, even if the averages of the effective voltages VLspa and VLspb do not become equal to zero, the averages of the effective voltages VLspa and VLspb can be both controlled to zero by adjusting the counter voltage because the average of the effective voltages VLspa is approximately equal to that of the effective voltages VLspb. By controlling the averages of the effective voltages to zero in this manner, the residual image and other reliability-related problems can be overcome. It should be noted that various configurations could be used to apply mutually different voltages to the respective liquid crystal layers of the first and second subpixels such that the relations described above are satisfied.
  • This preferred embodiment is preferably applied to a liquid crystal display device that uses a vertical alignment liquid crystal layer including a nematic liquid crystal material with negative dielectric anisotropy.
  • the liquid crystal layer of each subpixel preferably has four domains in which the liquid crystal molecules tilt in respective azimuth directions that are different from each other by approximately 90 degrees under a voltage applied (i.e., may operate in the MVA mode).
  • the liquid crystal layer of each subpixel may also have axisymmetric alignment at least when a voltage is applied thereto (i.e., may operate in the ASM mode).
  • the liquid crystal display device 100 includes a liquid crystal panel 100A, a pair of phase compensators (typically phase plates) 20a and 20b arranged on both sides of the liquid crystal panel 100A, a pair of polarizers 30a and 30b arranged to sandwich these members between them, and a backlight 40.
  • the polarizers 30a and 30b are arranged as crossed Nicols such that their axes of transmission (which will also be referred to herein as "axes of polarization”) cross each other at right angles. While no voltage is applied to the liquid crystal layer 13 of the liquid crystal panel 100A (see FIG. 3(b) ), i.e., in a vertical alignment state, this device conducts black display.
  • this liquid crystal display device 100 is a normally black mode liquid crystal display device.
  • the phase compensators 20a and 20b are provided to improve the viewing angle characteristic of the liquid crystal display device and may be designed as best ones by known technologies. Specifically, the phase compensators 20a and 20b may be optimized such that the difference in luminance between when the image is viewed obliquely and when the image is viewed straight in the black display mode (i.e., the difference in black luminance) is minimized in every azimuth direction.
  • a scan line 12 is arranged between the first and second subpixel electrodes 18a and 18b.
  • scan lines 12, signal lines, TFTs (not shown in FIG. 3 ) and circuits for driving them are arranged on the substrate 11a to apply predetermined voltages to the first and second subpixel electrodes 18a and 18b at prescribed timings.
  • color filters and other members are arranged as needed.
  • the subpixel electrode 18a on the glass substrate 11a has a slit 18s, and the subpixel electrode 18a and the counter electrode 17 together generate an oblique electric field in the liquid crystal layer 13.
  • the liquid crystal layer 13 On the other hand, on the surface of the glass substrate 11b with the counter electrode 17, arranged are ribs 19 that protrude toward the liquid crystal layer 13, which is made of a nematic liquid crystal material with negative dielectric anisotropy.
  • the liquid crystal layer 13 exhibits a substantially vertically aligned state when no voltages are applied thereto. That is to say, the vertically aligned liquid crystal molecules can be tilted toward a predetermined direction with stability by using the sloped side surfaces of the ribs 19 and the oblique electric field in combination.
  • the ribs 19 have sloped side surfaces that are raised toward their center, and the liquid crystal molecules are aligned substantially perpendicularly to those tilted side surfaces. Consequently, the ribs 19 produce a distribution of tilt angles of the liquid crystal molecules.
  • the tilt angle of a liquid crystal molecule means the angle defined by the long axis of the molecules with respect to the surface of the substrate.
  • the slit 18s changes the directions of the electric field applied to the liquid crystal layer regularly. Due to the combined effects of these ribs 19 and the slit 18s, when an electric field is applied, the liquid crystal molecules are aligned in the four directions indicated by the arrows in FIG.
  • the rectangular display area of the liquid crystal panel 100A is typically arranged such that its longitudinal direction is defined horizontally and the transmission axis of the polarizer 30a is defined to be parallel to the longitudinal direction.
  • the pixels 10 are arranged such that the longitudinal direction of the pixels 10 intersects with that of the liquid crystal panel 100A at right angles.
  • the first and second subpixels 10a and 10b preferably have the same area.
  • Each of these subpixels preferably has a first rib that runs in a first direction and a second rib that runs in a second direction that intersects with the first direction substantially at right angles, and the first and second ribs are preferably arranged symmetrically to each other within each subpixel with respect to a centerline that is defined parallel to the scan line 12.
  • the arrangement of the ribs in one of the two subpixels and that of the ribs in the other subpixel are preferably symmetrical to each other with respect to a centerline that is drawn perpendicularly to the scan line 12.
  • the liquid crystal molecules are aligned upper rightward, upper leftward, lower rightward and lower leftward within each subpixel and the respective liquid crystal domains come to have substantially the same area in the entire pixel including the first and second subpixels.
  • a good viewing angle characteristic that is symmetrical both vertically and horizontally is realized. This effect is achieved particularly significantly when a pixel has a small area.
  • it is preferred to adopt a configuration in which the interval between the respective centerlines of the two subpixels that are drawn parallel to the scan line is approximately equal to a half of the arrangement pitch of the scan lines.
  • each pixel 10 in the liquid crystal display device 100 of this preferred embodiment and application of mutually different voltages to the respective liquid crystal layers of the two subpixels 10a and 10b included in this pixel 10 will be described with reference to FIGS. 7 through 9 .
  • the pixel 10 includes two subpixels 10a and 10b.
  • the gate electrodes of the TFTs 16a and 16b are both connected to the same scan line 12.
  • the source electrodes of the TFTs 16a and 16b are connected to the same signal line 14.
  • the storage capacitors 22a and 22b are connected to their associated storage capacitor lines (CS bus lines) 24a and 24b, respectively.
  • the storage capacitor 22a includes a storage capacitor electrode that is electrically connected to the subpixel electrode 18a, a storage capacitor counter electrode that is electrically connected to the storage capacitor line 24a, and an insulating layer (not shown) arranged between the electrodes.
  • the storage capacitor 22b includes a storage capacitor electrode that is electrically connected to the subpixel electrode 18b, a storage capacitor counter electrode that is electrically connected to the storage capacitor line 24b, and an insulating layer (not shown) arranged between the electrodes.
  • the respective storage capacitor counter electrodes of the storage capacitors 22a and 22b are independent of each other and can receive mutually different storage capacitor counter voltages from the storage capacitor lines 24a and 24b, respectively.
  • FIG. 8 schematically shows the equivalent circuit of one pixel 10 of the liquid crystal display device 100.
  • the liquid crystal layers of the subpixels 10a and 10b are identified by the reference numerals 13a and 13b, respectively.
  • a liquid crystal capacitor formed of the subpixel electrode 18a, the liquid crystal layer 13a, and the counter electrode 17 will be identified by Clca.
  • a liquid crystal capacitor formed of the subpixel electrode 18b, the liquid crystal layer 13b, and the counter electrode 17 will be identified by Clcb.
  • the same counter electrode 17 is shared by these two subpixels 10a and 10b.
  • the liquid crystal capacitors Clca and Clcb are supposed to have the same electrostatic capacitance CLC (V).
  • CLC (V) depends on the effective voltages (V) applied to the liquid crystal layers of the respective subpixels 10a and 10b.
  • the storage capacitors 22a and 22b that are connected independently of each other to the liquid crystal capacitors of the respective subpixels 10a and 10b will be identified herein by Ccsa and Ccsb, respectively, which are supposed to have the same electrostatic capacitance CCS.
  • one electrode of the liquid crystal capacitor Clca and one electrode of the storage capacitor Ccsa are connected to the drain electrode of the TFT 16a, which functions as a switching element for the subpixel 10a.
  • the other electrode of the liquid crystal capacitor Clca is connected to the counter electrode 17.
  • the other electrode of the storage capacitor Ccsa is connected to the storage capacitor line 24a.
  • one electrode of the liquid crystal capacitor Clcb and one electrode of the storage capacitor Ccsb are connected to the drain electrode of the TFT 16b, which functions as a switching element for the subpixel 10b.
  • the other electrode of the liquid crystal capacitor Clcb is connected to the counter electrode 17.
  • the other electrode of the storage capacitor Ccsb is connected to the storage capacitor line 24b.
  • the gate electrodes of the TFTs 16a and 16b are both connected to the scan line 12 and the source electrodes thereof are both connected to the signal line 14.
  • FIG. 9 schematically shows how the respective voltages that are applied to drive the liquid crystal display device 100 of this preferred embodiment vary within a vertical scanning period.
  • Vs represents the voltage on the signal line 14
  • Vcsa represents the voltage on the storage capacitor line 24a
  • Vcsb represents the voltage on the storage capacitor line 24b
  • Vg represents the voltage on the scan line 12
  • Vlca represents the voltage to the first subpixel electrode 18a
  • Vlcb represents the voltage to the second subpixel electrode 18b.
  • the dashed line indicates the voltage COMMON (Vc) to the counter electrode 17.
  • the voltage Vcsa on the storage capacitor line 24a varies periodically within the range of Vc - Vad to Vc + Vad.
  • the voltage Vcsb on the storage capacitor line 24b also varies periodically within the range of Vc - Vad to Vc+ Vad.
  • the waveform of the voltage Vcsb on the storage capacitor line 24b has a phase that is different by 180 degrees from that of the voltage Vcsa on the storage capacitor line 24a.
  • the voltage Vg on the scan line 12 rises from VgL to VgH to turn the TFTs 16a and 16b ON simultaneously.
  • the voltage Vs on the signal line 14 is transmitted to the subpixel electrodes 18a and 18b of the subpixels 10a and 10b to charge the liquid crystal capacitors Clca and Clcb of the subpixels 10a and 10b.
  • the storage capacitors Csa and Csb of the respective subpixels are also charged with the voltage on the signal line 14.
  • the voltage Vg on the scan line 12 falls from VgH to VgL to turn the TFTs 16a and 16b OFF simultaneously and electrically isolate the liquid crystal capacitors Clca and Clcb of the subpixels 10a and 10b and the storage capacitors Ccsa and Ccsb from the signal line 14.
  • Vlca Vs - Vd + 2 ⁇ K ⁇ Vad
  • the voltage Vcsa on the storage capacitor line 24a falls from Vc+Vad to Vc - Vad and the voltage Vcsb on the storage capacitor line 24b rises from VcVad to Vc+Vad. That is to say, these voltages Vcsa and Vcsb both change twice as much as Vad again.
  • the voltage Vcsa on the storage capacitor line 24a rises from Vc - Vad to Vc + Vad and the voltage Vcsb on the storage capacitor line 24b falls from Vc + Vad to Vc - Vad. That is to say, these voltages Vcsa and Vcsb both change twice as much as Vad again.
  • Vlcb Vs - Vd - 2 ⁇ K ⁇ Vad respectively.
  • the voltages Vcsa, Vcsb, Vlca and Vlcb alternate their levels at the times T4 and T5.
  • the alternation interval between T4 and T5 may be appropriately determined to be one, two, three or more times as long as 1H according to the driving method of the liquid crystal display device (such as the polarity inversion method) or the display state (such as the degree of flicker or non-smoothness of the image displayed). This alternation is continued until the pixel 10 is rewritten next time, i.e., until the current time becomes equivalent to T1.
  • Vlcb Vs - Vd + K ⁇ Vad
  • Vlcb Vs - Vd - K ⁇ Vad respectively.
  • V1 VLspa
  • V2 VLspb
  • V ⁇ 1 Vs - Vd + K ⁇ Vad - Vc
  • V ⁇ 2 Vs - Vd - K ⁇ Vad - Vc respectively.
  • FIG. 10 schematically shows the relation between V1 and V2 in the liquid crystal display device 100 of this preferred embodiment.
  • the smaller the V1 value the bigger ⁇ V in the liquid crystal display device 100 of this preferred embodiment.
  • the ⁇ V value varies with V1 or V2 because the static capacitance CLC(V) of the liquid crystal capacitor varies with the voltage.
  • FIG. 11(a) shows the ⁇ characteristic of the liquid crystal display device 100 of this preferred embodiment at a right 60 degree viewing angle
  • FIG. 11(b) shows the ⁇ characteristic of the liquid crystal display device 100 of this preferred embodiment at an upper right 60 degree viewing angle
  • FIGS. 11(a) and 11(b) also show the ⁇ characteristics that were observed when the same voltage was applied to the subpixels 10a and 10b for the purpose of comparison. As can be seen from FIGS.
  • the respective voltages as shown in FIG. 9 within a single vertical scanning period, mutually different effective voltages are applicable to the respective liquid crystal layers of different subpixels, and the ⁇ characteristic in an oblique viewing direction is improved as a result.
  • Vg represents the voltage on the scan line 12
  • Vcsa and Vcsb represent the voltages on the first and second storage capacitor lines 24a and 24b, respectively
  • VLspa and VLspb represent the effective voltages applied to the respective liquid crystal layers 13a and 13b of the first and second subpixel electrodes 10a and 10b.
  • one vertical scanning period is an interval between a point in time when a scan line is selected and a point in time when the next scan line is selected, and is represented by V-Total in FIG. 12 . It should be noted that the variation in the voltage Vd caused by the feedthrough phenomenon that has already been described with reference to FIG. 9 is not shown in FIG. 12 .
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines each have display periods AH and regulation periods BH.
  • Each of these voltages Vcsa and Vcsb on the first and second storage capacitor lines varies periodically in different cycles through the display and regulation periods AH and BH.
  • the voltages Vcsa and Vcsb vary in regular cycles of 20H through the display periods AH and in different regular cycles of either 36H or 26H through the regulation periods BH.
  • the sum of one display period AH and one regulation period BH is equal to one vertical scanning period (V-Total).
  • the display period AH begins when the voltages Vcsa and Vcsb on the first and second storage capacitor lines change after a vertical scanning period for a certain frame has started.
  • the regulation period BH ends when the voltages Vcsa and Vcsb on the first and second storage capacitor lines change after the vertical scanning period for that frame has terminated.
  • the frame frequency may be 60 Hz, for example.
  • FIG. 12 shows how the voltages change through four vertical scanning periods.
  • those four vertical scanning periods will be referred to herein as first, second, third and fourth vertical scanning periods, respectively
  • the display periods AH and regulation periods BH associated with those vertical scanning periods will be referred to herein as first, second, third and fourth display periods AH and first, second, third and fourth regulation periods BH, respectively.
  • the voltage Vcsa on the storage capacitor line 24a rises to a higher voltage VcH
  • the voltage Vcsb on the storage capacitor line 24b falls to a lower voltage VcL.
  • Vcsb rises to a higher voltage VcH.
  • the difference between VcH and VcL is equal to 2 ⁇ Vad that has already been described with reference to FIG. 9 .
  • the voltage Vg on the scan line 12 changes from VgL into VgH.
  • the first vertical scanning period begins and the first and second subpixel electrodes 18a and 18b are charged.
  • the voltage Vg on the scan line 12 is VgH
  • the voltage Vs on the signal line 14 is higher than the voltage Vc at the counter electrode 17. That is why as a result of the charge, the voltages at the first and second subpixel electrodes 18a and 18b become higher than the voltage Vc at the counter electrode 17.
  • the first and second subpixel electrodes 18a and 18b finish being charged.
  • the voltage Vcsa on the first storage capacitor line 24a rises to VcH and the voltage Vcsb on the second storage capacitor line 24b falls to VcL.
  • the first display period AH it is when the voltage Vcsa on the first storage capacitor line 24a increases and the voltage Vcsb on the second storage capacitor line 24b decreases that the first display period AH begins.
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b increase or decrease every 10H period and vary periodically in regular cycles of 20H.
  • the first regulation period BH begins.
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b increase or decrease every 18H period.
  • the voltages at the first and second subpixel electrodes 18a and 18b change as the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b vary. That is why in the first vertical scanning period, the absolute value of the effective voltage applied to the liquid crystal layer 13a of the first subpixel 10a becomes greater than that of the effective voltage applied to the liquid crystal layer 13b of the second subpixel 10b and the first subpixel 10a becomes brighter than the second subpixel 10b.
  • the voltage Vg on the scan line 12 changes from VgL into VgH.
  • the first vertical scanning period ends and the second vertical scanning period begins and the first and second subpixel electrodes 18a and 18b are charged.
  • the voltage Vg on the scan line 12 is VgH
  • the voltage Vs on the signal line 14 is higher than the voltage Vc at the counter electrode 17. That is why as a result of the charge, the voltages at the first and second subpixel electrodes 18a and 18b become higher than the voltage Vc at the counter electrode 17.
  • the first and second subpixel electrodes 18a and 18b finish being charged.
  • the voltage Vcsa on the first storage capacitor line 24a falls to VcL and the voltage Vcsb on the second storage capacitor line 24b rises to VcH.
  • the first regulation period ends and the second display period AH begins.
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b also increase or decrease every 10H period and vary periodically in regular cycles of 20H.
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b will increase or decrease every 13H period.
  • the voltages at the first and second subpixel electrodes 18a and 18b change as the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b vary. That is why in the second vertical scanning period, the absolute value of the effective voltage applied to the liquid crystal layer 13b of the second subpixel 10b becomes greater than that of the effective voltage applied to the liquid crystal layer 13a of the first subpixel 10a and the second subpixel 10b becomes brighter than the first subpixel 10a.
  • the voltage Vg on the scan line 12 changes from VgL into VgH.
  • the second vertical scanning period ends and the third vertical scanning period begins and the first and second subpixel electrodes 18a and 18b are charged. While the voltage Vg on the scan line 12 is VgH, the voltage Vs on the signal line 14 is lower than the voltage Vc at the counter electrode 17.
  • the voltages at the first and second subpixel electrodes 18a and 18b become lower than the voltage Vc at the counter electrode 17. Thereafter, when the voltage Vg on the scan line 12 falls from VgH to VgL again, the first and second subpixel electrodes 18a and 18b finish being charged.
  • the voltage Vcsa on the first storage capacitor line 24a falls to VcL and the voltage Vcsb on the second storage capacitor line 24b rises to VcH.
  • the second regulation period BH ends and the third display period AH begins.
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b also increase or decrease every 10H period and vary periodically in regular cycles of 20H.
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b will increase or decrease every 18H period.
  • the voltages at the first and second subpixel electrodes 18a and 18b change as the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b vary. That is why in the third vertical scanning period, the absolute value of the effective voltage applied to the liquid crystal layer 13a of the first subpixel 10a becomes greater than that of the effective voltage applied to the liquid crystal layer 13b of the second subpixel 10b and the first subpixel 10a becomes brighter than the second subpixel 10b.
  • the third regulation period BH at a time when the voltage Vcsa on the first storage capacitor line 24a is VcL and when the voltage Vcsb on the second storage capacitor line 24b is VcH, the voltage Vg on the scan line 12 changes from VgL into VgH.
  • the third vertical scanning period ends and the fourth vertical scanning period begins and the first and second subpixel electrodes 18a and 18b are charged. While the voltage Vg on the scan line 12 is VgH, the voltage Vs on the signal line 14 is lower than the voltage Vc at the counter electrode 17.
  • the voltages at the first and second subpixel electrodes 18a and 18b become lower than the voltage Vc at the counter electrode 17. Thereafter, when the voltage Vg on the scan line 12 falls from VgH to VgL again, the first and second subpixel electrodes 18a and 18b finish being charged.
  • the voltage Vcsa on the first storage capacitor line 24a rises to VcH and the voltage Vcsb on the second storage capacitor line 24b falls to VcL.
  • the voltage Vcsa on the first storage capacitor line 24a increases and the voltage Vcsb on the second storage capacitor line 24b decreases that the third regulation period BH ends and the fourth display period AH begins.
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b also increase or decrease every 10H period and vary periodically in regular cycles of 20H.
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b will increase or decrease every 13H period.
  • the voltages at the first and second subpixel electrodes 18a and 18b change as the voltages Vcsa and Vcsb on the first and second storage capacitor lines 24a and 24b vary. That is why in the fourth vertical scanning period, the absolute value of the effective voltage applied to the liquid crystal layer 13b of the second subpixel 10b becomes greater than that of the effective voltage applied to the liquid crystal layer 13a of the first subpixel 10a and the second subpixel 10b becomes brighter than the first subpixel 10a. From the fifth vertical scanning period on, the respective voltages will vary in quite the same way as in the first through fourth vertical scanning periods shown in FIG. 12 .
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B, +), (D, +), (B, -) and (D, -), while the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (B, +), (D, -) and (B, -). That is to say, the brightness levels and polarities of the first and second subpixels change just as shown in portion (a) of FIG. 6 .
  • the voltages Vcsa and Vcsb on the first and second storage capacitor lines in this manner, the deterioration of display quality can be minimized in a liquid crystal display device, of which the ⁇ characteristic has reduced viewing angle dependence.
  • the liquid crystal display device of this preferred embodiment is designed such that the potentials at the pixel electrode and at the counter electrode switch their levels at regular intervals and that the direction of the electric field applied to the liquid crystal layer is also inverted at regular intervals.
  • the directions of the electric field applied to the liquid crystal layer change from toward the light source side into toward the viewer side, and vice versa.
  • Such a drive method that sets an alternating current voltage is called an "AC drive method”.
  • the inversion interval of the direction of the electric field applied to the liquid crystal layer may be 66.667 ms, which is twice as long as two frame periods of 33.333 ms, for example. That is to say, in the liquid crystal display device of this preferred embodiment, the direction of the electric field applied to the liquid crystal layer is inverted every time two frame pictures are presented. That is why in presenting a still picture, unless the electric field strengths (i.e., the magnitudes of applied voltages) exactly matched with each other in respective electric field directions (i.e., if the electric field intensities changed every time the directions of the electric field change), the pixel luminances would change and a flicker would be produced on the screen whenever the electric field intensities change.
  • the electric field strengths i.e., the magnitudes of applied voltages
  • the electric field intensities (or the magnitudes of applied voltages) in the respective electric field directions need to be exactly matched with each other.
  • the flicker is reduced by arranging pixels with mutually different electric field directions adjacent to each other within a display area and spatially averaging the luminances of those pixels.
  • Such a method is generally called either a "dot inversion” or a "line inversion”.
  • inversion drive methods that include not just a method in which the polarities of those pixels are inverted in a checkered pattern on a pixel-by-pixel basis (i.e., the polarities are inverted both every row and every column, which is a so-called “dot inversion drive”) and a method in which the polarities are inverted on a line-by-line basis (i.e., the polarities are inverted every row, which is a so-called “line inversion drive”) but also a method in which the polarities are inverted every other row and every column (which is a so-called “two-row, one-column dot inversion drive”). And an appropriate one of those methods is selected as needed.
  • the absolute values of the effective voltages applied to the liquid crystal layer should agree with each other as closely as possible. That is to say, as in resolving the reliability-related problem described above, the average of the voltages applied to the liquid crystal layer should be as close to zero as possible.
  • pixels among which the electric field is applied to the liquid crystal layer in respectively different directions in each frame period, should be arranged adjacent to each other.
  • a third condition is that one type of subpixels that are brighter than subpixels of the other type be arranged as randomly as possible within the same frame.
  • those subpixels are preferably arranged such that the one type of subpixels, which are brighter than the subpixels of the other type, are adjacent to each other in neither the column direction nor the row direction.
  • the one type of subpixels that are brighter than the other type are preferably arranged in a checkered pattern.
  • the liquid crystal display device of this preferred embodiment satisfies these three conditions. But before describing exactly how the device satisfies those conditions, it will be described with reference to FIGS. 13 and 14 that the liquid crystal display device 100 of this preferred embodiment has a pixel arrangement that can be used effectively to get the one-dot inversion drive done with those conditions satisfied.
  • FIG. 13 illustrates an equivalent circuit of the liquid crystal display device 100.
  • each pixel is supposed to have the structure shown in FIGS. 7 and 8 . Those pixels are arranged in a matrix pattern.
  • pixel n-m a pixel located at an n th row and an m th column
  • subpixel n-m-A subpixel n-m-A
  • subpixel n-m-B subpixel n-m-B
  • the liquid crystal display device 100 includes ten storage capacitor trunks CS1 through CS10, and each subpixel is connected to one of those storage capacitor trunks CS1 through CS10 by way of a storage capacitor line (CS bus line).
  • CS bus line a storage capacitor line
  • the storage capacitor trunk CS2 is connected to subpixels 1-a-B, 1-b-B, 1-c-B, etc. on the first pixel row and to subpixels 2-a-A, 2-b-A, 2-c-A, etc. on the second pixel row.
  • each subpixel and another subpixel included in a different pixel that is adjacent to the former subpixel are connected to the same storage capacitor trunk by way of the same storage capacitor line.
  • the first and second subpixels 1-a-A and 1-a-B include liquid crystal capacitors CLC1-a-A and CLC1-a-B and storage capacitors CCS1-a-A and CCS1-a-B, respectively.
  • Each of the liquid crystal capacitors is formed by a subpixel electrode, the counter electrode ComLC and the liquid crystal layer interposed between them.
  • Each of the storage capacitors is formed by a storage capacitor electrode, an insulating film and a storage capacitor counter electrode ComCS1 or ComCS2.
  • the first and second subpixels 1-a-A and 1-a-B are connected in common to the same signal line Sa by way of their associated TFTs 1-a-A and 1-a-B, respectively.
  • the TFTs 1-a-A and 1-a-B have their ON/OFF states controlled with a voltage supplied onto their common signal line G1. And when these two TFTs are ON, voltages are applied through the same signal line Sa to the respective subpixel electrodes and respective storage capacitor electrodes of the first and second subpixels 1-a-A and 1-a-B.
  • the storage capacitor counter electrode of the subpixel 1-a-A is connected to the storage capacitor trunk CS1 by way of its associated storage capacitor line (CS bus line) CS1.
  • the storage capacitor counter electrode of the subpixel 1-a-B is connected to the storage capacitor trunk CS2 by way of its associated storage capacitor line (CS bus line) CS2.
  • CS bus line storage capacitor line
  • FIG. 14 shows the brightness levels and polarities of respective subpixels that have changed within the effective scanning period of a certain frame. Specifically, in FIG. 14 , illustrated are pixels on the first through twelfth rows and the a th through , f th columns.
  • FIG. 15 shows the waveforms of respective voltages (or signals) to drive a liquid crystal display device with the configuration shown in FIG. 13 . In FIG. 14
  • Vsa and Vsb represent the voltages on the signal lines Sa and Sb
  • Vg1 through Vg12 represent the voltages on the scan lines G1 through G12
  • Vcs1 through Vcs10 represent the voltages on the storage capacitor trunks CS1 through CS10
  • VLsp1-a-A through VLsp2-b-B represent the effective voltages applied to the liquid crystal layer of associated subpixels, respectively.
  • What is shown in FIG. 15 is voltage waveforms within one vertical scanning period.
  • the liquid crystal display device with the configuration shown in FIG. 13 is driven with voltages having the waveforms shown in FIG. 15 .
  • every pixel is supposed to display the same grayscale tone to avoid complicating the description excessively.
  • the voltages Vsa and Vsb on the signal lines Sa and Sb oscillate in regular cycles and with a predetermined amplitude as shown in FIG. 15 .
  • One cycle time of oscillation of these voltages Vsa and Vsb is two horizontal scanning periods (2H).
  • the voltage Vsb on the signal line Sb varies with a phase difference of 180 degrees with respect to the voltage Vsa on the signal line Sa.
  • a period in which the voltage Vsa or Vsb is higher than the voltage at the counter electrode is identified by "+” and a period in which the former is lower than the latter is identified by "-”.
  • a voltage on a signal line is transmitted to a subpixel electrode by way of one of the TFTs and then changes due to a variation in the voltage Vg on a scan line, thus producing a feedthrough phenomenon.
  • the voltage at the counter electrode is determined in view of this feedthrough phenomenon. Also, although not shown in FIG.
  • the voltages on other signal lines Sc and Se also vary in the same way as the voltage Vsa on the signal line Sa and the voltages on other signal lines Sd and Sf also vary in the same way as the voltage Vsb on the signal line Sb. Furthermore, as described above, an interval between a point in time when a voltage Vg on a certain scan line rises from Low level (VgL) to High level (VgH) and a point in time when the voltage Vg on the next scan line rises from VgL to VgH is one horizontal scanning period (1H).
  • the voltages Vcs1 through Vcs10 on the storage capacitor trunks CS1 through CS10 oscillate with the same amplitude and in the same regular cycles.
  • one oscillation cycle time is 20 H.
  • the voltages Vcs1 and Vcs2 have such a relation that if one of these two voltages changes into VcH, the other voltage will change into VcL and that if one of these two voltages changes into VcL, the other voltage will change into VcH.
  • the other four pairs of voltages Vcs3 and Vcs4, Vcs5 and Vcs6, Vcs7 and Vcs8, and Vcs9 and Vcs10 too have the same relation as that pair of voltages Vcs1 and Vcs2. Also, the voltages Vcs3 and Vcs4 change 2H after the voltages Vcs1 and Vcs2 have changed. In the same way, there is a time lag of 2H between the changes of the voltages Vcs5 and Vcs6, the voltages Vcs7 and Vcs8 and the voltages Vcs9 and Vcs10.
  • the voltages at the subpixels 1-a-A and 1-a-B change as an example.
  • the liquid crystal capacitors CLC1-a-A and CLC1-a-B of the subpixels 1-a-A and 1-a-B are charged. If the voltage Vg1 on the scan line G1 is VgH, the voltage Vsa on the signal line Sa is positive "+” and the liquid crystal capacitors CLC1-a-A and CLC1-a-B of the subpixels 1-a-A and 1-a-B are charged to a higher potential level than the one at the counter electrode.
  • the absolute value of the effective voltage applied to the liquid crystal layer of the subpixel 1-a-A that is electrically connected to the storage capacitor trunk CS1 becomes greater than that of the effective voltage applied to that of the subpixel 1-a-B that is electrically connected to the storage capacitor trunk CS2.
  • the effective voltage applied to the liquid crystal layer of that subpixel becomes higher than the voltage on its associated signal line when the voltage on its associated scan line is VgH.
  • the effective voltage applied to the liquid crystal layer of that subpixel becomes lower than the voltage on its associated signal line when the voltage on its associated scan line is VgH.
  • FIG. 14 shows the brightness levels and polarities of subpixels that have changed during the effective scanning period of a certain frame.
  • the sign "B" indicates that the given subpixel is brighter than the other subpixel (i.e., the absolute value of the effective voltage applied to the liquid crystal layer of that subpixel is greater than that of the effective voltage applied to the liquid crystal layer of the other).
  • the sign "D" indicates that the given subpixel is darker than the other subpixel (i.e., the absolute value of the effective voltage applied to the liquid crystal layer of that subpixel is smaller than that of the effective voltage applied to that of the other).
  • the sign "+” also indicates that the voltage at the subpixel electrode is higher than the one at the counter electrode and the sign "-" also indicates that the voltage at the subpixel electrode is lower than the one at the counter electrode.
  • Two subpixels included in each pixel are adjacent to a pixel with a smaller row number and a pixel with a bigger row number. In this example, of the two subpixels included in a single pixel, the subpixel adjacent to the pixel with the smaller row number will be identified herein by "A” and the subpixel adjacent to the pixel with the bigger row number will be identified herein by "B".
  • the brightness levels and polarities of the subpixels 1-a-A and 1-a-B included in the pixel 1-a will be described.
  • the voltage Vg1 on the scan line G1 is VgH
  • the voltage Vsa on the signal line Sa is higher than the voltage at the counter electrode. Therefore, the polarities of the subpixels 1-a-A and 1-a-B are both positive "+”.
  • the voltages Vcs1 and Vcs2 on the storage capacitor trunks CS1 and CS2 associated with the respective subpixels are as indicated by the leftmost arrows in FIG. 15 .
  • the brightness levels and polarities of subpixels 1-b-A and 1-b-B included in the pixel 1-b will be described. While the voltage Vg1 on the scan line G1 is VgH, the voltage Vsb on the signal line Sb is lower than the voltage at the counter electrode. Thus, the polarities of the subpixels 1-b-A and 1-b-B are both negative "-". On the other hand, when the voltage Vg1 on the scan line G1 changes from VgH into VgL, the voltages Vcs1 and Vcs2 on the storage capacitor trunks CS1 and CS2 associated with the respective subpixels 1-b-A and 1-b-B are as indicated by the leftmost arrows in FIG. 15 . That is why as can be seen from FIG.
  • the brightness levels and polarities of subpixels 2-b-A and 2-b-B included in the pixel 2-b will be described.
  • the voltage Vg2 on the scan line G2 is VgH
  • the voltage Vsb on the signal line Sb is higher than the voltage at the counter electrode.
  • the polarities of the subpixels 2-b-A and 2-b-B are both positive "+”.
  • the voltages Vcs2 and Vcs3 on the storage capacitor trunks CS2 and CS3 associated with the respective subpixels 2-b-A and 2-b-B are as indicated by the second leftmost arrows in FIG. 15 .
  • the liquid crystal display device of this preferred embodiment satisfies the three conditions mentioned above.
  • the liquid crystal display device of this preferred embodiment satisfies the first condition for the following reasons.
  • the liquid crystal display device of this preferred embodiment satisfies the first condition, i.e., the absolute values of the effective voltages applied to the liquid crystal layers of respective subpixels agree with each other in respective electric field directions.
  • each pixel includes two subpixels, of which the liquid crystal layers are supplied with mutually different effective voltages.
  • the brighter subpixel i.e., the subpixel marked "B" in FIG. 14
  • this first condition is imposed on the subpixels marked "B", in particular.
  • the first condition will be discussed with reference to the respective voltage waveforms shown in FIG. 15 , which shows the voltages VLsp1-a-A and VLsp2-a-A to be applied to the liquid crystal layers of the "B" subpixels 1-a-A and 2-a-A with mutually different electric field directions (or polarities).
  • the solid line represents the voltages applied to the subpixel electrodes of the subpixels 1-a-A and 2-a-A
  • the dashed line represents the voltage applied to the counter electrode.
  • the effective voltage applied to the liquid crystal layer is a difference between the voltages represented by the solid and dashed lines. That is why if the effective voltages applied to the liquid crystal layer in respective electric field directions (or the quantities of charge stored in the liquid crystal capacitors) are matched with each other as closely as possible by appropriately defining the voltage applied to the counter electrode, the first condition can be satisfied.
  • the liquid crystal display device of this preferred embodiment satisfies the second condition, i.e., pixels with mutually different polarities are arranged adjacent to each other in each frame period.
  • each pixel includes two subpixels, of which the liquid crystal layers are supplied with different effective voltages. That is why this second condition is imposed on not only on each pixel but also subpixels with the same effective voltage as well.
  • this second condition is particularly important for bright subpixels, i.e., the subpixels marked "B" in FIG. 14 , to satisfy this second condition as in the first condition described above.
  • the signs "+” and "-" representing the polarities (or electric field directions) of respective subpixels are inverted every other pixel (i.e., every second column) in the row direction (i.e., in the horizontal direction) in the order of (+, -), (+, -), (+, -), and so on, and also inverted every other pixel (i.e., every second row) in the column direction (i.e., in the vertical direction) in the order of (+, -), (+, -), (+, -), (+, -), and so on. That is to say, looking on a pixel-by-pixel basis, this device achieves the so-called “dot inversion" state, and therefore, satisfies the second condition.
  • the bright subpixels i.e., the subpixels marked "B” in FIG. 14
  • the bright subpixels i.e., the subpixels marked "B” in FIG. 14
  • the polarity of every "B" subpixel is positive "+”.
  • the device of this preferred embodiment satisfies the third condition.
  • multiple subpixels of which the luminance levels are intentionally different from each other, should be arranged such that subpixels with the same luminance level are adjacent to each other at as small a number of locations as possible.
  • FIG. 14 looking at a total of four subpixels that are arranged on two rows and two columns (e.g., the subpixels 1-a-A, 1-a-B, 1-b-A and 1-b-B), it can be seen that "B" and "D” subpixels are arranged in this order along the first column and then "D" and "B” subpixels are arranged in this order along the next column.
  • the liquid crystal display device of this preferred embodiment that has just been described with reference to FIGS. 14 and 15 satisfies all of the three conditions mentioned above, and therefore, realizes a display of quality images with a flicker eliminated.
  • FIGS. 14 and 15 The brightness levels and polarities of subpixels that have changed within the effective scanning period of a certain frame and the voltage waveforms are shown in FIGS. 14 and 15 .
  • the voltages on the signal lines change according to the waveforms shown in FIG. 15 with respect to the voltages on the scan lines but the voltages on the storage capacitor trunks change inversely to the waveforms shown in FIG. 15 . That is why in that frame, the polarities of the respective subpixels are the same as those of the subpixels shown in FIG. 14 but the brightness levels of the respective subpixels are inverted compared to the counterparts shown in FIG. 14 .
  • Vcs1 through Vcs6 represent the voltages on the storage capacitor trunks CS1 through CS6, Vg1 through Vg3 represent the voltages on the scan lines G1 through G3, and VLsp1-a-A through VLsp3-a-B represent the effective voltages applied to the respective liquid crystal layers of the subpixels 1-a-A through 3-a-B.
  • the four consecutive frames will be identified herein by n, n+1, n+2 and n+3, respectively.
  • FIG. 16 also shows vertical scanning periods of an input video signal.
  • Each vertical scanning period of the input video signal consists of an effective scanning period V-Disp during which pixels in the liquid crystal panel 100A (see FIG. 1 ) are selected on a row-by-row basis and a vertical-blanking interval V-Blank during which no pixels in the liquid crystal panel 100A are selected at all.
  • the duration of the effective scanning period is determined by the display area (or the number of rows of effective pixels) of the liquid crystal panel 100A.
  • the “vertical scanning period” refers to a “vertical scanning period of a liquid crystal panel”. That is to say, a “vertical scanning period” (i.e., a “vertical scanning period of the liquid crystal panel”) is used herein in a different sense from a “vertical scanning period of an input video signal".
  • a “vertical scanning period of an input video signal” is either a one-frame period or a one-field period, which begins and ends simultaneously for every pixel.
  • a “vertical scanning period” means an interval between a point in time when a scan line is selected to write a display signal voltage and a point in time when that scan line is selected to write the next display signal voltage as described above.
  • the vertical scanning periods start at different timing and end at different timing according to the associated scan line.
  • the oblique lines indicate that the start and end times of a vertical scanning period change according to the row of pixels selected.
  • scan lines are sequentially selected one after another from the first one.
  • a voltage applied to its associated subpixel electrode changes to start a vertical scanning period for that subpixel.
  • one vertical scanning period of an input video signal consists of an effective scanning period V-Disp and a vertical-blanking interval V-Blank.
  • the vertical scanning period of a certain subpixel begins in the middle of the effective scanning period of a frame n, continues through the vertical-blanking interval, and then ends halfway through the effective scanning period of the next frame n+1. After that, when its associated scan line is selected next time, the next vertical scanning period will begin for that subpixel.
  • the length of the "vertical scanning period" is equal to that of the "vertical scanning period of the input video signal”.
  • the (brightness, polarity) combinations of the subpixel 1-a-A change in the order of (B, +), (D, +), (B, -), and (D, - ); the (brightness, polarity) combinations of the subpixel 1-a-B change in the order of (D, +), (B, +), (D, -), and (B, -); the (brightness, polarity) combinations of the subpixel 2-a-A change in the order of (B, -), (D, -), (B, +), and (D, +); and the (brightness, polarity) combinations of the subpixel 2-a-B change in the order of (D, -), (B, -), (D, +), and (B, +) .
  • FIG. 17 shows the brightness levels and polarities of the subpixels 1-a-A and 1-a-B and the first change of voltages on the storage capacitor lines at the vertical scanning period of the subpixels 1-a-A and 1-a-B.
  • the polarity of the subpixels 1-a-A and 1-a-B is positive "+”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the subpixel 1-a-A is increase " ⁇ ”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the subpixel 1-a-B is decrease " ⁇ ".
  • the polarity of the subpixels 1-a-A and 1- a-B is positive "+"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the subpixel 1-a-A is decrease " ⁇ ”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the subpixel 1-a-B is increase " ⁇ ".
  • the polarity of the subpixels 1-a-A and 1-a-B is negative "-"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the subpixel 1-a-A is decrease " ⁇ ”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the subpixel 1-a-B is increase " ⁇ "
  • the polarity of the subpixels 1-a-A and 1-a-B is negative "-"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the subpixel 1-a-A is increase " ⁇ ”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the subpixel 1-a-B is decrease " ⁇ ".
  • the (polarity, first change of voltages on storage capacitor line) combinations of the subpixel 1-a-A from frame n through frame n+3 change (+, ⁇ ), (+, ⁇ ), (-, ⁇ ) and (-, ⁇ ) in this order. That is to say, mutually different combinations appear one after another.
  • the (polarity, first change of voltages on storage capacitor line) combinations of the subpixel 1-a-B from frame n through frame n+3 change (+, ⁇ ), (+, ⁇ ), (-, ⁇ ) and (-, ⁇ ) in this order. That is to say, these combinations of the subpixel 1-a-B have the same polarity change pattern as, but a different storage capacitor line voltage variation pattern from, those of the subpixel 1-a-A.
  • the voltage on each storage capacitor line is supposed to change periodically in regular cycles of 20H during the display period.
  • the voltage on each storage capacitor line may also change in regular cycles of 16H during the display period as shown in portion (a) of FIG. 18 .
  • the storage capacitor line voltage changes every 13H in the first and third regulation periods BH but changes every 9H in the second and fourth regulation periods BH, for example.
  • the storage capacitor line voltage may also change in regular cycles of 24H during the display period as shown in portion (b) of FIG. 18 .
  • the storage capacitor line voltage changes every 15H in the first and third regulation periods BH but changes every 21H in the second and fourth regulation periods BH, for example.
  • the intervals of the variation in storage capacitor line voltage during the BH period may be appropriately changed according to the V-total value.
  • the voltage on each storage capacitor line is supposed to complete one cycle of change during each regulation period.
  • the voltage on each storage capacitor line may also change periodically during each regulation period either in a cycle time of 2H as shown in portion (a) of FIG. 19 or in a cycle time of 1H as shown in portion (b) of FIG. 19 .
  • the voltage on each storage capacitor line may also be maintained at the average of VcH and VcL during each regulation period as shown in portion (c) of FIG. 19 .
  • each vertical scanning period has a duration of 810H and the storage capacitor voltages Vcs1 through Vcs3 change periodically in regular cycles of 20H during the display period but changes every 5H during the regulation period.
  • a half-cycle period may be provided as a regulation period for the storage capacitor line voltage and the polarity may be inverted every other vertical scanning period. Then, as already described with reference to FIG. 17 , the first change of storage capacitor voltages at the beginning of the third vertical scanning period can be different from the first change of storage capacitor voltages at the beginning of the first vertical scanning period. As a result, the brightness levels and polarities of subpixels can be changed as shown in portion (a) of FIG. 6 .
  • each regulation period is supposed to be an even number of times as long as one horizontal scanning period.
  • Each regulation period may also be an odd number of times as long as one horizontal scanning period. Even if the first and third regulation periods have a cycle time of 37H and if the second and fourth regulation periods have a cycle time of 27H as shown in FIG. 21 , the degree of non-smoothness of the image on the screen can also be reduced by inverting the brightness levels and polarities of respective subpixels as in a situation where each regulation period is an even number of times as long as one horizontal scanning period.
  • the same storage capacitor line is supposed to be connected to two subpixels belonging to two different adjacent pixels.
  • the present invention is in no way limited to that specific preferred embodiment. Two different storage capacitor lines may also be provided for two subpixels belonging to two different adjacent pixels and the voltages on those two storage capacitor lines may be changed independently of each other.
  • FIG. 22 shows the brightness levels and polarities of respective subpixels that have changed within the effective scanning period of a certain frame.
  • the liquid crystal display device 100 also has ten storage capacitor trunks CS1 through CS10.
  • the storage capacitor trunk CS1 is connected to subpixels 1-a-A, 1-b-A , 1-c-A; etc. on the first row of pixels and to subpixels 6-a-A, 6-b-A, 6-c-A, etc. on the sixth row of pixels.
  • the storage capacitor trunk CS2 is connected to subpixels 1-a-B, 1-b-B, 1-c-B, etc.
  • FIG. 23 illustrates an equivalent circuit of the liquid crystal display device 100 with the configuration shown in FIG. 22 .
  • FIG. 24 shows the waveforms of various voltages (or signals) to drive the liquid crystal display device.
  • Vsa and Vsb represent the voltages on the signal lines Sa and Sb
  • Vg1 through Vg12 represent the voltages on the scan lines G1 through G12
  • Vcs1 through Vcs10 represent the voltages on the storage capacitor trunks CS1 through CS10
  • VLsp1-a-A through VLsp2-b-B represent the effective voltages applied to the liquid crystal layers of the subpixels 1-a-A through 2-b-B, respectively.
  • What is shown in FIG. 24 is voltage waveforms within one vertical scanning period.
  • the voltages Vcs1 through Vcs10 on the storage capacitor trunks CS1 through CS10 oscillate with the same amplitude and in the same regular cycles.
  • one oscillation cycle time is 10 H.
  • the voltages Vcs1 and Vcs2 have such a relation that if one of these two voltages changes into VcH, the other voltage will change into VcL and that if one of these two voltages changes into VcL, the other voltage will change into VcH.
  • Vcs3 and Vcs4, Vcs5 and Vcs6, Vcs7 and Vcs8, and Vcs9 and Vcs10 too have the same relation as that pair of voltages Vcs1 and Vcs2.
  • the voltage Vcs1 increases ( ⁇ ) and the voltage Vcs2 decreases ( ⁇ ).
  • the voltage Vcs3 decreases ( ⁇ ) and the voltage Vcs4 increases ( ⁇ ).
  • the liquid crystal display device with the configuration shown in FIG. 22 can also reduce the viewing angle dependence of the r characteristic and minimize the deterioration of display quality.
  • a single signal line 14 is provided as a common line for two subpixels 10a and 10b included in the same pixel 10 as shown in FIG. 8 .
  • the present invention is in no way limited to that specific preferred embodiment.
  • Two different signal lines may also be provided for two subpixels included in the same pixel. In that case, even if the voltages on storage capacitor lines are not changed subpixel by subpixel, mutually different effective voltages can also be applied to the liquid crystal layers of subpixels by varying the voltages on the signal lines.
  • FIG. 25 illustrates a pixel 10, of which the two subpixels 10a and 10b are provided with signal lines 14a and 14b, respectively.
  • the pixel 10 includes two subpixel electrodes 18a and 18b that are connected to the two different signal lines 14a and 14b via their associated TFTs 16a and 16b, respectively.
  • the TFTs 16a and 16b have their gates connected to the same scan line (i.e., gate bus line) 12 in common and have their ON/OFF states controlled using the same scan signal.
  • signal voltages or grayscale voltages
  • the gates of the TFTs 16a and 16b be used in common.
  • the voltage applied to the counter electrode is shown to be constant. However, the present invention is in no way limited to that specific preferred embodiment.
  • the voltage applied to the counter electrode may be changed with time.
  • FIG. 10 shows that the effective voltages applied to the first and second subpixels are different from each other in a broad grayscale range.
  • the effective voltages applied to the subpixels could be different from each other only in a particular grayscale range (e.g., in the range of 36 th through 128 th grayscales in a 256 grayscale display in which the grayscale range from black to white is divided into 256 levels consisting of 0 th through 255 th grayscales).
  • the present invention contributes to improving the display quality of a normally black mode liquid crystal display device (e.g., an MVA mode LCD, among other things), the present invention is in no way limited to that specific preferred embodiment. If necessary, this invention is also applicable for use in an IPS mode liquid crystal display device.
  • the viewing angle dependence of the r characteristic is more significant in the MVA and ASM modes than in the IPS mode. In the IPS mode, however, it is more difficult to manufacture panels that can have a high contrast ratio in the frontal viewing direction than in the MVA and ASM modes. In view of these considerations, it can be seen that it is a more urgent task to overcome the viewing angle dependence problem of the ⁇ characteristic of the MVA and ASM mode liquid crystal display devices.
  • liquid crystal display device 100 is different from the counterpart of the first preferred embodiment described above in the brightness levels and polarities of subpixels and the order of change of the effective voltages in the four consecutive vertical scanning periods.
  • the similar description as that of the Embodiment 1 is omitted for avoiding redundancy.
  • the first, fourth and fifth periods are first polarity periods, while the second, third and sixth periods are second polarity periods. Looking at any series of four vertical scanning periods, it can be seen that two out of the four are first polarity periods and the rest is second polarity periods.
  • the first and fourth periods are first polarity periods and the second and third periods are second polarity periods.
  • the first polarity periods include a period that satisfies
  • the second polarity periods include a period that satisfies
  • Portions (b) and (c) of FIG. 26 show the effective voltages VLspa and VLspb that are applied to the respective liquid crystal layers of the first and second subpixels in the respective vertical scanning periods. The levels of these voltages are indicated by the bold lines.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels are the effective values of the differences between the voltages applied to the first and second subpixel electrodes and the voltage Vc applied to the counter electrode. In this example, the voltage Vc applied to the counter electrode is shown as being constant.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the first period is a first polarity period and the first subpixel is brighter than the second subpixel.
  • the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the second period is a second polarity period and the second subpixel is brighter than the first subpixel.
  • the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the third period is a second polarity period and the first subpixel is brighter than the second subpixel.
  • the fourth period the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the fourth period is a first polarity period and the second subpixel is brighter than the first subpixel. From the fifth period on, the brightness levels and polarities of the first and second subpixels will vary in quite the same pattern as the first and second subpixels in the first through fourth periods.
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B, +), (D, -), (B, -) and (D, +), while the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (B, -), (D, -) and (B, +) as shown in portion (a) of FIG. 26 .
  • the liquid crystal display device of this preferred embodiment inverts the brightness levels of the subpixels every vertical scanning period and also inverts their polarities every other vertical scanning period.
  • each set of first and second polarity periods has a period in which the first subpixel is brighter than the second subpixel as in the liquid crystal display device of the first preferred embodiment.
  • FIG. 27 shows the brightness levels and polarities of the first and second subpixels and the first change of voltages on the storage capacitor lines at the vertical scanning period of the first and second subpixels.
  • the four consecutive frames are identified by n, n+1, n+2 and n+3, respectively.
  • the polarity of the first and second subpixels is positive "+”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase “ ⁇ ”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the polarity of the first and second subpixels is negative "-"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase " ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the polarity of the first and second subpixels is negative “-"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease " ⁇ ”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ”.
  • the polarity of the first and second subpixels is positive "+”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease " ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ".
  • the first and second subpixels shown in portion (a) of FIG. 6 which have been referred to for the description of the first preferred embodiment, were interchanged with each other, the brightness levels and polarities of the subpixels in the second through fifth periods would correspond with those of the subpixels in the first through fourth periods shown in portion (a) of FIG. 26 . That is why if the display area of the first subpixel electrode is as large as that of the second subpixel electrode, then the liquid crystal display device of this preferred embodiment will achieve substantially the same effects as the counterpart of the first preferred embodiment described above.
  • liquid crystal display device 100 is different from the counterparts described above in the brightness levels and polarities of subpixels and the order of change of the effective voltages in the four consecutive vertical scanning periods. In the following description, the repeated description is omitted for avoiding redundancy.
  • the first, third and fifth periods are first polarity periods
  • the second, fourth and sixth periods are second polarity periods in the liquid crystal display device 100 of this preferred embodiment. Looking at any series of four vertical scanning periods, it can be seen that two out of the four are first polarity periods and the rest is second polarity periods.
  • the first and third periods are first polarity periods and the second and fourth periods are second polarity periods.
  • the first polarity periods include a period that satisfies
  • the second polarity periods include a period that satisfies
  • Portions (b) and (c) of FIG. 28 show the effective voltages VLspa and VLspb that are applied to the respective liquid crystal layers of the first and second subpixels in the respective vertical scanning periods. The levels of these voltages are indicated by the bold lines.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels are the effective values of the differences between the voltages applied to the first and second subpixel electrodes and the voltage Vc applied to the counter electrode. In this example, the voltage Vc applied to the counter electrode is shown as being constant.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the first period is a first polarity period and the first subpixel is brighter than the second subpixel.
  • the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the second period is a second polarity period and the first subpixel is brighter than the second subpixel.
  • the third period the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the third period is a first polarity period and the second subpixel is brighter than the first subpixel.
  • the fourth period the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the fourth period is a second polarity period and the second subpixel is brighter than the first subpixel. From the fifth period on, the brightness levels and polarities of the first and second subpixels will vary in quite the same pattern as the first and second subpixels in the first through fourth periods.
  • the frame frequency may be 120 Hz, for example.
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B, +), (B, -), (D, +) and (D, -), while the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (D, -), (B, +) and (B, -) as shown in portion (a) of FIG. 28 .
  • the liquid crystal display device of this preferred embodiment inverts the brightness levels of the subpixels every other vertical scanning period and also inverts their polarities every vertical scanning period.
  • since the brightness levels of the subpixels are inverted every other vertical scanning period unlike the liquid crystal display device disclosed in Patent Document No.
  • the degree of non-smoothness of the image on the screen can be reduced.
  • the brightness levels of the first and second subpixels are inverted in any of the first and second polarity periods unlike the liquid crystal display device disclosed in Patent Document No. 2.
  • the average of the effective voltages VLspa and that of the effective voltages VLspb over multiple vertical scanning periods e.g., the first through fourth periods
  • the averages of the effective voltages VLspa and VLspb can be both controlled to zero by adjusting the counter voltage. As a result, the residual image and other reliability-related problems can be overcome.
  • Vg represents the voltage on the scan line
  • Vcsa and Vcsb represent the voltages on the first and second storage capacitor lines, respectively
  • VLspa and VLspb represent the effective voltages applied to the respective liquid crystal layers of the first and second subpixels.
  • the voltages on the first and second storage capacitor lines vary in regular cycles of 20H by increasing or decreasing every 10H through the display periods AH .
  • the voltages on the first and second storage capacitor lines increase or decrease every 18H during the first and third regulation periods BH and increase or decrease every 13H during the second and fourth regulation periods BH.
  • the effective voltages applied to the respective liquid crystal layers of the first and second subpixels change as the voltages on the first and second storage capacitor lines vary.
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B, +), (B, -), (D, +) and (D, -)
  • the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (D, -), (B, +) and (B, -).
  • the brightness levels and polarities of the first and second subpixels change as shown in portion (a) of FIG. 28 . Consequently, the liquid crystal display device of this preferred embodiment can minimize the deterioration of display quality with the viewing angle dependence of the ⁇ characteristic reduced.
  • FIG. 30 shows the brightness levels and polarities of the first and second subpixels and the first change of voltages on the storage capacitor lines at the vertical scanning period of the first and second subpixels.
  • the four consecutive frames are identified by n, n+1, n+2 and n+3, respectively.
  • the polarity of the first and second subpixels is positive "+”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase " ⁇ ”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the polarity of the first and second subpixels is negative "-”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease " ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ".
  • the polarity of the first and second subpixels is positive “+”, the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease " ⁇ ", and the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ”.
  • the polarity of the first and second subpixels is negative "-"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase " ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the difference in the brightness inversion interval of the subpixels between the liquid crystal display device of this preferred embodiment and the counterpart of the first preferred embodiment will be described.
  • the brightness levels of the subpixels invert every other vertical scanning period as shown in FIG. 28 .
  • the brightness levels of the subpixels invert every vertical scanning period as shown in FIG. 6 . That is to say, the subpixel brightness inversion interval of the liquid crystal display device of this preferred embodiment is twice as long as that of the liquid crystal display device of the first preferred embodiment.
  • the non-smoothness of the image on the screen can be reduced by inverting the brightness levels of the subpixels as described above.
  • the shorter the subpixel brightness inversion interval the more significantly the non-smoothness can be reduced.
  • the orientations of the liquid crystal molecules could not change so much within one vertical scanning period that the luminance could fall short of a predetermined value. That is to say, if one vertical scanning period were too short for the response speed of liquid crystal molecules, the difference in luminance between the subpixels would not be so much as to reduce the viewing angle dependence of the ⁇ characteristic significantly.
  • Table 1 summarizes how the display qualities of the liquid crystal display devices disclosed in Patent Documents Nos. 1 and 2 and the device of the first and this preferred embodiments of the present invention were affected when the frame frequencies were changed.
  • a good display quality is indicated by the open circle ⁇ , while a poor display quality is indicated by the cross ⁇ .
  • the liquid crystal display device of Patent Document No. 1 improves the viewing angle characteristic at every frame frequency but made the viewer find the image on the screen non-smooth at any frame frequency, which is a problem. Meanwhile, as for the liquid crystal display device disclosed in Patent Document No. 2, its reliability was too questionable to manufacture it on an industrial basis.
  • the liquid crystal display devices of the first and third preferred embodiments of the present invention raised no reliability issues unlike the device of Patent Document No. 2, and therefore, can be manufactured on an industrial basis with no problem at all. Added to that, the liquid crystal display devices of the first and third preferred embodiments could also overcome the image non-smoothness problem with the device of Patent Document No. 1.
  • the liquid crystal display device of the first preferred embodiment achieved good display qualities at frame frequencies of equal to or more than 60 Hz and equal to less than 90 Hz.
  • the liquid crystal display device of this preferred embodiment could present a flicker-free image as long as the frame frequency was equal to or higher than 120 Hz.
  • the present inventors confirmed via experiments that if the frame frequency was equal to or higher than 120 Hz, the liquid crystal display device of this preferred embodiment could reduce the viewing angle dependence of the ⁇ characteristic sufficiently effectively. Once the frame frequency exceeds that value, however, it is preferred that the response speed be increased by changing the liquid crystal materials or driving methods into more appropriate ones.
  • liquid crystal display device 100 is different from the counterparts described above in the brightness levels and polarities of subpixels and the order of change of the effective voltages in the four consecutive vertical scanning periods. In the following description, the repeated description is omitted for avoiding redundancy.
  • the first, third and fifth periods are first polarity periods
  • the second, fourth and sixth periods are second polarity periods in the liquid crystal display device 100 of this preferred embodiment. Looking at any series of four vertical scanning periods, it can be seen that two out of the four are first polarity periods and the rest is second polarity periods.
  • the first and third periods are first polarity periods and the second and fourth periods are second polarity periods.
  • the first polarity periods include a period that satisfies
  • the second polarity periods include a period that satisfies
  • Portions (b) and (c) of FIG. 31 show the effective voltages VLspa and VLspb that are applied to the respective liquid crystal layers of the first and second subpixels in the respective vertical scanning periods. The levels of these voltages are indicated by the bold lines.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels are the effective values of the differences between the voltages , applied to the first and second subpixel electrodes and the voltage Vc applied to the counter electrode. In this example, the voltage Vc applied to the counter electrode is shown as being constant.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the first period is a first polarity period and the first subpixel is brighter than the second subpixel.
  • the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the second period is a second polarity period and the second subpixel is brighter than the first subpixel.
  • the third period the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the third period is a first polarity period and the second subpixel is brighter than the first subpixel.
  • the fourth period the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the fourth period is a second polarity period and the first subpixel is brighter than the second subpixel. From the fifth period on, the brightness levels and polarities of the first and second subpixels will vary in quite the same pattern as the first and second subpixels in the first through fourth periods.
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B, +), (D, -), (D, +) and (B, -), while the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (B, -), (B, +) and (D, -) as shown in portion (a) of FIG. 31 .
  • the liquid crystal display device of this preferred embodiment inverts the brightness levels of the subpixels every other vertical scanning period and also inverts their polarities every vertical scanning period.
  • the frame frequency may be 120 Hz, for example.
  • FIG. 32 shows the brightness levels and polarities of the first and second subpixels and the first change of voltages on the storage capacitor lines at the vertical scanning period of the first and second subpixels.
  • the four consecutive frames are identified by n, n+1, n+2 and n+3, respectively.
  • the polarity of the first and second subpixels is positive “+”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase “ ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the polarity of the first and second subpixels is negative "-"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase " ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the polarity of the first and second subpixels is positive “+”, the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease “ ⁇ ", and the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ”.
  • the polarity of the first and second subpixels is negative “-”, the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease " ⁇ ", and the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ".
  • the degree of non-smoothness of the image on the screen can be reduced.
  • the average of the effective voltages VLspa and that of the effective voltages VLspb over multiple vertical scanning periods e.g., the first through fourth periods
  • the averages of the effective voltages VLspa and VLspb can be both controlled to zero by adjusting the counter voltage.
  • the brightness levels and polarities of the subpixels 1-a-A and 1-a-B change as in the first through fourth periods shown in portion (a) of FIG. 31 when the liquid crystal display device of the third preferred embodiment is subjected to the dot inversion drive as already described with reference to FIGS. 14 and 15 , then the brightness levels .and polarities of the subpixels 2-a-A and 2-a-B will change as in the second through fifth periods shown in portion (a) of FIG. 28 .
  • liquid crystal display device 100 of this preferred embodiment is different from the counterparts described above in the brightness levels and polarities of subpixels and the order of change of the effective voltages in the four consecutive vertical scanning periods. In the following description, the repeated description is omitted for avoiding redundancy.
  • the first, fourth and fifth periods are first polarity periods
  • the second, third and sixth periods are second polarity periods in the liquid crystal display device 100 of this preferred embodiment.
  • two out of the four are first polarity periods and the rest is second polarity periods.
  • the first and fourth periods are first polarity periods and the second and third periods are second polarity periods.
  • the first polarity periods include a period that satisfies
  • the second polarity periods include a period that satisfies
  • Portions (b) and (c) of FIG. 33 show the effective voltages VLspa and VLspb that are applied to the respective liquid crystal layers of the first and second subpixels in the respective vertical scanning periods. The levels of these voltages are indicated by the bold lines.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels are the effective values of the differences between the voltages applied to the first and second subpixel electrodes and the voltage Vc applied to the counter electrode. In this example, the voltage Vc applied to the counter electrode is shown as being constant.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the first period is a first polarity period and the first subpixel is brighter than the second subpixel.
  • the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the second period is a second polarity period and the first subpixel is brighter than the second subpixel.
  • the third period the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the third period is a second polarity period and the second subpixel is brighter than the first subpixel.
  • the fourth period the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the fourth period is a first polarity period and the second subpixel is brighter than the first subpixel. From the fifth period on, the brightness levels and polarities of the first and second subpixels will vary in quite the same pattern as the first and second subpixels in the first through fourth periods.
  • the frame frequency may be 120 Hz, for example.
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B, +), (B, -), (D, -) and (D, +), while the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (D, -), (B, -) and (B, +) as shown in portion (a) of FIG. 33 .
  • the liquid crystal display device of this preferred embodiment inverts the brightness levels of the subpixels every other vertical scanning period and also inverts their polarities every other vertical scanning period. But the timing of inversion of the polarities is shifted by one vertical scanning period from that of the brightness levels of the subpixels.
  • the degree of non-smoothness of the image on the screen can be reduced.
  • the brightness levels of the first and second subpixels are inverted in any of the first and second polarity periods unlike the liquid crystal display device disclosed in Patent Document No. 2.
  • the average of the effective voltages VLspa and that of the effective voltages VLspb over multiple vertical scanning periods e.g., the first through fourth periods
  • the averages of the effective voltages VLspa and VLspb can be both controlled to zero by adjusting the counter voltage. As a result, the residual image and other reliability-related problems can be overcome.
  • Vg represents the voltage on the scan line
  • Vcsa and Vcsb represent the voltages on the first and second storage capacitor lines, respectively
  • VLspa and VLspb represent the effective voltages applied to the respective liquid crystal layers of the first and second subpixels.
  • the voltages on the first and second storage capacitor lines vary in regular cycles of 20H by increasing or decreasing every 10H through the display periods AH.
  • the voltages on the first and second storage capacitor lines increase or decrease every 18H during the first through fourth regulation periods BH.
  • FIG. 35 shows the brightness levels and polarities of the first and second subpixels and the first change of voltages on the storage capacitor lines at the vertical scanning period of the first and second subpixels.
  • the four consecutive frames are identified by n, n+1, n+2 and n+3, respectively.
  • the polarity of the first and second subpixels is positive “+”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase “ ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the polarity of the first and second subpixels is negative "-”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease " ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ".
  • the polarity of the first and second subpixels is negative “-"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase “ ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the polarity of the first and second subpixels is positive “+”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease " ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ".
  • the effective voltages applied to the respective liquid crystal layers of the first and second subpixels change as the voltages on the first and second storage capacitor lines vary.
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B, +), (B, -), (D, -) and (D, +)
  • the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (D, -), (B, -) and (B, +). Consequently, the liquid crystal display device of this preferred embodiment can minimize the deterioration of display quality with the viewing angle dependence of the ⁇ characteristic reduced.
  • liquid crystal display device 100 of this preferred embodiment is different from the counterparts described above in the brightness levels and polarities of subpixels and the order of change of the effective voltages in the four consecutive vertical scanning periods. In the following description, the repeated description is omitted for avoiding redundancy.
  • the first, second, fifth and sixth periods are first polarity periods, while the third and fourth periods are second polarity periods in the liquid crystal display device 100 of this preferred embodiment. Looking at any series of four vertical scanning periods, it can be seen that two out of the four are first polarity periods and the rest is second polarity periods. For example, in the first through fourth periods shown in portion (a) of FIG. 36 , the first and second periods are first polarity periods and the third and fourth periods are second polarity periods.
  • the first polarity periods include a period that satisfies
  • the second polarity periods include a period that satisfies
  • Portions (b) and (c) of FIG. 36 show the effective voltages VLspa and VLspb that are applied to the respective liquid crystal layers of the first and second subpixels in the respective vertical scanning periods. The levels of these voltages are indicated by the bold lines.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels are the effective values of the differences between the voltages applied to the first and second subpixel electrodes and the voltage Vc applied to the counter electrode. In this example, the voltage Vc applied to the counter electrode is shown as being constant.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the first period is a first polarity period and the first subpixel is brighter than the second subpixel.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the second period is a first polarity period and the second subpixel is brighter than the first subpixel.
  • the third period the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is smaller than that of the effective voltage applied to that of the second subpixel (
  • the third period is a second polarity period and the second subpixel is brighter than the first subpixel.
  • the fourth period the voltages applied to the first and second subpixel electrodes are lower than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the fourth period is a second polarity period and the first subpixel is brighter than the second subpixel. From the fifth period on, the brightness levels and polarities of the first and second subpixels will vary in quite the same pattern as the first and second subpixels in the first through fourth periods.
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B, +), (D, +), (D, -) and (B, -), while the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (B, +), (B, -) and (D, -) as shown in portion (a) of FIG. 36 .
  • the liquid crystal display device of this preferred embodiment inverts the brightness levels of the subpixels every other vertical scanning period and also inverts their polarities every other vertical scanning period. But the timing of inversion of the polarities is shifted by one vertical scanning period from that of the brightness levels of the subpixels.
  • the degree of non-smoothness of the image on the screen can be reduced.
  • the brightness levels of the first and second subpixels are inverted in any of the first and second polarity periods as in the liquid crystal display device of the fifth preferred embodiment.
  • FIG. 37 shows the brightness levels and polarities of the first and second subpixels and the first change of voltages on the storage capacitor lines at the vertical scanning period of the first and second subpixels.
  • the four consecutive frames are identified by n, n+1, n+2 and n+3, respectively.
  • the polarity of the first and second subpixels is positive "+”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase “ ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the polarity of the first and second subpixels is positive "+”
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease " ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ".
  • the polarity of the first and second subpixels is negative "-"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is increase “ ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is decrease " ⁇ ".
  • the polarity of the first and second subpixels is negative "-"
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the first subpixel is decrease " ⁇ "
  • the first change of voltages on the storage capacitor line at the vertical scanning period of the second subpixel is increase " ⁇ ".
  • the brightness levels and polarities of the subpixels in the second through fifth periods would correspond with those of the subpixels in the first through fourth periods shown in portion (a) of FIG. 33 , which has been referred to for the description of the fifth preferred embodiment. That is why if the display area of the first subpixel electrode is as large as that of the second subpixel electrode, then the liquid crystal display device of this preferred embodiment will achieve substantially the same effects as the counterpart of the fifth preferred embodiment described above.
  • the brightness levels and polarities of the subpixels 1-a-A and 1-a-B change as in the first through fourth periods shown in portion (a) of FIG. 36 when the liquid crystal display device of this sixth preferred embodiment is subjected to the dot inversion drive as already described with reference to FIGS. 14 and 15 , then the brightness levels and polarities of the subpixels 2-a-A and 2-a-B will change as in the second through fifth periods shown in portion (a) of FIG. 33 .
  • liquid crystal display device 100 of this preferred embodiment is different from the counterparts of the first through sixth preferred embodiments described above in the subpixels change their luminances by way of a moderate luminance.
  • the repeated description is omitted for avoiding redundancy.
  • the first, third, and fifth periods are first polarity periods
  • the second, fourth and sixth periods are second polarity periods in the liquid crystal display device 100 of this preferred embodiment.
  • two out of the four are first polarity periods and the rest is second polarity periods.
  • the first and third periods are first polarity periods and the second and fourth periods are second polarity periods.
  • the first polarity periods include a period that satisfies
  • VLspa VLspb (e.g., the second and fourth periods in this example).
  • Portions (b) and (c) of FIG. 38 show the effective voltages VLspa and VLspb that are applied to the respective liquid crystal layers of the first and second subpixels in the respective vertical scanning periods. The levels of these voltages are indicated by the bold lines.
  • the effective voltages VLspa and VLspb applied to the respective liquid crystal layers of the first and second subpixels are the effective values of the differences between the voltages applied to the first and second subpixel electrodes and the voltage Vc applied to the counter electrode. In this example, the voltage Vc applied to the counter electrode is shown as being constant.
  • the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the first subpixel is greater than that of the effective voltage applied to that of the second subpixel (
  • the first period is a first polarity period and the first subpixel is brighter than the second subpixel.
  • the third period the voltages applied to the first and second subpixel electrodes are higher than the voltage applied to the counter electrode, and the absolute value of the effective voltage applied to the liquid crystal layer of the second subpixel is greater than that of the effective voltage applied to that of the first subpixel (
  • the third period is a first polarity period and the second subpixel is brighter than the first subpixel.
  • the (brightness, polarity) combination of the first subpixel changes in the order of (B, +), (M(oderate), - ), (D, +) and (M, -), while the (brightness, polarity) combination of the second subpixel changes in the order of (D, +), (M, -), (B, +) and (M, -) as shown in portion (a) of FIG. 38 , where "M" means that the brightness (or luminance) of the first subpixel is equal to that of the second subpixel.
  • the liquid crystal display device of this preferred embodiment changes the luminances of the subpixels in three steps by way of a moderate luminance every vertical scanning period and also inverts the polarities every vertical scanning period.
  • the degree of non-smoothness of the image on the screen can be reduced.
  • the average of the effective voltages VLspa and that of the effective voltages VLspb over multiple vertical scanning periods e.g., the first through fourth periods
  • the averages of the effective voltages VLspa and VLspb can be both controlled to zero by adjusting the counter voltage.
  • FIGS. 39A , 39B and 40 how the effective voltages applied to the respective liquid crystal layers of subpixels vary in the liquid crystal display device of this preferred embodiment.
  • a series of four frames (corresponding to four vertical scanning periods) will be identified herein by n, n+1, n+2 and n+3, respectively.
  • FIG. 39A illustrates the brightness levels and polarities of respective subpixels that have changed in frame n
  • FIG. 39B illustrates the brightness levels and polarities of respective subpixels that have changed in frame n+1.
  • the liquid crystal display device of this preferred embodiment has a pixel arrangement such as the one shown in FIGS. 39A and 39B , which is the same as the one that has been described for the liquid crystal display device of the first preferred embodiment with reference to FIG. 14 . Thus, the repeated description is omitted in order to avoid complicating the description excessively.
  • the liquid crystal display device of this preferred embodiment includes twelve storage capacitor trunks. In FIGS. 39A and 39B , the storage capacitor lines that are connected to the twelve storage capacitor trunks are identified herein by CS1, CS2, CS3, ... and CS12, respectively.
  • pixels 1-a, 1-b, 2-a and 2-b change.
  • the pixels 1-a and 2-b have the first polarity (+), while the pixels 1-b and 2-a have the second polarity (-) as shown in FIG. 39A .
  • each of the subpixels 1-a-A, 1-b-B, 2-a-A and 2-b-A is brighter than the other subpixel of the pixel.
  • the luminances of the respective subpixels change into a moderate one and the polarities of the respective subpixels are inverted compared to the ones during the frame n as shown in FIG. 39B .
  • the polarities of the respective subpixels are inverted compared to the ones during the frame n+1 to be the same as the ones shown in FIG. 39A , while the brightness levels of the respective subpixels are inverted compared to the ones shown in FIG. 39A .
  • the luminances of the respective subpixels change into a moderate one and the polarities of the respective subpixels are inverted to be the same as the ones shown in FIG. 39B .
  • the liquid crystal display device of this preferred embodiment regulates the voltages on the respective signal lines and the voltage applied to the counter electrode appropriately, thereby equalizing the effective voltages applied to the liquid crystal layer in respective electric field directions as closely as possible and satisfying the first condition.
  • pixels with mutually different polarities are arranged adjacent to each other as shown in FIGS. 39A and 39B , thereby satisfying the second condition as well.
  • subpixels each of which is brighter than the other subpixel of the same pixel, are arranged as randomly as possible, e.g., such that the "B" and "D” signs are arranged on a subpixel-by-subpixel basis in a checkered pattern as shown in FIG. 39A , thereby satisfying the third condition, too.
  • Table 2 summarizes how the display qualities of the liquid crystal display devices of the first, third and the present preferred embodiments were affected when the frame frequencies were changed.
  • a good display quality is indicated by the open circle ⁇ , while a poor display quality is indicated by the cross ⁇ .
  • the liquid crystal display device of this preferred embodiment achieved good display qualities at frame frequencies of 90 Hz or more.
  • Vsa and Vsb represent the voltages on the signal lines Sa and Sb
  • Vcs1 and Vcs2 represent the voltages on the first and second storage capacitor trunks CS1 and CS2
  • Vg1 represents the voltages on the scan line G1
  • VLsp1-a-A and VLsp1-b-B represent the effective voltages applied to the liquid crystal layer of the subpixels 1-a-A and 1-a-B, respectively.
  • FIG. 40 shows the waveforms of the respective voltages in the four frames of n through n+3.
  • the subpixels 1-a-A and 1-a-B have their polarities inverted in the order of (+, - , +, -) while having their luminances changed in the patterns (B, M, D, M) and (D, M, B, M), respectively.
  • the write operation is started when the voltage Vg1 on the scan line G1 goes VgH (high level).
  • One vertical scanning period V-Total of the input video signal has a duration of 801H.
  • the voltage Vcs1 on the first storage capacitor trunk CS1 has such a waveform that completes one cycle of its level change in the order of the first, second, third and second levels VL1, VL2, VL3 and VL2 every 6H period. And the voltages Vcs1 and Vcs2 have phases that are different from each other by 180 degrees.
  • the interval between the point in time when the voltage Vg1 on the scan line G1 goes VgL (i.e., low level) and the point in time when the voltages Vcs1 and Vcs2 on the storage capacitor lines change for the first time is 3H.
  • the display period of the voltage Vcs1 on the first storage capacitor trunk CS1 i.e., the first waveform period
  • each period in which its amplitude continues to be constant at the first, second or third level has a length of 6H. That is why 3H is a half of the period in which the voltage Vcs on the storage capacitor line has constant amplitude (i.e., a quarter of one cycle of each display period).
  • the voltage Vsa on the signal line Sa is higher than the voltage at the counter electrode.
  • the voltage Vsa on the signal line Sa is lower than the voltage at the counter electrode.
  • the scan line G1 is selected (i.e., the voltage Vg on the scan line goes VgH).
  • the scan line G1 voltages higher than the one at the counter electrode are applied to the subpixel electrodes of the subpixels 1-a-A and 1-a-B.
  • the voltage Vcs1 on the first storage capacitor trunk will vary periodically.
  • the voltage Vg1 on the scan line G1 goes down from VgH to VgL again, the voltage Vcs1 on the first storage capacitor trunk is VL1, while the voltage Vcs2 on the second storage capacitor trunk is VL3. Since the average voltage VL2 of the voltages Vcs1 and Vcs2 on the first and second storage capacitor trunks is higher than VL1 but lower than VL3, the absolute value of the effective voltage applied to the liquid crystal layer of the subpixel 1-a-A becomes greater than that of the effective voltage applied to that of the subpixel 1-a-B. As a result, the subpixel 1-a-A looks brighter than the subpixel 1-a-B.
  • the scan line G1 is selected (i.e., the voltage Vg on the scan line goes VgH).
  • the scan line G1 voltages lower than the one at the counter electrode are applied to the subpixel electrodes of the subpixels 1-a-A and 1-a-B.
  • the voltage Vcs1 on the first storage capacitor trunk will vary periodically.
  • the voltages Vcs1 and Vcs2 on the first and second storage capacitor trunks are equal to the average voltage VL2 of the voltages Vcs1 and Vcs2 on the first and second storage capacitor trunks. That is why the absolute value of the effective voltage applied to the liquid crystal layer of the subpixel 1-a-A becomes equal to that of the effective voltage applied to that of the subpixel 1-a-B. As a result, the subpixel 1-a-A looks as bright as the subpixel 1-a-B.
  • the scan line G1 is selected (i.e., the voltage Vg on the scan line goes VgH).
  • the scan line G1 voltages higher than the one at the counter electrode are applied to the subpixel electrodes of the subpixels 1-a-A and 1-a-B.
  • the voltage Vcs1 on the first storage capacitor trunk is VL3
  • the voltage Vcs2 on the second storage capacitor trunk is VL1.
  • the absolute value of the effective voltage applied to the liquid crystal layer of the subpixel 1-a-A becomes smaller than that of the effective voltage applied to that of the subpixel 1-a-B.
  • the subpixel 1-a-A looks darker than the subpixel 1-a-B.
  • the scan line G1 is selected (i.e., the voltage Vg on the scan line goes VgH).
  • the scan line G1 voltages lower than the one at the counter electrode are applied to the subpixel electrodes of the subpixels 1-a-A and 1-a-B.
  • the voltages Vcs1 and Vcs2 on the first and second storage capacitor trunks are equal to VL2.
  • the absolute value of the effective voltage applied to the liquid crystal layer of the subpixel 1-a-A becomes equal to that of the effective voltage applied to that of the subpixel 1-a-B.
  • the subpixel 1-a-A looks as bright as the subpixel 1-a-B.
  • the (brightness, polarity) combination of the subpixel 1-a-A changes in the order of (B, +), (M, -), (D, +) and (M, -), while the (brightness, polarity) combination of the subpixel 1-a-B changes in the order of (D, +), (M, -), (B, +) and (M, -).
  • the (brightness, polarity) combination of the subpixel 2-a-A changes in the order of (B, -), (M, +), (D, -) and (M, +).
  • the liquid crystal display device of this preferred embodiment not only changes the brightness levels of each subpixel in the order of bright, moderate, dark and moderate every vertical scanning period but also inverts the polarity every vertical scanning period, thereby reducing the degree of non-smoothness of the image on the screen.
  • each set of first and second polarity periods has a period in which the first subpixel is brighter than the second subpixel as in the liquid crystal display device of the first preferred embodiment.
  • the average of the effective voltages VLspa and that of the effective voltages VLspb over multiple vertical scanning periods can be equal to each other. Furthermore, the averages of the effective voltages VLspa and VLspb can be both controlled to zero by adjusting the counter voltage. As a result, the residual image and other reliability-related problems can be overcome.
  • each pixel is supposed to consist of two subpixels.
  • the present invention is in no way limited to those specific preferred embodiments.
  • Each pixel may also consist of three or more subpixels.
  • the greater the number of subpixels per pixel the more significantly the non-uniformity in ⁇ characteristic can be reduced. For example, if the pixel division number is increased from two to four, the degree of the non-uniformity produced by a variation in display grayscale can be reduced and the display qualities can be further improved.
  • the greater the division number the lower the (frontal) transmittance will be in the case of white display.
  • the division number needs to be appropriately adjusted according to the intended application of the liquid crystal display device so as to strike an adequate balance between the degree of reduction in the viewing angle dependence of the ⁇ characteristic and the magnitude of decrease in the transmittance in the white display.
  • the reduction in the viewing angle dependence of the ⁇ characteristic is most noticeable if a non-divided pixel is divided into two subpixels (i.e., when each pixel consists of two subpixels).
  • each pixel preferably consists of two subpixels, after all.
  • each voltage Vcs will have an increased number of waveform options in the display period and the regulation period, which is beneficial. Nevertheless, the voltage Vcs should change its levels at least once after the voltage on the scan line has gone low during one vertical scanning period.
  • a liquid crystal display device that includes twice as many storage capacitor lines as scan lines and that has a configuration for supplying voltages Vcs to those storage capacitor lines independently of each other, if the voltage Vcs needs to change its levels only once after the voltage on each scan line has gone low, then the interval between the point in time when the voltage on the scan line goes low and the point in time when the voltage Vcs changes its levels or the interval between the point in time when the voltage Vcs changes its levels and the point in time when the voltage on the scan line goes high next time is preferably defined equally for every display line.
  • the voltages Vcs on those multiple storage capacitor lines connected to a single storage capacitor trunk can have their oscillation amplitudes exactly matched with each other, which is advantageous.
  • the circuit configuration can also be simpler than a situation where a lot of voltages should be supplied independently of each other.
  • the liquid crystal display device according to any of the first through seventh preferred embodiments of the present invention described above is supposed to adopt the multi-picture element driving method disclosed in Patent Document No. 1, i.e., make the luminances of two subpixels that form one pixel different from each other by applying a rectangular wave voltage to a CS bus line.
  • the present invention is in no way limited to those specific preferred embodiments.
  • the present invention has the following two important points, and embodiments embodied these points are in no way limited to the above described embodiments.
  • the first point of the present invention is to switch the luminance levels of multiple subpixels that form a single pixel one after another, thereby averaging the luminance levels of those subpixels over a predetermined period of time and optimizing the variation in the luminance level of each subpixel with time such that the difference in luminance level between the subpixels becomes substantially equal to zero.
  • the second point of the present invention is to invert the polarities of respective subpixels such that the averages of the voltages applied to those subpixels over a certain period of time becomes substantially equal to each other among them, thereby optimizing the variation in the effective voltage applied to the liquid crystal layer (or the variation in luminance). It should be noted that to ensure reliability, the difference in average effective voltage between the subpixels is preferably 1 V or less.
  • liquid crystal display devices that embody these two important points include a device in which subpixels that form each pixel have the same number of sets of four frames with the pixel polarity-subpixel brightness combinations (B, +), (B, -), (D, +) and (D, -) (where B and D stand for "bright” and “dark", respectively) within a certain period and another device in which subpixels that form each pixel have the same number of sets of four frames with the pixel polarity-subpixel brightness combinations (B, +), (D, +), (M, -) and (M, -) or (B, -), (D, -), (M, -) and (M, -) (where M stands for "moderate”) within a certain period.
  • the polarities and luminances of subpixels may be controlled on a frame-by-frame basis unlike the liquid crystal display device according to any of the first through seventh preferred embodiments of the present invention described above.
  • a TFT provided for each subpixel may drive it with data signals and scan signals applied independently to respective subpixels.
  • the liquid crystal display device may also be designed such that a TFT provided for each subpixel controls the luminance with a data signal that has been applied independently on a subpixel-by-subpixel basis but that those TFTs are driven through a common scan line as shown in FIG. 25 .
  • the luminances and polarities of respective subpixels can be controlled with independent data signals applied to those subpixels.
  • the liquid crystal display device may also be designed such that a TFT provided for each subpixel controls its luminance with a data signal applied in common for respective subpixels but that the TFTs are driven through respectively different scan lines.
  • a TFT provided for each subpixel controls its luminance with a data signal applied in common for respective subpixels but that the TFTs are driven through respectively different scan lines.
  • the luminances and polarities of the respective subpixels can be controlled.
  • the present invention provides a big-screen or high-definition liquid crystal display device that realizes very high display qualities with the viewing angle dependence of the ⁇ characteristic reduced significantly.
  • the liquid crystal display device of the present invention can be used effectively as a TV monitor of a big screen size of 30 inches or more. Further embodiments are:

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EP10015233A 2006-08-24 2007-08-13 Flüssigkristallanzeigeanordnung Withdrawn EP2284829A1 (de)

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WO2011024966A1 (ja) * 2009-08-28 2011-03-03 シャープ株式会社 液晶表示装置
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EP2056286B1 (de) 2014-07-16
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EP2056286A1 (de) 2009-05-06
WO2008023601A1 (fr) 2008-02-28
EP2284828A1 (de) 2011-02-16
CN101506866A (zh) 2009-08-12
JPWO2008023601A1 (ja) 2010-01-07
CN101506866B (zh) 2013-08-21

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