Patent Application
20120299898
The present invention relates to a liquid crystal display device.
Liquid crystal display devices are currently used in a variety of applications. In a general liquid crystal display device, one picture element consists of three pixels respectively representing red, green and blue, which are the three primary colors of light, thereby conducting a display operation in colors.
A known liquid crystal display device, however, can reproduce colors that fall within only a narrow range (which is usually called a “color reproduction range”), which is a problem. If the color reproduction range is narrow, then some of the object colors (i.e., the colors of various objects existing in Nature, see Non-Patent Document No. 1) cannot be represented. Thus, to broaden the color reproduction range of liquid crystal display devices, a technique for increasing the number of primary colors for use to perform a display operation has recently been proposed.
For example, Patent Document No. 1 discloses a liquid crystal display device 800 in which one picture element P is made up of four pixels that include not only red, green and blue pixels R, G and B representing the colors red, green and blue, respectively, but also a yellow pixel Y representing the color yellow as shown in
By increasing the number of primary colors for use to conduct a display operation (i.e., by performing a display operation using four or more primary colors), the color reproduction range can be broadened compared to a known liquid crystal display device that uses only the three primary colors for display purposes. Such a liquid crystal display device that conducts a display operation using four or more primary colors will be referred to herein as a “multi-primary-color liquid crystal display device”. And a liquid crystal display device that conducts a display operation using the three primary colors will be referred to herein as a “three-primary-color liquid crystal display device”.
However, if the number of primary colors for use to conduct a display operation is increased, then the number of pixels per picture element increases, and therefore, the area given to each of those pixels should decrease. Consequently, the lightness of the color represented by each pixel should decrease. For example, if the number of primary colors for use to conduct a display operation is increased from three to four, the area given to each pixel decreases to three-quarters, and the lightness of each pixel drops to three-quarters, too. Also, if the number of primary colors for use to conduct a display operation is increased from three to six, the area given to each pixel decreases to one half, and the lightness of each pixel drops to one half, too.
As for a pixel representing the color green or blue, even if its lightness decreases, the pixel can still represent various object colors well enough. As for a pixel representing the color red, however, if its lightness decreases, the pixel can no longer represent some of those object colors. In this manner, if the lightness decreases due to an increase in the number of primary colors to use, the display quality of the color red will be debased and the color red will turn into a blackish red (i.e., a dark red).
A technique for overcoming such a problem is proposed in Patent Document No. 2.
However, if such pixels with the larger area (which will be referred to herein as “larger pixels”) and pixels with the smaller area (which will be referred to herein as “smaller pixels”) are included in the same mix as in the liquid crystal display device 900 of Patent Document No. 2, then the effective value of the voltage applied to its liquid crystal layer to conduct a display operation in a single color will be different between the larger and smaller pixels.
The reason will be described below. If a display signal (source signal) supplied to a signal line changes after a pixel has been charged, a potential at a pixel electrode (drain voltage) also varies due to the presence of a parasitic capacitance (source-drain capacitance) Csd between the source and the drain as shown in
ΔV=Vspp·(Csd/Cpix) (1)
where Vspp is the magnitude of variation (i.e., the amplitude) of the source signal, Csd is the source-drain capacitance Csd, and Cpix is the pixel capacitance.
The larger and smaller pixels have substantially the same source-drain capacitance Csd but significantly different pixel capacitances Cpix. Thus, as can be seen from Equation (1), even if the larger and smaller pixels cause the same magnitude of variation Vspp of the source signal, those pixels will cause different magnitudes of variation ΔV of the drain voltage. Consequently, the effective value of the voltage applied to the liquid crystal layer becomes significantly different between the larger and smaller pixels, thus debasing the display quality.
In order to overcome such problems, the present invention has been made to provide a liquid crystal display device that can easily adjust the source-drain capacitance Csd on a pixel-by-pixel basis.
A liquid crystal display device according to the present invention has a plurality of pixels which are arranged in columns and rows to form a matrix pattern. The device includes: an active-matrix substrate that includes pixel electrodes that are provided for the respective pixels, a plurality of scan lines that run in a row direction, and a plurality of signal lines that run in a column direction; a counter substrate that faces the active-matrix substrate; and a liquid crystal layer that is interposed between the active-matrix substrate and the counter substrate. Each of the plurality of signal lines includes, in an area given to each of multiple pixel rows that are defined by those pixels, a first straight portion that overlaps with only one of two pixel electrodes that are adjacent to the signal line, a second straight portion that overlaps with only the other pixel electrode, and a bent portion that connects the first and second straight portions together. The respective bent portions of two arbitrary ones of the signal lines, which are adjacent to each other in the row direction, are arranged at mutually different positions in the column direction.
In one preferred embodiment, in at least some of the signal lines, the first and second straight portions have mutually different widths.
Another liquid crystal display device according to the present invention has a plurality of pixels which are arranged in columns and rows to form a matrix pattern. The device includes: an active-matrix substrate that includes pixel electrodes that are provided for the respective pixels, a plurality of scan lines that run in a row direction, and a plurality of signal lines that run in a column direction; a counter substrate that faces the active-matrix substrate; and a liquid crystal layer that is interposed between the active-matrix substrate and the counter substrate. Each of the plurality of signal lines includes, in an area given to each of multiple pixel rows that are defined by those pixels, a first straight portion that overlaps with only one of two pixel electrodes that are adjacent to the signal line, a second straight portion that overlaps with only the other pixel electrode, and a bent portion that connects the first and second straight portions together. In at least some of the signal lines, the first and second straight portions have mutually different widths.
In one preferred embodiment, each of the multiple pixel rows includes a larger pixel that has a relatively large area and a smaller pixel that has a relatively small area.
In one preferred embodiment, the area of overlap between the pixel electrode of the larger pixel and a signal line that supplies a grayscale voltage to the pixel electrode of that larger pixel is greater than the area of overlap between the pixel electrode of the smaller pixel and a signal line that supplies a grayscale voltage to the pixel electrode of that smaller pixel.
In one preferred embodiment, the Csd/Cpix ratio of the source-drain capacitance Csd of the larger pixel to a pixel capacitance Cpix is substantially equal to the Csd/Cpix ratio of the source-drain capacitance Csd of the smaller pixel to the pixel capacitance Cpix.
In one preferred embodiment, the larger and smaller pixels are arranged alternately in the row direction.
In one preferred embodiment, the area of overlap between one of two signal lines that are adjacent to the larger pixel and the pixel electrode of that larger pixel is substantially equal to the area of overlap between the other signal line and the pixel electrode of that larger pixel. And the area of overlap between one of two signal lines that are adjacent to the smaller pixel and the pixel electrode of that smaller pixel is substantially equal to the area of overlap between the other signal line and the pixel electrode of that smaller pixel.
In one preferred embodiment, the plurality of pixels includes red, green and blue pixels that represent the colors red, green and blue, respectively.
In one preferred embodiment, the plurality of pixels further includes a yellow pixel that represents the color yellow.
In one preferred embodiment, the red pixel is the larger pixel.
In one preferred embodiment, the blue pixel is the larger pixel and the green and yellow pixels are the smaller pixels.
In one preferred embodiment, each of the plurality of pixels includes a plurality of subpixels, mutually different voltages being applicable to the respective liquid crystal layers of the subpixels.
In one preferred embodiment, the plurality of subpixels are arranged in the column direction, and the bent portion is arranged at a position that has been set for a particular one of the subpixels and each of the plurality of signal lines has a further bent portion that is arranged at a position that has been set for a different subpixel from that particular subpixel.
In one preferred embodiment, the respective further bent portions of two arbitrary ones of the signal lines, which are adjacent to each other in the row direction, are arranged at mutually different positions in the column direction.
The present invention provides a liquid crystal display device that can easily adjust the source-drain capacitance Csd on a pixel-by-pixel basis. According to the present invention, for example, in a liquid crystal display device in which multiple different kinds of pixels with mutually different areas are included in the same mix, the variation in the effective voltage applied to the liquid crystal layer can be reduced.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention is in no way limited to the specific embodiments to be described below.
As shown in
Hereinafter, the structure of this liquid crystal display device 100 will be described in further detail with reference to
The liquid crystal display device 100 includes an active-matrix substrate 10, a counter substrate 20 that faces the active-matrix substrate 10, and a liquid crystal layer 30 that is interposed between the active-matrix substrate 10 and the counter substrate 20.
The active-matrix substrate 10 includes pixel electrodes 11, each of which is provided for an associated one of the pixels, a plurality of scan lines 12 that run in the row direction, and a plurality of signal lines 13 that run in the column direction. The pixel electrodes 11 are connected to thin-film transistors (TFTs) 14. Each TFT is supplied with not only a scan signal from its associated scan line 12 but also a display signal from its associated signal line 13.
The scan lines 12 are arranged on a transparent substrate (e.g., a glass substrate) 10a with electrically insulating properties. On the transparent substrate 10a, also arranged is a storage capacitor line 15 that runs in the row direction. The storage capacitor line 15 and the scan lines 12 are made of the same conductor film. A portion 15a of the storage capacitor line 15 that is located near the center of each pixel has a broader width than the rest of the line 15 and functions as a storage capacitor counter electrode. The storage capacitor counter electrode 15a is supplied with a storage capacitor counter voltage (CS voltage) from the storage capacitor line 15.
A gate insulating film 16 is arranged to cover the scan lines 12 and the storage capacitor lines 15. On the gate insulating film 16, arranged are not only the signal lines 13 but also storage capacitor electrodes 17, which are made of the same conductor film as the signal lines 13. Also, each of the storage capacitor electrodes 17 is electrically connected to the drain electrode of its associated TFT 14 and is supplied with the same voltage as its associated pixel electrode 11 via the TFT 14.
An interlayer insulating film 18 is arranged to cover the signal lines 13 and the storage capacitor electrodes 17. The pixel electrodes 11 are located on the interlayer insulating film 18. The pixel electrodes 11 are arranged so that their edges overlap with the scan lines 12 and the signal lines 13 with the interlayer insulating film 18 interposed between them.
An alignment film 19 is arranged on the uppermost surface (i.e., the surface that is closest to the liquid crystal layer 30) of the active-matrix substrate 10. Depending on the display mode, the alignment film 19 may be a horizontal alignment film or a vertical alignment film.
The counter substrate 20 includes a counter electrode 21, which faces the pixel electrodes 11 and which is arranged on a transparent substrate (such as a glass substrate) 20a with electrically insulating properties. An alignment film 29 is arranged on the uppermost surface (i.e., the surface that is closest to the liquid crystal layer 30) of the counter substrate 20. Depending on the display mode, the alignment film 29 may be a horizontal alignment film or a vertical alignment film.
Although not shown in any of the drawings, the counter substrate 20 typically further includes a color filter layer and an opaque layer (i.e., a black matrix). The color filter layer includes red, green, blue, and yellow color filters that transmit red, green, blue, and yellow rays, respectively, and that are associated with the red, green, blue, and yellow pixels R, G, B and Y, respectively.
The liquid crystal layer 30 includes liquid crystal molecules (not shown) that have either positive or negative dielectric anisotropy depending on the mode of display, and a chiral agent as needed.
In the liquid crystal display device 100 with such a structure, a liquid crystal capacitor CLC is formed by the pixel electrode 11, the counter electrode 21 that faces the pixel electrode 11, and the liquid crystal layer 30 interposed between them. Also, a storage capacitor CCS is formed by the storage capacitor electrode 17, the storage capacitor counter electrode 15a that faces the storage capacitor electrode 17, and the gate insulating film 16 interposed between them. And a pixel capacitor Cpix is formed by the liquid crystal capacitor CLC and the storage capacitor CCS that is arranged in parallel to the liquid crystal capacitor CLC.
As shown in
In the liquid crystal display device 100 of this embodiment, the respective bent portions 13c of two arbitrary ones of the signal lines 13, which are adjacent to each other in the row direction, are arranged at mutually different positions in the column direction as shown in
Specifically, the bent portion 13c of the left one of the two signal lines 13 that are adjacent to the red pixel R (i.e., its own source for the pixel electrode 11 of the red pixel R) is located under the middle of the pixel in the column direction. On the other hand, the bent portion 13c of the other, right signal line 13 (i.e., other's source for the pixel electrode 11 of the red pixel R) is located over the middle of the pixel in the column direction. Meanwhile, the bent portion 13c of the left one of the two signal lines 13 that are adjacent to the green pixel G (i.e., its own source for the pixel electrode 11 of the green pixel G) is located over the middle of the pixel in the column direction. On the other hand, the bent portion 13c of the other, right signal line 13 (i.e., other's source for the pixel electrode 11 of the green pixel G) is located under the middle of the pixel in the column direction.
Furthermore, the bent portion 13c of the left one of the two signal lines 13 that are adjacent to the blue pixel B (i.e., its own source for the pixel electrode 11 of the blue pixel B) is located under the middle of the pixel in the column direction. On the other hand, the bent portion 13c of the other, right signal line 13 (i.e., other's source for the pixel electrode 11 of the blue pixel B) is located over the middle of the pixel in the column direction. Meanwhile, the bent portion 13c of the left one of the two signal lines 13 that are adjacent to the yellow pixel Y (i.e., its own source for the pixel electrode 11 of the yellow pixel Y) is located over the middle of the pixel in the column direction. On the other hand, the bent portion 13c of the other, right signal line 13 (i.e., other's source for the pixel electrode 11 of the yellow pixel Y) is located under the middle of the pixel in the column direction.
If the bent portions 13c are arranged in this manner, the area of overlap between the pixel electrode 11 of the larger pixel (which is either the red pixel R or the blue pixel B) and the signal line 13 (i.e., its own source) that supplies a grayscale voltage to that pixel electrode 11 is greater than the area of overlap between the pixel electrode 11 of the smaller pixel (which is either the green pixel G or the yellow pixel Y) and a signal line 13 (its own source) that supplies a grayscale voltage to that pixel electrode 11. That is why the source-drain capacitance Csd of the larger pixel is greater than the source-drain capacitance Csd of the smaller pixel. As a result, the difference in the magnitude of variation ΔV (which is represented by Equation (1)) in drain voltage can be reduced, and it is possible to avoid an unwanted situation where the voltages applied to the liquid crystal layer 30 have significantly different effective values between the larger and smaller pixels.
As described above, in the liquid crystal display device 100 of this embodiment, by arranging the respective bent portions 13c at two different positions in the column direction between two adjacent signal lines 13, the source-drain capacitance Csd of the larger pixel becomes different from that of the smaller pixel. As a result, the variation in the effective voltage applied to the liquid crystal layer 30 can be reduced significantly.
In order to reduce the difference in ΔV between the larger and smaller pixels, the difference between the Csd/Cpix ratio (which is sometimes called a “β value”) of the source-drain capacitance Csd of the larger pixel to the pixel capacitance Cpix and the Csd/Cpix ratio of the source-drain capacitance Csd of the smaller pixel to the pixel capacitance Cpix needs to be as small as possible. Specifically, it would be beneficial if the difference is 15% or less. And it would be more beneficial if the respective β values (i.e., Csd/Cpix values) of the larger and smaller pixels are substantially equal to each other. If the respective β values of the larger and smaller pixels are substantially equal to each other (specifically, if their difference is within ±5%), ΔV can be substantially equal between the larger and smaller pixels.
Strictly speaking, there are two different kinds of source-drain capacitances Csd, namely, a parasitic capacitance between its own source and the drain (which will be identified herein by “Csd(self)”) and a parasitic capacitance between other's source and the drain (which will be identified herein by “Cs(other)”). If a display operation is conducted in a single color, the potential at a pixel electrode 11 (i.e., the pixel electrode 11 of a lighted pixel) is affected by only a voltage variation at its own source. That is to say, the signal on the other's source does not vary. That is why in this description, the source-drain capacitance Csd always refers herein to its own source-drain capacitance Csd(self) unless otherwise stated.
On the other hand, if the display operation is conducted in mixed colors (i.e., if the signals on its own source and other's source both vary), the potential at the pixel electrode 11 is affected by a variation in voltage not only on its own source but also on other's source as well. That is why in order to cancel their influences (because voltages of opposite polarities are supplied to its own source and other's source in the case of the source line inversion drive and dot inversion drive), it would be advantageous if its own source-drain capacitance Csd(self) is substantially equal to other's source-drain capacitance Csd(other). For that reason, as shown in
In the embodiment described above, the red and blue pixels R and B are supposed to be the larger pixels and the green and yellow pixels G and Y are supposed to be the smaller pixels. However, this is only an example of the present invention and that combination does not always have to be adopted. Rather it may be determined appropriately according to the intended use or specification of the liquid crystal display device which pixels may have the larger (or smaller) area than the others. If the red pixel R is the larger pixel as in this embodiment, the lightness of the color red increases and a bright red can be represented, which is beneficial.
Also, in the embodiment described above, multiple pixels are arranged in one row and multiple columns in each picture element P. However, those pixels may also be arranged in multiple rows and multiple columns in each picture element P as shown in
Hereinafter, a liquid crystal display device 200 as a second embodiment of the present invention will be described with reference to
In each picture element P, those four pixels are arranged in the order of red, green, blue and yellow pixels R, G, B and Y from the left to the right. Thus, those larger, larger, larger and smaller pixels are repeatedly arranged in this order in the row direction.
In this liquid crystal display device 200, the respective bent portions 13c of two arbitrary ones of the signal lines 13, which are adjacent to each other in the row direction, are also arranged at mutually different positions in the column direction. Thus, the area of overlap between the pixel electrode 11 of the larger pixel (which is the red, green or blue pixel R, G or B) and the signal line 13 (i.e., its own source) that supplies a grayscale voltage to that pixel electrode 11 is greater than the area of overlap between the pixel electrode 11 of the smaller pixel (which is the yellow pixel Y) and a signal line 13 (its own source) that supplies a grayscale voltage to that pixel electrode 11. That is why the source-drain capacitance Csd of the larger pixel is greater than the source-drain capacitance Csd of the smaller pixel. As a result, the difference in the magnitude of variation ΔV in drain voltage between the larger and smaller pixels can be reduced, and it is possible to avoid an unwanted situation where the voltages applied to the liquid crystal layer 30 have significantly different effective values between the larger and smaller pixels.
In this liquid crystal display device 200, the areas of overlap between the pixel electrode 11 and their own source are different among the three larger pixels of each picture element P. That is why among those three larger pixels, their own source-drain capacitances Csd(self) do not agree with each other, neither do the magnitudes ΔV of variation in drain voltage. However, the display quality will be affected by not just the variation in ΔV but also the absolute value of ΔV as well. For that reason, even if ΔV varied to a certain degree among those larger pixels, ΔV of the smaller pixel would rather be reduced than be much greater than that of the larger pixels.
On top of that, in this liquid crystal display device 200, the sum of the area of overlap between their own source and the pixel electrode 11 and the area of overlap between other's source and the pixel electrode 11 is substantially the same between those three larger pixels of each picture element P. That is why the sum of their own source-drain capacitance Csd(self) and other's source-drain capacitance Csd(other) is substantially the same between those three larger pixels. Consequently, the pixel charge rate and the influence of the voltage variation (ΔVd) due to a feedthrough phenomenon of a gate signal can be the same between those larger pixels, which is beneficial.
Hereinafter, a liquid crystal display device 300 as a third embodiment of the present invention will be described with reference to
In this liquid crystal display device 300, the respective bent portions 13c of two arbitrary ones of the signal lines 13, which are adjacent to each other in the row direction, are also arranged at mutually different positions in the column direction. Thus, the area of overlap between the pixel electrode 11 and the signal line 13 (i.e., its own source) that supplies a grayscale voltage to that pixel electrode 11 is greater in the blue pixel B than in the red pixel R and even greater in the green pixel G than in the blue pixel B. Consequently, the source-drain capacitance Csd of the blue pixel R is greater than that of the red pixel R and the source-drain capacitance Csd of the green pixel G is even greater than that of blue pixel B.
As can be seen, even if the respective pixels have the same area, the source-drain capacitance Csd of each of those pixels can be set to be an arbitrary value by arranging the bent portions 13a of two adjacent signal lines 13 at mutually different positions in the column direction. As the color green achieves higher luminous efficacy than the color red or blue does, a display defect, if any, is more easily sensible to the eye at a green pixel G than at a red pixel R or a blue pixel B when the effective value of the voltage applied to the liquid crystal layer changes. That is why by setting the source-drain capacitance Csd of the green pixel G to be smaller than that of any other pixel (as opposed to the configuration shown in
Hereinafter, a liquid crystal display device 400 as a fourth embodiment of the present invention will be described with reference to
As shown in
If the width of each signal line 13 changes at its bent portion 13c as described above, the area of overlap between the pixel electrode 11 of the larger pixel (which is the red or blue pixel R or B) and the signal line 13 (their own source) that supplies a grayscale voltage to that pixel electrode 11 is greater than the area of overlap between the pixel electrode 11 of the smaller pixel (which is the green or yellow pixel G or Y) and the signal line 13 (their own source) that supplies a grayscale voltage to that pixel electrode 11. That is why the source-drain capacitance Csd of the larger pixel is greater than the source-drain capacitance Csd of the smaller pixel. As a result, the difference in the magnitude of variation ΔV in drain voltage between the larger and smaller pixels can be reduced, and it is possible to avoid an unwanted situation where the voltages applied to the liquid crystal layer 30 have significantly different effective values between the larger and smaller pixels.
As described above, in the liquid crystal display device 400 of this embodiment, by setting the respective widths of the first and second straight portions 13a and 13b of each signal line 13 to be different from each other, the source-drain capacitance Csd of the larger pixels can be different from that of the smaller pixels. As a result, the variation in the effective voltage applied to the liquid crystal layer can be reduced significantly.
In the arrangement illustrated in
Furthermore, even in the arrangement shown in
Hereinafter, a liquid crystal display device 500 as a fifth embodiment of the present invention will be described with reference to
In this liquid crystal display device 500, the respective bent portions 13c of two arbitrary ones of the signal lines 13, which are adjacent to each other in the row direction, are also arranged at mutually different positions in the column direction. Also, the first and second straight portions 13a and 13b of each of those signal lines 13 have mutually different widths. Specifically, as for the red R and blue B pixels' (i.e., the larger pixels') own source, the first straight portion 13a is relatively broad and the second straight portion 13b is relatively narrow. On the other hand, as for the green G and yellow Y pixels' (i.e., the smaller pixels') own source, the first straight portion 13a is relatively narrow and the second straight portion 13b is relatively broad.
As described above, in the liquid crystal display device 500 of this embodiment, the configuration in which the bent portions 13c of two adjacent signal lines 13 are arranged at different positions in the column direction and the configuration in which the width of the signal line 13 is changed at its bent portion 13c are combined, thereby setting the source-drain capacitances Csd of the larger and smaller pixels to be different from each other. As a result, the variation in the effective voltage applied to the liquid crystal layer can be reduced significantly.
In the example illustrated in
Still alternatively, even if the respective pixels have the same area as shown in
A liquid crystal display device as a sixth embodiment of the present invention can carry out a multi-pixel drive (pixel division drive) operation. By adopting the multi-pixel drive, the viewing angle dependence of the γ (gamma) characteristic, which refers to a phenomenon that the γ characteristic when the screen is viewed straight on is different from the characteristic when it is viewed obliquely, can be reduced significantly. In this case, the “γ characteristic” refers to the grayscale dependence of display luminance. According to the multi-pixel drive, a single pixel is made up of multiple subpixels that can display mutually different luminances, thereby displaying a predetermined luminance associated with a display signal that has been supplied to the pixel. That is to say, the multi-pixel drive is a technique for reducing the viewing angle dependence of the γ characteristic of a pixel by synthesizing together the mutually different γ characteristics of multiple subpixels thereof.
The pixel electrode 11 of each pixel also has two subpixel electrodes 11A and 11B, which are associated with the two subpixels sp1 and sp2, respectively, and which are connected to their associated TFTs 14A and 14B, respectively.
The respective gate electrodes of the two TFTs 14A and 14B are connected in common to the same scan line 12 and have their ON and OFF states controlled with the same gate signal. Also, the respective source electrodes of the two TFTs 14A and 14B are connected in common to the same signal line 13.
A storage capacitor is provided for each of the two subpixels sp1 and sp2. The storage capacitor electrode 17 that forms part of the storage capacitor of one subpixel sp1 is electrically connected to the drain electrode of the TFT 14A. On the other hand, the storage capacitor electrode 17 that forms part of the storage capacitor of the other subpixel sp2 is electrically connected to the drain electrode of the TFT 14B. Also, the storage capacitor counter electrode 15a that forms another part of the storage capacitor of the subpixel sp1 is electrically connected to the storage capacitor line 15A. On the other hand, the storage capacitor counter electrode 15a that forms another part of the storage capacitor of the subpixel sp2 is electrically connected to the storage capacitor line 15B. The respective storage capacitor counter electrodes 15a of the subpixels sp1 and sp2 are independent of each other and are supplied with mutually different voltages (i.e., storage capacitor counter voltages) through the storage capacitor lines 15A and 15B, respectively. By changing the storage capacitor counter voltages applied to the storage capacitor counter electrodes 15a, mutually different effective voltages can be applied to the respective liquid crystal layers 30 of the subpixels sp1 and sp2 by utilizing the capacitance division technique. As a result, the subpixels sp1 and sp2 can have mutually different display luminances.
The liquid crystal display devices 600A through 600E of this embodiment also have the configuration in which the bent portions 13c of two adjacent signal lines 13 are arranged at different positions in the column direction and/or the configuration in which the width of the signal line 13 is changed at its bent portion 13c (i.e., the signal line 13 has portions with two different widths).
Just like each set of pixels of the liquid crystal display device 100 of the first embodiment described above, each set of pixels of the liquid crystal display device 600A shown in
Each signal line 13 of the liquid crystal display device 600A has a set of first and second straight portions 13a and 13b and bent portion 13c in an area allocated to the one subpixel sp1 and also has further set of first and second straight portions 13a and 13b and bent portion 13c in an area allocated to the other subpixel sp2.
As shown in
Just like each set of pixels of the liquid crystal display device 200 of the second embodiment described above, each set of pixels of the liquid crystal display device 600B shown in
As shown in
In the liquid crystal display devices 600A and 600B shown in
In the liquid crystal display device 600C shown in
As shown in
In this liquid crystal display device 600C, the respective bent portions 13c (i.e., the bent portions 13c provided for the subpixels sp1) of two arbitrary ones of the signal lines 13, which are adjacent to each other in the row direction, are also arranged at mutually different positions in the column direction. Thus, the area of overlap between the subpixel electrode 11A and the signal line 13 (i.e., its own source) that supplies a grayscale voltage to that subpixel electrode 11A is greater in the blue pixel B than in the red pixel R and even greater in the green pixel G than in the blue pixel B. Consequently, the source-drain capacitance Csd of the blue pixel R is greater than that of the red pixel R and the source-drain capacitance Csd of the green pixel G is even greater than that of blue pixel B.
As can be seen, even if the respective pixels have the same area, the source-drain capacitance Csd of each of those pixels can be set to be an arbitrary value by arranging the bent portions 13a of two adjacent signal lines 13 at mutually different positions in the column direction.
In the liquid crystal display device 600C shown in
Just like each set of pixels of the liquid crystal display device 400 of the fourth embodiment, each set of pixels of the liquid crystal display device 600D shown in
As shown in
Thus, the area of overlap between the pixel electrode 11 of the larger pixel (which is the red or blue pixel R or B) and the signal line 13 (their own source) that supplies a grayscale voltage to that pixel electrode 11 is greater than the area of overlap between the pixel electrode 11 of the smaller pixel (which is the green or yellow pixel G or Y) and the signal line 13 (their own source) that supplies a grayscale voltage to that pixel electrode 11. That is why the source-drain capacitance Csd of the larger pixel is greater than the source-drain capacitance Csd of the smaller pixel. As a result, the difference in the magnitude of variation ΔV in drain voltage between the larger and smaller pixels can be reduced, and it is possible to avoid an unwanted situation where the voltages applied to the liquid crystal layer have significantly different effective values between the larger and smaller pixels.
Just like each set of pixels of the liquid crystal display device 500 of the fifth embodiment described above, each set of pixels of the liquid crystal display device 600E shown in
In this liquid crystal display device 600E, the respective bent portions 13c of two arbitrary ones of the signal lines 13, which are adjacent to each other in the row direction, are also arranged at mutually different positions in the column direction as shown in
As described above, in the liquid crystal display device 600E of this embodiment, the configuration in which the bent portions 13c of two adjacent signal lines 13 are arranged at different positions in the column direction and the configuration in which the width of the signal line 13 is changed at its bent portion 13c are combined, thereby setting the source-drain capacitances Csd of the larger and smaller pixels to be different from each other. As a result, the variation in the effective voltage applied to the liquid crystal layer can be reduced significantly.
In the first through sixth embodiments of the present invention described above, one picture element P is supposed to be defined by four or three pixels as an example. However, the present invention is in no way limited to those specific embodiments. Optionally, each picture element P may also be defined by six pixels as shown in
As for the respective kinds (i.e., the combination) of pixels that define a single picture element P, the combinations described above are just examples, too. For example, if each picture element P is defined by four pixels, each picture element P may be defined by either red, green, blue and cyan pixels R, G, B and C or red, green, blue and magenta pixels R, G, B and M. Alternatively, each picture element P may also be defined by red, green, blue and white pixels R, G, B and W as shown in
According to the present invention, the source-drain capacitance Csd can be set to be an arbitrary value on a pixel-by-pixel basis in a liquid crystal display device. The present invention is applicable to a multi-primary-color liquid crystal display device and can be used particularly effectively in a configuration in which pixels with mutually different areas are included in the same mix.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-285567 | Dec 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/072253 | 12/10/2010 | WO | 00 | 6/14/2012 |
