U.S. patent application number 13/627544 was filed with the patent office on 2013-04-11 for color liquid crystal display device and gamma correction method for the same.
The applicant listed for this patent is Kentaro IRIE, Fumikazu SHIMOSHIKIRYOH. Invention is credited to Kentaro IRIE, Fumikazu SHIMOSHIKIRYOH.
Application Number | 20130088527 13/627544 |
Document ID | / |
Family ID | 38005542 |
Filed Date | 2013-04-11 |
United States Patent
Application |
20130088527 |
Kind Code |
A1 |
IRIE; Kentaro ; et
al. |
April 11, 2013 |
Color Liquid Crystal Display Device And Gamma Correction Method For
The Same
Abstract
A color liquid crystal display device configured to employ a
pixel division method in which each pixel of a displayed image is
configured with sub-pixels obtained by spatial division of one
pixel in a division ratio may include: pixel formation portions
provided correspondingly to respective pixels of the image, each
portion configured to form a pixel of primary colors with the
sub-pixels; a drive circuit configured to provide each portion with
applied voltages respectively corresponding to the sub-pixels
composing the pixel to be formed by that portion, based on a
gradation value indicated by an input signal provided as a video
signal representing the image; and a gamma correction part
configured to correct a relationship between the gradation value
indicated by the input signal and a luminance value of the pixel to
be formed by that portion according to the gradation value
independently for each of the primary colors.
Inventors: |
IRIE; Kentaro; (Mie, JP)
; SHIMOSHIKIRYOH; Fumikazu; (Mie, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IRIE; Kentaro
SHIMOSHIKIRYOH; Fumikazu |
Mie
Mie |
|
JP
JP |
|
|
Family ID: |
38005542 |
Appl. No.: |
13/627544 |
Filed: |
September 26, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12083011 |
Apr 3, 2008 |
8305316 |
|
|
PCT/JP2006/310853 |
May 31, 2006 |
|
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13627544 |
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Current U.S.
Class: |
345/690 ;
345/87 |
Current CPC
Class: |
G09G 3/3648 20130101;
G09G 2320/0276 20130101; G09G 2320/0285 20130101; G02F 2001/134354
20130101; G09G 2320/028 20130101; G09G 2320/0673 20130101; G09G
2300/0439 20130101; G09G 2300/0443 20130101; G02F 2001/134345
20130101; G09G 2300/0452 20130101; G09G 2320/0242 20130101 |
Class at
Publication: |
345/690 ;
345/87 |
International
Class: |
G09G 3/36 20060101
G09G003/36 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2005 |
JP |
2005-316676 |
Claims
1-10. (canceled)
11. A color liquid crystal display device configured to employ a
pixel division method in which each pixel of an image displayed in
a screen is configured with two or more sub-pixels obtained by
spatial division of one pixel in a division ratio, the device
comprising: a plurality of pixel formation portions provided
correspondingly to respective pixels of the image, each of the
pixel formation portions configured to form a pixel of any of
primary colors for color display with the two or more sub-pixels; a
drive circuit configured to provide each of the pixel formation
portions with applied voltages respectively corresponding to the
two or more sub-pixels composing the pixel to be formed by that
pixel formation portion, based on a gradation value indicated by an
input signal provided from outside as a video signal representing
the image; and a gamma correction part configured to correct a
relationship between the gradation value indicated by the input
signal and a luminance value of the pixel to be formed by that
pixel formation portion according to the gradation value
independently for each of the primary colors for color display;
wherein each of the pixel formation portions forms the respective
pixel by displaying the two or more sub-pixels with luminance
values different from one another based on the applied voltages,
and wherein the gamma correction part corrects the relationship
such that gradation dependence of chromaticity is suppressed when
the screen is viewed from a front thereof, and also corrects the
relationship in a vicinity of a predetermined gradation value such
that the gradation dependence of chromaticity is suppressed when
the screen is viewed from an oblique direction, the predetermined
gradation value being determined by an area ratio of the two or
more sub-pixels in the one pixel and differences in the applied
voltages among the two or more sub-pixels.
12. The color liquid crystal display device of claim 11, wherein
the gamma correction part is configured to correct the chromaticity
when viewed from the front to be shifted from a state maintaining a
color balance toward blue in the vicinity of the gradation value
such that the gradation dependence of chromaticity is suppressed
when viewed from the oblique direction.
13. The color liquid crystal display device of claim 11, wherein
the gamma correction part is configured to correct the relationship
such that a curve representing the gradation dependence of
chromaticity when viewed from the front becomes approximately flat
in a range except for the vicinity of the gradation value.
14. The color liquid crystal display device of claim 11, wherein
the gamma correction part is configured to correct the relationship
such that a curve representing the gradation dependence of
chromaticity when viewed from the front changes approximately
monotonically with respect to the gradation value.
15. The color liquid crystal display device of claim 11, wherein
the gamma correction part includes a correction table associating a
gradation value before correction with a gradation value after
correction for each of the primary colors for color display in
order to correct the relationship, and outputs the gradation value
after correction associated with the gradation value indicated by
the input signal referring to the correction table, and wherein the
drive circuit is further configured to provide each of the pixel
formation portions with the applied voltages based on the gradation
value after correction.
16. A gamma correction method for correcting a relationship between
a gradation value indicated by an input signal provided from
outside as a video signal representing an image and a luminance
value of a pixel formed according to the gradation value, in a
color liquid crystal display device employing a pixel division
method in which each pixel of the image displayed on a screen is
composed of two or more sub-pixels obtained by spatial division of
one pixel in a division ratio, the method comprising: a correction
to correct the relationship independently for each of primary
colors for color display; wherein in the correction, the
relationship is corrected such that gradation dependence of
chromaticity is suppressed when the screen is viewed from a front
thereof, and the relationship in a vicinity of a predetermined
gradation value is also corrected such that the gradation
dependence of chromaticity is suppressed when the screen is viewed
from an oblique direction, the predetermined gradation value being
determined by an area ratio of the two or more sub-pixels in the
one pixel and differences in voltages applied to liquid crystal of
the color liquid crystal display device among the two or more
sub-pixels.
17. The gamma correction method of claim 16, wherein in the
correction, the chromaticity when viewed from the front is
corrected to shift from a state maintaining a color balance toward
blue in the vicinity of the gradation value such that the gradation
dependence of chromaticity is suppressed when viewed from the
oblique direction.
18. The gamma correction method of claim 16, wherein in the
correction, the relationship is corrected such that a curve
representing the gradation dependence of chromaticity when viewed
from the front becomes approximately flat in a range except for the
vicinity of the gradation value.
19. The gamma correction method of claim 16, wherein in the
correction, the relationship is corrected such that a curve
representing the gradation dependence of chromaticity when viewed
from the front changes approximately monotonically with respect to
the gradation value.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/083,011, filed on Apr. 3, 2008, in the U.S. Patent and
Trademark Office, the entire contents of which are incorporated
herein by reference. U.S. patent application Ser. No. 12/083,011 is
a national stage entry from International Application No.
PCT/JP2006/310853, filed on May 31, 2006 (and amended on Feb. 16,
2007), in the Receiving Office of the Japan Patent Office, the
entire contents of which are also incorporated herein by reference.
International Application No. PCT/JP2006/310853 claims priority
from Japanese Patent Application No. 2005-316676, filed on Oct. 31,
2005, in the Japan Patent Office (JPO), the entire contents of
which are additionally incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a color liquid crystal
display device employing a pixel division method, in which each
pixel of a displayed image is composed of a predetermined number of
two or more sub-pixels obtained by spatial or temporal division of
one pixel, and more specifically to an improvement of color
reproducibility in such a color liquid crystal display device.
BACKGROUND ART
[0003] Usually in a display device, for the purpose of a good
reproduction of an image represented by a video signal provided
from outside as an input signal, gradation or the like indicated by
the input signal is corrected for adjusting a relationship between
a gradation value indicated by the input signal and a luminance
value of an image actually displayed. Such correction is called
"gamma correction".
[0004] A liquid crystal display device displays an image
represented by an input signal by controlling an applied voltage of
liquid crystal according to the input signal and thereby changing
light transmittance of the liquid crystal. In such a liquid crystal
display device, the gamma correction is also carried out by
correcting the gradation value or the like indicated by the input
signal according to a relationship between the applied voltage and
the transmittance of the liquid crystal (hereinafter, referred to
as "VT characteristics").
[0005] Meanwhile, the liquid crystal display device controls the
transmittance by applying a voltage across a liquid crystal layer
sandwiched between a pair of polarizer plates and thereby changing
a phase difference (retardation) of the liquid crystal layer.
Recently, a vertical alignment (VA) mode of the liquid crystal is
used for an application to a television (TV) and a monitor, which
is a normally black mode showing a black image without the applied
voltage and provides a high quality black image and a high
contrast. In this VA mode, the retardation of the liquid crystal
has a wavelength dependence. Therefore, in a color liquid crystal
display device which displays a color image using three kinds of
pixels, R (red), G (green), and B (blue), the VT characteristics
are slightly different among the three kinds of pixels.
[0006] Accordingly, there has been conventionally proposed a liquid
crystal display device which carries out the gamma correction
independently for each R, G, and B for obtaining a good color
reproducibility in a displayed image (hereinafter, such a gamma
correction carried out independently for each R, G, and B is
referred to as "RGB independent gamma correction", or simply
"independent gamma correction"). For example, Japanese Unexamined
Patent Application Publication No. 2002-258813 (patent reference 1)
discloses a color liquid crystal display device which determines
.gamma.-curves of R, G, and B individually by generating gradation
voltages independently for each R, G, and B (carries out the
independent gamma correction). Also, Japanese
[0007] Unexamined Patent Application Publication No. 2001-222264
(patent reference 2) discloses a liquid crystal display device
including a storage means for storing gamma correction data for R,
G, and B generated on the basis of each luminance characteristics
of an R pixel, G pixel, and B pixel arranged in a matrix on a
liquid crystal panel, and a gamma correction means for individually
correcting an R signal, G signal, and B signal composing a video
signal to be supplied to the R pixel, G pixel, and B pixel,
respectively, on the basis of the gamma correction data for R, G,
and B (carrying out the independent gamma correction). [0008]
Patent reference 1: Japanese Unexamined Patent Application
Publication No. 2002-258813 [0009] Patent reference 2: Japanese
Unexamined Patent Application Publication No. 2001-222264 [0010]
Patent reference 3: Japanese Unexamined Patent Application
Publication No. 2004-78157 [0011] Patent reference 4: Japanese
Unexamined Patent Application Publication No. 2004-62146 [0012]
Patent reference 5: Japanese Unexamined Patent Application
Publication No. 2005-173573
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0013] In a liquid crystal display device using a VA mode,
.gamma.-characteristics are different between a case where a
display screen is viewed from the front thereof (in a front view)
and a case where the display screen is viewed with an angle (in an
oblique view). Therefore, the transmittance of the liquid crystal
in the oblique view becomes higher than that in the front view and
display on the screen appears as floating in white (white
floating). Various methods have been proposed for improving such
white floating in the oblique view (more generally, for improving a
viewing angle dependence of the .gamma.-characteristics).
[0014] For example, Japanese Unexamined Patent Application
Publication No. 2004-78157 (patent reference 3) and Japanese
Unexamined Patent Application Publication No. 2004-62146 (patent
reference 4) disclose liquid crystal display devices employing a
pixel division method which can improve the viewing angle
dependence of the .gamma.-characteristics representing a
relationship between the gradation value and the display luminance
value. Each of these liquid crystal display devices employing the
pixel division method has a plurality of pixels arranged in a
matrix, each having a liquid crystal layer and a plurality of
electrodes for applying voltages on the liquid crystal layer. Each
of the plurality of pixels has a first sub-pixel and a second
sub-pixel where voltages different from each other can be applied
on the liquid crystal layer, respectively. In such a configuration,
a luminance value (or transmittance value) of each pixel is
provided on the basis of luminance values (or transmittance values)
different from each other in the first sub-pixel and the second
sub-pixel, respectively. Providing a difference of the luminance
(or transmittance) between sub-pixels in one pixel in this manner
improves the viewing angle dependence of the
.gamma.-characteristics.
[0015] Here, while each pixel is divided spatially into the
plurality of sub-pixels (the first sub-pixel and the second
sub-pixel) in these liquid crystal display devices, instead each
pixel may be configured to be divided temporally into a plurality
of sub-pixels, that is, may be configured such that one frame
period is divided into a plurality of sub-frames, a luminance
difference is provided among the plurality of sub-frame periods,
and an average luminance value of the plurality of sub-frame
periods becomes a luminance value of each pixel (refer to e.g.,
Japanese Unexamined Patent Application Publication No. 2005-173573
(patent reference 5)). A temporal pixel division method as in the
latter case also can improve the viewing angle dependence of the
.gamma.-characteristics.
[0016] Also in the liquid crystal display device employing the
pixel division method (spatial or temporal) as described above, the
independent gamma correction is carried out and a gradation
dependence of chromaticity is suppressed to obtain a good color
reproducibility in displaying an image. In the pixel division
method, however, even if the chromaticity is adjusted not to change
depending on the gradation, that is, good chromaticity
characteristics maintaining a color balance are obtained in an
almost whole gradation range when a screen of the liquid crystal
display device is viewed from a front direction, the chromaticity
still changes depending on gradation values in a certain range of
halftone when the screen is viewed from a oblique direction, as
shown in FIG. 10. As a result, even in a case where the gradation
value is changed such that each of the three primary colors, R, G,
and B is mutually the same, that is, even in a case where the
gradation value is changed such that the screen exhibits an
achromatic color when viewed from the front direction as shown in
(A) of FIG. 17, there is caused a phenomenon that the screen is
tinged with yellow in a certain range of the halftone when the
screen is viewed in the oblique direction, as shown in (B) of FIG.
17. This means that the good color reproducibility can not be
obtained when the screen is viewed in the oblique direction.
[0017] Accordingly, an object of the present invention is to
provide a color liquid crystal display device which can display an
image having a high color reproducibility when viewed from an
oblique direction as well as from a front direction of a screen
thereof, while improving the viewing angle dependence of the
.gamma.-characteristics by employing the pixel division method.
Measures for Solving the Problems
[0018] In a first aspect of the present invention, there is
provided a color liquid crystal display device, employing a pixel
division method in which each pixel of an image displayed in a
predetermined screen is configured with a predetermined number of
two or more sub-pixels obtained by spatial or temporal division of
one pixel in a predetermined division ratio, the device
comprising:
[0019] a plurality of pixel formation portions provided
correspondingly to respective pixels of the image, each of the
portions forming a pixel of any of primary colors for color display
with the predetermined number of sub-pixels;
[0020] a drive circuit for providing each of the pixel formation
portions with applied voltages respectively corresponding to the
sub-pixels composing the pixel to be formed by that pixel formation
portion, based on a gradation value indicated by an input signal
provided from outside as a video signal representing the image;
and
[0021] a gamma correction part for correcting a relationship
between a gradation value indicated by the input signal and a
luminance value of the pixel formed by the pixel formation portion
according to the gradation value independently for each of the
primary colors for color display,
[0022] wherein each of the pixel formation portions forms the pixel
by displaying the predetermined number of sub-pixels with luminance
values different from one another based on the applied voltages,
and
[0023] wherein the gamma correction part corrects the relationship
such that gradation dependence of chromaticity is suppressed when
the screen is viewed from a front thereof, and also corrects the
relationship in the vicinity of a predetermined gradation value,
which is determined by the division ratio in the one pixel and
differences in the applied voltage among the predetermined number
of sub-pixels, such that the gradation dependence of the
chromaticity is suppressed when the screen is viewed from a
predetermined oblique direction.
[0024] In a second aspect of the present invention, there is
provided the color liquid crystal display device according to the
first aspect of the present invention, wherein the gamma correction
part corrects the chromaticity when viewed from the front to be
shifted from a state maintaining a color balance toward blue in the
vicinity of the predetermined gradation value such that the
gradation dependence of the chromaticity is suppressed when viewed
from the oblique direction.
[0025] In a third aspect of the present invention, there is
provided the color liquid crystal display device according to the
first aspect of the present invention, wherein the gamma correction
part corrects the relationship such that a curve representing the
gradation dependence of the chromaticity when viewed from the front
becomes approximately flat in a range except for the vicinity of
the predetermined gradation value.
[0026] In a fourth aspect of the present invention, there is
provided the color liquid crystal display device according to the
first aspect of the present invention, wherein the gamma correction
part corrects the relationship such that a curve representing the
gradation dependence of the chromaticity when viewed from the front
changes approximately monotonically with respect to the gradation
value.
[0027] In a fifth aspect of the present invention, there is
provided the color liquid crystal display device according to the
first aspect of the present invention, wherein the gamma correction
part includes a correction table associating a gradation value
before correction with a gradation value after correction for each
of the primary colors for color display in order to correct the
relationship, and outputs the gradation value after correction
associated with the gradation value indicated by the input signal
referring to the correction table, and
[0028] wherein the drive circuit provides each of the pixel
formation portions with the applied voltage based on the gradation
value after correction.
[0029] In a sixth aspect of the present invention, there is
provided the color liquid crystal display device according to the
first aspect of the present invention, further including
[0030] a common electrode provided commonly at the plurality of
pixel formation portions,
[0031] each of the pixel formation portions including:
[0032] a first and a second sub-pixel electrodes disposed facing
the common electrode so as to sandwich a liquid crystal layer in
between;
[0033] a first auxiliary electrode disposed so as to form a first
auxiliary capacitance between the first sub-pixel electrode and the
same; and
[0034] a second auxiliary electrode disposed so as to form a second
auxiliary capacitance between the second sub-pixel electrode and
the same, and
[0035] the drive circuit including:
[0036] a pixel electrode drive circuit for providing a voltage
according to the input signal to the first and second sub-pixel
electrodes with the common electrode as a reference; and
[0037] an auxiliary electrode drive circuit for applying voltages
which are different from each other and changes in a predetermined
period and a predetermined amplitude, to the first and second
auxiliary electrodes,
[0038] wherein the predetermined gradation value is determined by
an area ratio of the first sub-pixel electrode to the second
sub-pixel electrode and a difference in the applied voltage between
the first auxiliary electrode and the second auxiliary
electrode.
[0039] In a seventh aspect of the present invention, there is
provided a gamma correction method for correcting a relationship
between a gradation value indicated by an input signal provided
from outside as a video signal representing an image and a
luminance value of a pixel formed according to the gradation value,
in a color liquid crystal display device employing a pixel division
method in which each pixel of the image displayed on a
predetermined screen is composed of a predetermined number of two
or more sub-pixels obtained by spatial or temporal division of one
pixel in a predetermined division ratio, the method including
[0040] a correction step of correcting the relationship
independently for each of primary colors for color display,
[0041] wherein in the correction step, the relationship is
corrected such that gradation dependence of chromaticity is
suppressed when the screen is viewed from a front thereof, and the
relationship in the vicinity of a predetermined gradation value is
also corrected such that the gradation dependence of the
chromaticity is suppressed when the screen is viewed from a
predetermined oblique direction, the predetermined gradation value
being determined by the division ratio in the one pixel and
differences in a voltage applied to liquid crystal among the
predetermined number of sub-pixels.
[0042] In an eighth aspect of the present invention, there is
provided the gamma correction method according to the seventh
aspect of the present invention, wherein in the correction step,
the chromaticity when viewed from the front is corrected to shift
from a state maintaining a color balance toward blue in the
vicinity of the predetermined gradation value such that the
gradation dependence of the chromaticity is suppressed when viewed
from the oblique direction.
[0043] In a ninth aspect of the present invention, there is
provided the gamma correction method according to the seventh
aspect of the present invention, wherein in the correction step,
the relationship is corrected such that a curve representing the
gradation dependence of the chromaticity when viewed from the front
becomes approximately flat in a range except for the vicinity of
the predetermined gradation value.
[0044] In a tenth aspect of the present invention, there is
provided the gamma correction method according to the seventh
aspect of the present invention, wherein in the correction step,
the relationship is corrected such that a curve representing the
gradation dependence of the chromaticity when viewed from the front
changes approximately monotonically with respect to the gradation
value.
Advantages of the Invention
[0045] According to the first aspect of the present invention, an
independent gamma correction is carried out such that the gradation
dependence of the chromaticity is suppressed when the screen is
viewed from the front of the screen (in the front view), and also
the independent gamma correction is carried out in the vicinity of
the predetermined gradation value, which is determined by the
division ratio in one pixel and differences in the applied voltage
among the predetermined number of sub-pixels in one pixel, such
that the gradation dependence of the chromaticity is suppressed
when the screen is viewed from a predetermined oblique direction
(in the oblique view). Such an independent gamma correction
suppresses color imbalance in the range of the halftone observed in
the conventional color liquid crystal display device employing the
pixel division method to such an extent that matters little for a
human visual sense even in the oblique view, and there is obtained
a situation in which the color balance is maintained substantially
for the almost whole gradation range in the oblique view as well as
in the front view (to the extent that matters little for a human
visual sense). As a result, it is possible to display an image
having a high color reproducibility when viewed from an oblique
direction as well as when viewed from the front of the screen,
while improving the viewing angle dependence of the
.gamma.-characteristics by the pixel division method.
[0046] According to the second aspect of the present invention, the
independent gamma correction is carried out which shifts the
chromaticity when the screen is viewed from the front, from the
state maintaining the color balance toward blue in the vicinity of
the predetermined gradation value such that the gradation
dependence of the chromaticity is suppressed when viewed from the
oblique direction. Such an independent gamma correction reduces the
yellow tinge in the halftone caused by the color imbalance observed
in the oblique view in the conventional color liquid crystal
display device employing the pixel division method, and there is
obtained a situation in which the color balance is maintained
substantially for the almost whole gradation range in the oblique
view as well as in the front view (to the extent that matters
little for a human visual sense). As a result, it is possible to
display an image having a high color reproducibility when the
screen is viewed from an oblique direction as well as when viewed
from the front of the screen.
[0047] According to the third aspect of the present invention, the
independent gamma correction is carried out such that the gradation
dependence of the chromaticity is suppressed in the oblique view in
the vicinity of the predetermined gradation value, and also there
is obtained a situation in which the color balance in the front
view is maintained surely for the almost whole gradation values
except for the vicinity of the predetermined gradation value.
Accordingly, it is possible to display an image having a
sufficiently high color reproducibility for the almost whole
gradation range in the front view, while reducing the color
imbalance (specifically, the yellow tinge in the halftone) observed
in the oblique view in the conventional color liquid crystal
display device employing the pixel division method.
[0048] According to the fourth aspect of the present invention, the
independent gamma correction is carried out such that the gradation
dependence of the chromaticity is suppressed in the oblique view in
the vicinity of the predetermined gradation value, and also the
independent gamma correction is carried out such that the curve
representing the gradation dependence of the chromaticity in the
front view changes approximately monotonically with respect to the
gradation value. Accordingly, it is possible to make the
chromaticity shift by a change of the gradation value not to cause
a human sense of discomfort, while reducing the color imbalance
(specifically, the yellow tinge in the halftone) observed in the
oblique view in the conventional color liquid crystal display
device employing the pixel division method.
[0049] According to the fifth aspect of the present invention, by
correcting the gradation value indicated by the input signal with
reference to the correction table for the gamma correction
associating the gradation value before correction and the gradation
value after correction with each other for each of the primary
colors for color display, the gamma correction is carried out in
the same manner as in the first aspect of the present invention,
and thereby it is possible to display an image having a high color
reproducibility in the oblique view as well as in the front view.
Also, it is possible to adjust easily a correction amount in the
independent gamma correction, by changing the contents of the
correction table.
[0050] According to the sixth aspect of the present invention,
applying voltages which are different from each other and change in
a predetermined period and in a predetermined amplitude to the
first and second sub-pixel electrodes provides luminance values
different from each other to the sub-pixels in each of the pixel
formation portions, and also the independent gamma correction is
carried out such that the gradation dependence of the chromaticity
is suppressed in the oblique view in the vicinity of the
predetermined gradation value determined by the area ratio of the
first sub-pixel electrode to the second sub-pixel electrode and the
difference in the applied voltage between the first auxiliary
electrode and the second auxiliary electrode. Thereby, it is
possible to display an image having a high color reproducibility in
the oblique view as well as in the front view, while realizing the
pixel division method in a comparatively simple configuration to
improve the viewing angle dependence of the
.gamma.characteristics.
[0051] The seventh to tenth aspects of the present invention have
the same advantages as those of the first to the fourth aspects of
the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] FIG. 1 is a block diagram illustrating a whole configuration
of a color liquid crystal display device according to a first
embodiment of the present invention.
[0053] FIG. 2 is a schematic diagram illustrating a configuration
of a display part in the first embodiment
[0054] FIG. 3 consists of a schematic diagram (A) and an equivalent
circuit diagram (B) respectively illustrating an electrical
configuration of a pixel formation portion in the display part of
the first embodiment.
[0055] FIG. 4 consists of signal waveform charts (A to F) for
illustrating operation of the liquid crystal display device
according to the embodiment.
[0056] FIG. 5 is a characteristic diagram showing VT
characteristics (applied voltage-transmittance characteristics) in
a liquid crystal display device employing the pixel division
method.
[0057] FIG. 6 is a characteristic diagram showing an example of
.gamma.-characteristics.
[0058] FIG. 7 is a characteristic diagram showing different VT
characteristics for different colors of a pixel in the liquid
crystal display device.
[0059] FIG. 8 is a VT characteristic diagram for illustrating a
problem in association with color-reproducibility in the liquid
crystal display device employing the pixel division method.
[0060] FIG. 9 is a characteristic diagram for illustrating
gradation dependence of chromaticity in the liquid crystal display
device employing the pixel division method.
[0061] FIG. 10 consists of a characteristic diagram (A) and a
chromaticity diagram (B) respectively for illustrating a problem in
adjusting a color balance to obtain a good color tracking in the
liquid crystal display device employing the pixel division
method.
[0062] FIG. 11 consists of a characteristic diagram (A) and a
chromaticity diagram (B) respectively for illustrating an
independent gamma correction for obtaining the color tracking in
the first embodiment.
[0063] FIG. 12 is a characteristic diagram showing a state in which
a viewing angle dependence of the gamma characteristics changes
according to the amplitude of an auxiliary capacitance line voltage
in the liquid crystal display device employing the pixel division
method.
[0064] FIG. 13 is a characteristic diagram showing a state in which
the viewing angle dependence of the gamma characteristics changes
according to the pixel division ratio in the liquid crystal display
device employing the pixel division method.
[0065] FIG. 14 is a block diagram showing a configuration of a
display control circuit in the first embodiment.
[0066] FIG. 15 is a diagram for illustrating a correction table for
the independent gamma correction in the first embodiment.
[0067] FIG. 16 consists of a characteristic diagram (A) and a
chromaticity diagram (B) respectively for illustrating the
independent gamma correction for obtaining the color tracking in a
second embodiment of the present invention.
[0068] FIG. 17 consists of diagrams (A, B) for illustrating a
problem in association with the color tracking (gradation
dependence of the chromaticity) in the liquid crystal display
device employing the pixel division method.
DESCRIPTION OF THE REFERENCE SYMBOLS
[0069] 10 Pixel formation portion
[0070] 10a First sub-pixel formation portion
[0071] 10b Second sub-pixel formation portion
[0072] 12a First TFT (first thin film transistor)
[0073] 12b Second TFT (second thin film transistor)
[0074] 14a First sub-pixel electrode
[0075] 14b Second sub-pixel electrode
[0076] 16a First auxiliary electrode
[0077] 16b Second auxiliary electrode
[0078] 20 Gamma correction part
[0079] 23 Gamma-correction processing part
[0080] 21r R gamma-correction table
[0081] 21g G gamma-correction table
[0082] 21b B gamma-correction table
[0083] 200 Display control circuit
[0084] 300 Data-signal-line drive circuit
[0085] 400 Scanning-signal-line drive circuit
[0086] 500 Display part
[0087] Ccsa First auxiliary capacitance
[0088] Ccsb Second auxiliary capacitance
[0089] Ecom Common electrode
[0090] Vcs1 First auxiliary electrode voltage
[0091] Vcs2 Second auxiliary electrode voltage
[0092] Vcom Common electrode voltage
[0093] Vda First sub-pixel voltage
[0094] Vdb Second sub-pixel voltage
[0095] CS1 First auxiliary capacitance line
[0096] CS2 Second auxiliary capacitance line
[0097] G(i) Scanning signal line (i=1 to n)
[0098] S(j) Data signal line (j=1 to m)
[0099] Vg Gate signal voltage
[0100] Vs Data signal voltage
[0101] Lr, Lg, Lb Gradation signal (before correction)
[0102] Lmr, Lmg, Lmb Gradation signal (after correction)
[0103] IL Oblique hue correction range (oblique color imbalance
range)
BEST MODES FOR CARRYING OUT THE INVENTION
[0104] Hereinafter, embodiments of the present invention will be
described with reference to the accompanying drawings. The
following description assumes that a display part employs a
vertical alignment mode and is configured to provide a normally
black display. Here, a drive method thereof may be a line-inversion
drive method in which a voltage applied to liquid crystal is
inverted every frame period and also every one or a predetermined
number of scanning signal lines, or a dot-inversion drive method in
which the voltage applied to the liquid crystal is inverted every
frame period and also every scanning signal line and video signal
line.
1. First Embodiment
[0105] <1.1 Whole Configuration of a Liquid Crystal Display
Device>
[0106] FIG. 1 is a block diagram illustrating a whole configuration
of an active-matrix liquid crystal display device according to a
first embodiment of the present invention. This liquid crystal
display device is provided with: a display control circuit 200; a
pixel electrode drive circuit including a data-signal-line drive
circuit (also called "source driver") 300, a scanning-signal-line
drive circuit (also called "gate driver") 400, and a common
electrode drive circuit (not shown in the drawing); an auxiliary
electrode drive circuit 600; and a display part 500. The display
part 500 includes a plurality of (m) data signal lines S(1) to
S(m), a plurality of (n) scanning signal lines G(1) to G(n), and a
plurality of (m.times.n) pixel formation portions provided
correspondingly to respective intersections of the plurality of
data signal lines S(1) to S(m) and the plurality of scanning signal
lines G(1) to G(n). These pixel formation portions include three
kinds of pixel formation portions corresponding to the three
primary colors for displaying a color image, that is, an R pixel
formation portion forming an R (red) pixel, a G pixel formation
portion forming a G (green) pixel, and a B pixel formation portion
forming a B (blue) pixel. Three pixel formations 10 of R pixel
formation portion, G pixel formation portion and G pixel formation
portion, neighboring in a horizontal direction as shown in FIG. 2,
constitute one of units of display, which are arranged in a matrix
on the display part 500.
[0107] The present embodiment employs the pixel division method for
improving a viewing angle dependence of display characteristics,
and each pixel formation portion 10 in the display part 500 is
configured as shown in (A) and (B) of FIG. 3. Here, (A) of FIG. 3
is a schematic diagram showing an electrical configuration of one
pixel formation portion in the display part 500 and (B) of FIG. 3
is an equivalent circuit diagram showing the electrical
configuration in the pixel formation portion. As shown in these (A)
and (B) of FIG. 3, each pixel formation portion 10 includes a first
and a second sub-pixel formation portions 10a and 10b having
sub-pixel electrodes 14a and 14b independent from each other,
respectively, and an average of a luminance value of a sub-pixel
formed by the first sub-pixel formation portion 10a and a luminance
value of a sub-pixel formed by the second sub-pixel formation
portion 10b becomes a luminance value of a pixel formed by the
pixel formation portion 10.
[0108] In each of the pixel formation portion 10, the first
sub-pixel formation portion 10a includes a first TFT 12a, the gate
terminal of which is connected to a scanning signal line G(i)
passing through an intersection corresponding to the pixel
formation portion 10 and the source terminal of which is connected
to a data signal line S(j) passing through the intersection, a
first sub-pixel electrode 14a connected to the drain terminal of
the first TFT 12a, and a first auxiliary electrode 16a disposed so
as to form a first auxiliary capacitance Ccsa between the first
sub-pixel electrode 14a and the same. Also, the second sub-pixel
formation portion 10b includes a second TFT 12b, the gate terminal
of which is connected to the scanning signal line G(i) passing
through the intersection and the source terminal of which is
connected to the data signal line S(j) passing through the
intersection, a second sub-pixel electrode 14b connected to a drain
terminal of the second TFT 12b, and a second auxiliary electrode
16b disposed so as to form a second auxiliary capacitance Ccsb
between the second sub-pixel electrode 14b and the same. Further,
each of the pixel formation portion 10 includes a liquid crystal
layer as an electro-optical element provided commonly at all the
pixel formation portions 10 and sandwiched between a common
electrode Ecom provided commonly at all the pixel formation
portions 10 and the first and second sub-pixel electrodes. A first
liquid crystal capacitance Clca is formed by the first sub-pixel
electrode 14a, the common electrode Ecom and the liquid crystal
layer sandwiched therebetween, and a second liquid crystal
capacitance Clcb is formed by the second sub-pixel electrode 14b,
the common electrode Ecom and the liquid crystal layer sandwiched
therebetween. Hereinafter, a sum of the first liquid crystal
capacitance Clca and the first auxiliary capacitance Ccsa is
referred to as a "first sub-pixel capacitance" and designated by a
symbol "Cpa", and a sum of the second liquid crystal capacitance
Clcb and the second auxiliary capacitance Ccsb is referred to as a
"second sub-pixel capacitance" and designated by a symbol "Cpb".
Capacitance values of these capacitances Clca, Clcb, Ccsa, Ccsb,
Cpa and Cpb are also designated by the same symbols Clca, Clcb,
Ccsa, Ccsb, Cpa and Cpb.
[0109] As shown in (A) and (B) FIG. 3, in the display part 500
there are disposed a first auxiliary capacitance line CS1 and a
second auxiliary capacitance line CS2 in parallel to the scanning
signal line G(i) so as to sandwich each of the pixel formation
portion 10 in addition to the foregoing data signal lines S(1) to
S(m) and scanning signal lines G(1) to G(n), and the first
auxiliary capacitance line CS1 is disposed on one side of each
pixel formation portion 10 (upper side of (A) and (B) of FIG. 3)
and the second auxiliary capacitance line CS2 is disposed on the
other side of each pixel formation portion 10 (lower side of (A)
and (B) of FIG. 3). The first auxiliary capacitance line CS1 is
connected to the auxiliary electrode 16a of the first sub-pixel
formation portion 10a and the second auxiliary capacitance line CS2
is connected to the auxiliary electrode 16b of the second sub-pixel
formation portion 10b in each pixel formation portion 10.
Accordingly, the first sub-pixel electrode 14a is connected to the
data signal line S (j) via the first TFT 12a and also connected to
the first auxiliary capacitance line CS1 via the first auxiliary
capacitance Ccsa, and the second sub-pixel electrode 14b is
connected to the data signal line S (j) via the second TFT 12b and
also connected to the second auxiliary capacitance line CS2 via the
second auxiliary capacitance Ccsb.
[0110] As shown in FIG. 1, the display control circuit 200 receives
a data signal DAT and a timing control signal TS transmitted from
outside and outputs a digital image signal DV, a source start pulse
signal SSP, a source clock signal SCK, a latch strobe signal LS, a
gate start pulse signal GSP, a gate clock signal GCK, etc. The
digital image signal DV is a signal representing an image to be
displayed on the display part 500, and the source start pulse
signal SSP, source clock signal SCK, latch strobe signal LS, gate
start pulse signal GSP, gate clock signal GCK, etc. are timing
signals for controlling timings for displaying the image on the
display part 500.
[0111] The data-signal-line drive circuit 300 receives the digital
image signal DV, the source start pulse signal SSP, source clock
signal SCK and latch strobe signal LS outputted from the display
control circuit 200, and applies the data signal to each of the
data signal lines S (1) to S (m) for charging the first sub-pixel
capacitance Cpa (=Clca+Ccsa) and the second sub-pixel capacitance
Cpb (=Clcb+Ccsb) in each pixel formation portion 10 of the display
part 500. At this time, the data signal-line drive circuit 300
holds sequentially the digital image signal DV exhibiting voltages
to be applied to data signal lines S (1) to S (m), respectively, at
each timing when a pulse of the source clock signal SCK is
generated. Then, the held digital image signal DV is converted into
analog voltages at a timing when a pulse of the latch strobe signal
LS is generated, and the analog voltages are applied to all the
data signal lines S (1) to S (m), respectively as data signal
voltages, at the same time.
[0112] The scanning-signal-line drive circuit 400 applies active
scanning signals (scanning signal voltages Vg (=VgH) to switch on
the first TFT 12a and the second TFT 12b) sequentially to the
scanning signal lines G (1) to G (n) based on the gate start pulse
signal GSP and the gate clock signal GCK outputted from the display
control circuit 200.
[0113] The auxiliary electrode drive circuit 600 generates a first
auxiliary electrode voltage Vcs1 and a second auxiliary electrode
voltage Vcs2 based on the timing signal provided from the display
control circuit 200, and applies these voltages Vcs1 and Vcs2 to
the first auxiliary capacitance line CS1 and the second auxiliary
capacitance line CS2 of the display part 500, respectively.
[0114] The common electrode drive circuit (not shown in the
drawing) applies a predetermined voltage to the common electrode
Ecom as a common electrode voltage Vcom. In the present embodiment,
the common electrode voltage Vcom is assumed to be a fixed
voltage.
[0115] <1.2 Operation of the Liquid Crystal Display
Device>
[0116] Operation of the liquid crystal display device configured as
described above according to the present embodiment will be
described with reference to signal waveform charts shown in FIG.
4.
[0117] Now attention is focused on the pixel formation portion 10
composed of the first sub-pixel formation portion 10a and the
second sub-pixel formation portion 10b shown in (A) and (B) of FIG.
3. A data signal voltage Vs as shown in (A) of FIG. 4 is applied to
the data signal line corresponding to this pixel formation portion
10 (hereinbelow, referred to as "corresponding data signal line") S
(j), and the scanning signal voltage Vg as shown in (B) of FIG. 4
is applied to the scanning signal line corresponding to this pixel
formation portion 10 (hereinbelow, referred to as "corresponding
scanning signal line") G (i). Meanwhile, to the first auxiliary
capacitance line CS1 is applied a periodically varying voltage
having a rectangular waveform with an amplitude of Vcs as shown in
(C) of FIG. 4, as a first auxiliary electrode voltage Vcs1, and to
the second auxiliary capacitance line CS2 is applied a periodically
varying voltage having a rectangular waveform with the amplitude of
Vcs as shown in (D) of FIG. 4 as a second auxiliary electrode
voltage Vcs2. Here, the first auxiliary electrode voltage Vcs1 and
the second auxiliary electrode voltage Vcs2 have the same amplitude
and phases different from each other by 180 degrees.
[0118] When the data signal voltage Vs, scanning signal voltage Vg,
and the first and second auxiliary electrode voltages Vcs1 and Vcs2
described above are applied by the data-signal-line drive circuit
300, scanning-signal-line drive circuit 400 and auxiliary electrode
drive circuit 600, a voltage of the first sub-pixel electrode 14a
(hereinbelow, referred to as "first sub-pixel voltage") Vda and a
voltage of the second sub-pixel electrode 14b (hereinbelow,
referred to as "second sub-pixel voltage") Vdb change as follows.
That is, when the scanning signal voltage Vg changes from an off
voltage VgL to an on voltage VgH (corresponding scanning signal
line G (i) is selected), the first TFT T12a and the second TFT 12b
are changed from an off state to an on state, and the data signal
voltage Vs (voltage of positive polarity with reference to the
common electrode voltage Vcom) at this timing is applied to the
first sub-pixel electrode 14a via the first TFT 12a and the second
sub-pixel electrode 14b via the second TFT 12b. Thereby, both of
the first and second sub-pixel voltages Vda and Vdb become equal to
the data signal voltage Vs. Then, when the scanning signal voltage
Vg changes to the off voltage VgL (corresponding scanning signal
line G (i) becomes a non-selected state), both of the first TFT 12a
and the second TFT 12b are changed from the on state to the off
state. At this time, the change of the scanning signal voltage Vg
(VgH to VgL) provides an effect to the first and second sub-pixel
voltages Vda and Vdb and reduces these voltages Vda and Vdb via
parasitic capacitances Cgd between the gates and the drains of the
first and second TFTs 12a and 12b. This phenomenon is called a
"pull-in phenomenon" and a voltage reduction in this case .DELTA.V
is called a "pull-in voltage" (.DELTA.V>0).
[0119] Subsequently, the first auxiliary electrode voltage Vcs1 is
increased by the amplitude of Vcs and the second auxiliary
electrode voltage Vcs2 is decreased by the amplitude of Vcs ((C)
and (D) of FIG. 4). Then, the first and second auxiliary electrode
voltages Vcs1 and Vcs2 repeat alternately the increase and decrease
by the amplitude Vcs in the predetermined period until the scanning
signal voltage Vg is changed next to the on voltage VgH (until the
corresponding scanning signal line G (i) is selected). Note that
the first and second auxiliary electrode voltages Vcs1 and Vcs2
have phases different from each other by 180 degrees. While the
scanning signal line voltage Vg is the off voltage (while the
corresponding scanning signal line G (i) is in the non-selected
state and the first and second TFTs 12a and 12b are in the off
state), the first sub-pixel voltage Vda is affected by the periodic
change of the first auxiliary electrode voltage Vcs1 via the first
auxiliary capacitance Ccsa and changes as shown in (E) of FIG. 4,
and the second sub-pixel voltage Vdb is affected by the periodic
change of the second auxiliary electrode voltage Vcs2 via the
second auxiliary capacitance Ccsb and changes as shown in (F) of
FIG. 4.
[0120] When the scanning signal line voltage Vg is changed next to
the on voltage VgH, the data signal voltage Vs (voltage of negative
polarity with reference to the common electrode voltage Vcom) at
this timing is applied to the first sub-pixel electrode 14a via the
first TFT 12a and the second sub-pixel electrode 14b via the second
TFT 12b. Then, when the scanning signal voltage Vg is changed to
the off voltage VgL, both of the first TFT 12a and the second TFT
12b go into the off state. At this time, by the pull-in phenomenon
caused by the parasitic capacitances Cgd between the gates and
drains of the first and second TFTs 12a and 12b, the first and
second sub-pixel voltages Vda and Vdb, which are voltages of
negative polarity, are reduced by about .DELTA.V (.DELTA.V>0).
After that, in the same manner as above, the first and second
auxiliary electrode voltages Vcs1 and Vcs2 repeat alternately the
increase and decrease by the amplitude Vcs in the predetermined
period until the scanning signal voltage Vg is changed next to the
on voltage VgH. Thereby, the first sub-pixel voltage Vda is
affected by the periodic change of the first auxiliary electrode
voltage Vcs1 via the first auxiliary capacitance Ccsa and changes
as shown in (E) of FIG. 4, and the second sub-pixel voltage Vdb is
affected by the periodic change of the second auxiliary electrode
voltage Vcs2 via the second auxiliary capacitance Ccsb and changes
as shown in (F) of FIG. 4.
[0121] Here, when the data signal line voltage Vs is designated by
Vsp in the positive polarity and designated by Vsn in the negative
polarity, an effective value Vlca_rms of an applied voltage to the
liquid crystal (hereinbelow referred to as a "first sub-pixel
liquid crystal voltage") in the first sub-pixel formation portion
10a is provided as follows according to (E) of FIG. 4,
Vlca.sub.--rms=Vsp-.DELTA.V+(1/2)Vcs(Ccsa/Cpa)-Vcom (1),
and an effective value Vlcb_rms of an applied voltage to the liquid
crystal (hereinbelow referred to as a "second sub-pixel liquid
crystal voltage") in the second sub-pixel formation portion 10b is
provided as follows according to (F) of FIG. 4,
Vlcb.sub.--rms=Vsp-.DELTA.V-(1/2)Vcs(Ccsb/Cpb)-Vcom (2).
From the equations (1) and (2), the effective value of the first
sub-pixel liquid crystal voltage Vlca_rms is larger than that of
the second sub-pixel liquid crystal voltage Vlcb_rms. Further, when
the first and second liquid crystal capacitances Clca and Clcb are
assumed to be approximately the same as each other and also the
first and second auxiliary capacitances Ccsa and Ccsb are assumed
to be the same as each other (Clca=Clcb and Ccsa=Ccsb), and thereby
Cp=Cpa=Cpb is assumed, a difference between the effective value of
the first sub-pixel liquid crystal voltage Vlca_rms and the
effective value of the second sub-pixel liquid crystal voltage
Vlcb_rms, .DELTA.Vlc=Vlca_rms-Vlcb_rms, becomes
.DELTA.Vlc=Vcs(Ccs/Cp) (3).
Therefore, the difference .DELTA.Vlc between the effective value of
the first sub-pixel liquid crystal voltage Vlca_rms and the
effective value of the second sub-pixel liquid crystal voltage
Vlcb_rms is proportional to the amplitude of the auxiliary
electrode voltage Vcs and can be controlled by this amplitude
Vcs.
[0122] In the pixel division method described above, the effective
value of the first sub-pixel liquid crystal voltage Vlca_rms
becomes higher and the effective value of the second sub-pixel
liquid crystal voltage Vlcb_rms becomes lower than an apparent
applied-voltage onto the liquid crystal in the pixel formation
portion 10, Vlc_ap=Vsp-.DELTA.V-Vcom. Therefore, a relationship
between the apparent applied voltage V=Vlc_ap and transmittance T
(VT characteristics) becomes as shown in FIG. 5. That is, the VT
characteristics of the first sub-pixel formation portion 10a
becomes as shown by a characteristic curve VTa and the VT
characteristics of the second sub-pixel formation portion 10b
becomes as shown by a characteristic curve VTb. Further, the VT
characteristics of the pixel formation portion 10 become average
characteristics provided by these VT characteristics curves VTa and
VTb, that is, characteristics as shown by a dotted line in FIG.
5.
[0123] In the present embodiment, when voltages according to the
data signal DAT (gradation values thereof), which is the input
signal from outside, are applied to the liquid crystal in the first
and second sub-pixel formation portions 10a and 10b, the light
transmittance is controlled according to the above described VT
characteristics in each of the pixel formation portions 10 of the
display part 500, and thereby an image exhibited by the data signal
DAT of the input signal is displayed. Further, by employing the
pixel division method as described above, the viewing angle
dependence of the .gamma.-characteristics is improved in the liquid
crystal display device.
[0124] <1.3 Color Tracking and Independent Gamma
Correction>
[0125] A video signal such as a television signal or the like
assumes the .gamma.-characteristics of a CRT (Cathode Ray Tube)
display device, that is, .gamma.-characteristics as shown in FIG.
6. Accordingly, to reproduce (display) an image having a good
gradation from such a video signal in the liquid crystal display
device, a gradation value or the like indicated by the input signal
needs to be corrected according to the VT characteristics of the
liquid crystal display device (refer to, e.g., FIG. 5), such that
the relationship between the gradation value indicated by the input
video signal and a luminance value of an image to be displayed,
that is, .gamma.-characteristics of the liquid crystal display
device becomes the .gamma.-characteristics as shown in FIG. 6. Such
gamma correction methods include a method to correct a gradation
value indicated by the input signal using a lookup table as a
correction table, and a method to adjust a voltage division ratio
in a voltage division circuit (gradation voltage generation
circuit) for generating a gradation voltage to be used in
generation of the data signal voltage Vs (refer to, e.g., Japanese
Unexamined Patent Application Publication No. 2002-258813 (patent
reference 1) and Japanese Unexamined Patent Application Publication
No. 2001-222264 (patent reference 2)).
[0126] The display part of the color liquid crystal display device
includes three kinds of the pixel formation portions, R, G, and B
pixel formation portions, as shown in FIG. 2. Generally, the VT
characteristics (applied voltage-transmittance characteristics) of
the color liquid crystal display device are different slightly
among these three kinds of the pixel formation portions as shown in
FIG. 7. Therefore, in a case without the independent gamma
correction, when a video signal exhibiting achromatic gradation
values (monochrome signal) is inputted to the color liquid crystal
display device and the gradation value of the monochrome signal is
changed, the chromaticity of the displayed image changes
considerably against the gradation as shown in FIG. 9 (hereinbelow,
a curve representing a gradation dependence of the chromaticity of
a displayed image obtained when a video signal exhibiting such
achromatic gradation values is inputted is referred to as a "color
tracking curve"). Here, x and y of vertical axes in FIG. 9 are x-y
coordinates in the XYZ colorimetric system introduced by the CIE
(Commission Internationale de l'Eclarirange) (same in FIG. 10, FIG.
11, and FIG. 16 to be referred to hereinbelow).
[0127] This FIG. 9 shows that the chromaticity changes toward blue
as a gradation value is reduced from 255 in a displayed image of
the color liquid crystal display device. In this manner, the
chromaticity changes considerably and satisfactory chromaticity
characteristics are not obtained, although a video signal
exhibiting achromatic gradation values is inputted.
[0128] Accordingly the independent gamma correction is carried out
such that the color balance in the front-view does not change
against the gradation, and thereby flat chromaticity
characteristics are obtained against the gradation as shown in (A)
of FIG. 10. In an example shown in (A) of FIG. 10, gradation values
of 0 to 255 are allotted to each R, G, and B (gradation display
with eight bits each).
[0129] Note that, in the present embodiment, the chromaticity
characteristics are adjusted to become flat in a gradation range of
32 to 255. This is because there is a limit to a range where the
chromaticity can be corrected by the R, G, and B independent gamma
correction of the liquid crystal while suppressing a black
luminance, since the chromaticity in a gradation near black is
determined by a light leak in polarizer plates in the cross-nicol
state and a color filter (CF). Accordingly, in the present
embodiment, the R, G, and B independent gamma correction is carried
out such that the chromaticity comes gradually close to the
chromaticity of black (zero gradation value) in a range below a
gradation value of 32 as shown in (A) of FIG. 10. Thereby, the
color balance can be maintained in the gradation value range of 32
to 255, when the screen of the liquid crystal display device is
viewed from the front (in the front view).
[0130] In the color liquid crystal display device employing the
pixel division method such as the present embodiment, a luminance
value of a pixel (any of R, G, and B pixels) formed by each pixel
formation portion 10 is determined by a transmittance value based
on the average characteristic curve (characteristic curve shown by
a dotted line in FIG. 8) of the characteristic curves VTa and VTb
which represent the VT characteristics of the first and second
sub-pixel formation portions 10a and 10b composing the pixel
formation portion 10 as shown in FIG. 8. That is, light flux of
each pixel formation portion 10 is a sum of a light flux of the
first sub-pixel formation portion 10a and a light flux of the
second sub-pixel formation portion 10b which are determined by the
transmittance values based on the above described two
characteristic curves VTa and VTb, respectively. Therefore, in the
pixel division method, blue transmittance decreases and the color
balance breaks in two voltage ranges IVa and IVb as shown in FIG.
8, since the blue transmittance decreases at some gradient values
as shown in FIG. 7.
[0131] As described hereinabove, the retardation of the liquid
crystal has a wavelength dependence and thereby VT characteristics
are different among the three kinds of pixels R, G, and B and these
differences are larger when a screen is viewed from the oblique
direction (in the oblique view) than when viewed from the front (in
the front view). Therefore, as shown in (A) of FIG. 10, even when a
flat color tracking curve is obtained in the front view (in the
gradation range of 32 to 255), a color imbalance range IL appears
in the halftone in the oblique view. That is, when a video signal
exhibiting the achromatic gradation values is inputted and the
gradation value is changed from 0 to 255, a trajectory on the
chromaticity diagram in the front view is obtained as shown by a
solid line in (B) of FIG. 10 and a trajectory in the oblique view
is obtained as shown by a dotted line in (B) of FIG. 10. This means
that there is caused the yellow tinge in the color imbalance range
IL of the halftone in the oblique view (refer to (B) of FIG.
17).
[0132] Accordingly, in the present embodiment, the independent
gamma correction is carried out such that chromaticity coordinate
values x and y, which represent a chromaticity in the front view in
the color imbalance range IL of the halftone, become slightly
smaller than those of the state maintaining the color balance as
shown in (A) of FIG. 11, when the video signal exhibiting the
achromatic gradation values is input and the gradation value is
changed. Thereby, in a color tracking curve in the oblique view, as
shown in (A) of FIG. 11, the chromaticity coordinate values x and y
are suppressed from increasing from those of the state maintaining
the color balance in the color imbalance range IL. Note that the
color balance is maintained in the gradation value range of 32 to
255 except for the color imbalance range IL. That is, the color
tracking curve representing the gradation dependence of the
chromaticity is flat in that range.
[0133] In such an independent gamma correction, the color tracking
curve in the front view corresponds to a trajectory on the
chromaticity diagram shown by a solid line in (B) of FIG. 11, and
the color tracking curve in the oblique view corresponds to a
trajectory on the chromaticity diagram shown by a dotted line in
(B) of FIG. 11. As apparent from these trajectories, in the
independent gamma correction of the present embodiment, the
chromaticity in the front view is shifted toward blue in the color
imbalance range IL of the halftone, and thereby the yellow tinge in
the oblique view can be reduced. Here, the shift amount toward blue
in the front view in the color imbalance range IL (reduced amounts
of the chromaticity coordinates x and y) is determined such that
the blue tinge does matter little for a human visual sense in the
front view and also the yellow tinge does matter little for the
human visual sense in the oblique view (hereinbelow, such color
balance adjustment is referred to as "oblique color imbalance
correction"). Note that, here, an angle (acute angle) formed by the
normal line of a screen and a visual axis of a screen viewer is
referred to as a "viewing angle". In the present embodiment,
viewing the screen from an oblique direction of 45 degrees (a
viewing angle of 45 degrees) is referred to as "the oblique view",
but viewing the screen from an oblique direction of another angle,
for example, 60 degrees may also be referred to as "the oblique
view".
[0134] To carry out the independent gamma correction for obtaining
the color tracking curve as described above ((A) of FIG. 11) in the
present embodiment, it is necessary to specify the color imbalance
range IL of the halftone as a range where the oblique color
imbalance correction is carried out (hereinbelow, this range is
referred to as an "oblique hue correction range). This oblique hue
correction range IL appears due to employment of the, pixel
division method, and a position thereof (gradation value breaking
the color balance) depends on the pixel division ratio and the
difference in the effective value of the liquid crystal voltage
.DELTA.Vlc=Vcs (Ccs/Cp) between the effective value of the first
sub-pixel liquid crystal voltage Vlca_rms and the effective value
of the second sub-pixel liquid crystal voltage Vlcb_rms. That is,
in the present embodiment, the position depends on the area ratio
of the first sub-pixel electrode 14a to the second sub-pixel
electrode 14b in each pixel formation portion 10 and the amplitude
Vcs of the first and second auxiliary electrode voltages Vcs1 and
Vcs2. Hereinbelow, this point will be described with reference to
FIGS. 12 and 13.
[0135] FIG. 12 is a characteristic diagram showing how the viewing
angle dependence of the .gamma.-characteristics changes according
to the amplitude of the auxiliary capacitance line voltage in the
liquid crystal display device employing the pixel division method.
Specifically, this characteristic diagram shows a relationship
between a gradation value in the front view (hereinbelow, referred
to as "front gradation") and a gradation value in the oblique view
(hereinbelow, referred to as "oblique gradation"), when an image
with the gradation is displayed on the screen. A curve representing
this relationship is referred to as a "viewing angle dependence
curve" and the horizontal axis thereof represents the front
gradation calculated from
255.times.(front viewing angle normalized transmittance ratio/100)
(1/2.2) (4),
and the vertical axis thereof represents the oblique gradation
calculated from
255.times.(right 45 degree front viewing angle normalized
transmittance ratio/100) (1/2.2) (5).
Also, FIG. 12 shows a straight bold line with a gradient of 1 as a
reference line VAO, and, as the viewing angle dependence curves
come closer to this reference line VAO, a difference between the
front gradation and the oblique gradation becomes smaller and the
viewing angle dependence of the .gamma.-characteristics becomes
smaller. In a case where the display part 500 employs the vertical
alignment mode and is configured to have the normally black
display, the .gamma.-characteristics are different between in the
front view and in the oblique view, and an image becomes to show so
called "white floating" in the oblique view, which is not observed
in the front view. However, by the configuration in which each
pixel is composed of a relatively bright sub-pixel and a relatively
dark sub-pixel, that is, by employment of the pixel division
method, the "white floating" in the oblique view is reduced and the
viewing angle dependence is improved.
[0136] FIG. 12 shows four viewing angle dependence curves in a case
where the pixel division ratio is 1:1, that is, in a case where an
area ratio of the first sub-pixel electrode 14a to the second
sub-pixel electrode 14b is 1:1. A solid line shows a viewing angle
dependence curve when the amplitude of the first and second
auxiliary electrode voltages Vcs1 and Vcs2 (hereinbelow, referred
to as "CS amplitude") Vcs is zero volt, a dotted line shows a
viewing angle dependence curve when the CS amplitude Vcs is 1.5 V,
a dashed-dotted line shows a viewing angle dependence curve when
the CS amplitude Vcs is 3.5 V, and a broken line shows a viewing
angle dependence curve when the CS amplitude Vcs is 5.5 V.
[0137] As shown in FIG. 12, in the viewing angle dependence curve,
a bending curvature at a bending part (corresponding to an
inflection point) shown by a circle becomes larger and the bending
part shifts in a direction indicated by an arrow when the CS
amplitude Vcs is changed from 1.5 V to 5.5 V. In the oblique view,
the color balance is broken in such a bending part and the yellow
tinge is caused ((B) of FIG. 17). That is, the color imbalance
range in the oblique view shifts by the CS amplitude Vcs as shown
by a shift of the circle in FIG. 12. Accordingly, to obtain the
color tracking curve as shown in FIG. 11, it is necessary to carry
out the independent gamma correction according to the CS amplitude
Vcs. Here, to carry out the independent gamma correction according
to the CS amplitude Vcs using the foregoing equation (3) means to
carry out the independent gamma correction according to a
difference between the applied voltages on the liquid crystal in
the first and second sub-pixel formation portions 10a and 10b.
[0138] FIG. 13 is a characteristic diagram showing how the viewing
angle dependence of the .gamma.-characteristics is changed by the
pixel division ratio in the liquid crystal display device employing
the pixel division method and shows a relationship between the
front gradation value and the oblique gradation value (viewing
angle dependence curve) calculated in the same manner as in FIG. 12
for different pixel division ratios. That is, FIG. 13 shows three
viewing angle dependence curves in a case where the CS amplitude
Vcs is 3.5 V. A solid line shows the viewing angle dependence curve
when the pixel division ratio, more specifically, an area ratio of
one sub-pixel electrode whose luminance is higher of the first and
second sub-pixel electrodes 14a and 14b to the other sub-pixel
electrode whose luminance is lower (bright sub-pixel area to dark
sub-pixel area) is 1:1, a dotted line shows a viewing angle
dependence curve when the ratio of the bright sub-pixel area to the
dark sub-pixel area is 1:2, and a dashed and dotted line shows a
viewing angle dependence curve when a ratio of the bright sub-pixel
area to the dark sub-pixel area is 1:3.
[0139] As shown in FIG. 13, in the viewing angle dependence curve,
a gradation value providing the bending part (part corresponding to
an inflection point) pointed by an arrow shifts to the lower
gradation side when the pixel division ratio (ratio of the bright
sub-pixel area to the dark sub-pixel area) is changed from 1:1 to
1:3, that is, when a ratio of the dark sub-pixel area is made
larger. In the oblique view, the color balance is broken in such a
bending part and the yellow tinge (FIG. 17) is caused. That is, the
color imbalance range in the oblique view changes according to the
pixel division ratio as shown by the arrows in FIG. 13.
Accordingly, to obtain the color tracking curve as shown in FIG.
11, it is necessary to carry out the independent gamma correction
according to the pixel division ratio.
[0140] As described above, the position (gradation value) where the
color imbalance range appears in the oblique view depends on the
pixel division ratio and the CS amplitude Vcs. Accordingly, in the
present embodiment, the oblique color imbalance correction is
carried out for the oblique color imbalance range determined by the
pixel division ratio and the CS amplitude Vcs so as to obtain the
color tracking curve as shown in FIG. 11. For example, in a case of
the viewing angle dependence characteristics shown in FIG. 13 (CS
amplitude Vcs is 3.5 V), the oblique color imbalance correction is
carried out for a vicinity of a gradation value of 130 when the
pixel division ratio is 1:1, for a vicinity of a gradation value of
100 when the pixel division ratio is 1:2, and for a vicinity of a
gradation value of 90 when the pixel division ratio is 1:3.
[0141] Next, there will be described a configuration for carrying
out the independent gamma correction in the present embodiment to
adjust the color balance including the oblique color imbalance
correction described above.
[0142] FIG. 14 is a block diagram showing a configuration of the
display control circuit 200 in the present embodiment. This display
control circuit 200 includes a gamma correction part 20 and a
timing control part 25. The data signal DAT is provided from
outside to the gamma correction part 20, and the timing control
signal TS is provided from outside to the timing control part
25.
[0143] The timing control part 25 generates the foregoing source
start pulse signal SSP, source clock signal SCK, latch strobe
signal LS, gate start pulse signal GSP, gate clock signal GCK, etc
based on the timing control signal TS.
[0144] The gamma correction part 20 includes a gamma correction
processing part 23, an R correction table 21r, a G correction table
21g, and a B correction table 21b and, with reference to these
correction tables 21r, 21g, and 21b, corrects a relationship
between a gradation value indicated by the data signal DAT from
outside and a luminance value of a pixel formed by the pixel
formation portion 10 according to the gradation value independently
for each of the primary colors (red, green, and blue). That is, the
data signal DAT, which is received by the gamma correction part 20,
is composed of an R gradation signal Lr exhibiting an R (red)
gradation value, a G gradation signal Lg exhibiting a G (green)
gradation value, and a B gradation signal Lb exhibiting a B (blue)
gradation value in an image to be displayed. The gamma correction
part 20 carries out an independent gamma correction, which is a
combination of the conventional correction (FIG. 10) for
maintaining the color balance in the almost whole gradation range
(gradation value range of 32 to 255 ) and the oblique color
imbalance correction according to the pixel division ratio and the
CS amplitude Vcs, for the R, G, and B gradation signals Lr, Lg, and
Lb so as to obtain the color tracking as shown in (A) of FIG.
11.
[0145] The R correction table 21r is a lookup table associating an
R gradation value before gamma correction with an R gradation value
after gamma correction, the G correction table 21g is a lookup
table associating a G gradation value before gamma correction with
a G gradation value after gamma correction, and B correction table
21b is a lookup table associating a B gradation value before gamma
correction with a B gradation value after gamma correction.
[0146] The gamma correction processing part 23 carries out the
independent gamma correction as shown in FIG. 15, for example, on
the data signal DAT composed of the R gradation signal Lr, G
gradation signal Lg, and B gradation signal Lb, using these R, G,
and B correction tables 21r, 21g, and 21b, and outputs a digital
image signal DV composed of an R gradation signal Lmr, G gradation
signal Lmg, and a B gradation signal Lmb after the correction. That
is, the gamma correction processing part 23 determines an R
gradation value after the gamma correction from a gradation value
before the gamma correction, that is, an R gradation value
indicated by the R gradation signal Lr from outside, by referring
to the R correction table 21r, and outputs a signal exhibiting the
R gradation value after the gamma correction as the corrected R
gradation signal Lmr. Also, the gamma correction processing part 23
determines a G gradation value after the gamma correction from a
gradation value before the gamma correction, that is, a G gradation
value indicated by the G gradation signal Lg from outside, by
referring to the G correction table 21g, and outputs a signal
exhibiting the G gradation value after the gamma correction as the
corrected G gradation signal Lmg. Further, the gamma correction
processing part 23 determines a B gradation value after the gamma
correction from a gradation value before the gamma correction, that
is, a B gradation value indicated by the B gradation signal Lb from
outside, by referring to the B correction table 21b, and outputs a
signal exhibiting the B gradation value after the gamma correction
as the corrected B gradation signal Lmb.
[0147] The digital image signal DV composed of the corrected R
gradation signal Lmr, corrected G gradation signal Lmg, and
corrected B gradation signal Lmb outputted in this manner is a
signal accommodating the color tracking as shown in (A) of FIG. 11
and provided to the data-signal-line drive circuit 300 as described
hereinabove. Thereby, the display part 500 displays a color image
exhibited by this digital image signal DV.
[0148] <1.4 Generation Method of Data for the Correction
Table>
[0149] As described above, the independent gamma correction is
carried out such that the color tracking shown (A) of FIG. 11 is
obtained, and, this gamma correction refers to the R, G, and B
correction tables 21r, 21g, and 21b. Accordingly, it is necessary
to generate data corresponding to such an independent gamma
correction for the R, G, and B correction table 21r, 21g, and 21b.
Such data for the R, G, and B correction table 21r, 21g, and 21b
(hereinbelow, referred to as "correction data") can be generated by
the following steps, for example. [0150] (1) First, generate the
correction data for carrying out the independent gamma correction
so as to suppress the gradation dependence of the chromaticity when
the screen is viewed from the front, that is, to obtain the color
tracking curve in the front view as shown in (A) of FIG. 10. [0151]
(2) Next, carry out a chromaticity measurement from directions of
45 degrees on the right and left side, while carrying out the
independent gamma correction based on the correction data. [0152]
(3) Adjust the correction data so as to suppress the gradation
dependence of the chromaticity in the oblique view (specifically,
the yellow tinge) in the oblique hue correction range of the
halftone according to a result of the chromaticity measurement.
That is, adjust the correction data so as to shift the chromaticity
in the front view from the state maintaining the color balance
toward blue in the oblique hue correction range in order to reduce
the yellow tinge in the oblique view in the halftone.
[0153] The color tracking shown in (A) of FIG. 11 is obtained by
the independent gamma correction based on the correction data after
the adjustment generated as described above. Accordingly, this
correction data after the adjustment may be used for the data of
the R, G, and B correction tables 21r, 21g, and 21b. Here, the
method for generating the correction data described above is an
example, and another method may be used for generating the
correction data if the correction data is generated such that color
tracking shown in (A) of FIG. 11 is obtained.
[0154] <1.5 Advantages>
[0155] In the present embodiment as described above, the
independent gamma correction is carried out such that the values of
the chromaticity coordinates, x and y, in the front view is reduced
slightly from the values in the state maintaining the color balance
in the oblique hue correction range in the halftone (color
imbalance range) IL (the chromaticity in the front view is shifted
toward blue), as shown in (A) of FIG. 11. Thereby, the values of
the chromaticity coordinates, x and y, in the oblique view is
suppressed from increasing above the values in the state
maintaining the color balance in the oblique hue correction range
IL (the shift of the chromaticity in the oblique view toward yellow
is reduced). By such oblique color imbalance correction, the color
imbalance of the halftone observed in the conventional color liquid
crystal display device employing the pixel division method is
suppressed to such an extent that matters little for a human visual
sense even in the oblique view, and the color balance comes to be
maintained substantially (to such an extent that matters little for
a human visual sense) for the almost whole gradation range
(gradation values of 32 to 255 ) in the oblique view as well as in
the front view. As a result, it is possible to realize a display
having high color reproducibility when the screen is viewed from
the oblique direction as well as from the front direction, while
improving the viewing angle dependence of the
.gamma.-characteristics by the pixel division method.
2. Second Embodiment
[0156] In the first embodiment, the chromaticity in the front view
in the oblique hue correction range (color imbalance range) IL of
the halftone is shifted toward blue, and thereby the shift of the
chromaticity toward yellow in the oblique view is reduced in the
oblique hue correction range IL and the color reproducibility in
the oblique view is improved. However, as shown in (A) of FIG. 11,
when the gradation value is reduced from 255 to 0, a shift amount
of the chromaticity from the state maintaining the color balance is
switched from increase to decrease at a predetermined gradation
value in the halftone. That is, while the chromaticity shifts
toward blue (negative direction) along with a reduction in the
gradation value in the range of the gradation values larger than
the predetermined gradation value, the chromaticity shifts toward
yellow (positive direction) along with a reduction in the gradation
value in the range of gradation values smaller than the
predetermined gradation value. This means that the color tracking
curve has a local minimum point at the predetermined gradation
value. Such an extremal point of the color tracking curve in the
halftone makes a viewer to feel an unnatural chromaticity
change.
[0157] Accordingly, in a color liquid crystal display device
according to a second embodiment of the present invention, the
independent gamma correction is carried out so as not to cause such
an unnatural chromaticity change. Hereinbelow, there will be
described a liquid crystal display device according to such present
embodiment. Here, a configuration of the present embodiment is the
same as that of the first embodiment except for an configuration of
R, G, and B gamma correction tables and part of a configuration in
a display part 500 (details to be described below), and therefore
the same part or a corresponding part is designated by the same
reference symbol and detailed description thereof will be
omitted.
[0158] The R, G, and B gamma correction tables 21r, 21g, and 21b in
the present embodiment are determined such that the independent
gamma correction is carried out by a gamma correction processing
part 23 for obtaining a color tracking in the front view as shown
by curves of a bold solid line and dotted line in (A) of FIG. 16
(refer to FIG. 14). Here, curves of a fine solid line and dotted
line represent the color tracking in the front view in the
foregoing first embodiment in (A) of FIG. 16 (refer to (A) of FIG.
11).
[0159] In the present embodiment, the independent gamma correction
is carried out by the gamma correction processing part 23 as
described below with reference to the R, G, and B
.gamma.-correction tables 21r, 21g, and 21b.
[0160] An oblique hue correction range IL shown in (A) of FIG. 16
is the same as the oblique hue correction range IL in the first
embodiment and determined by the pixel division ratio and the CS
amplitude Vcs (refer to FIG. 12 and FIG. 13). In the present
embodiment, the independent gamma correction is carried out such
that chromaticity (values of the chromaticity coordinates x and y)
in the front view in this oblique hue correction range IL becomes
the same as the extremal value in the chromaticity of the color
tracking curve at the gradation value where the chromaticity of the
color tracking curve in the front view in the first embodiment
becomes minimum (a gradation value approximately at the center of
the oblique hue correction range IL) Le, and such that the
chromaticity (values of the chromaticity coordinates x, and y)
changes monotonically along with a change of the gradation value
L.
[0161] For carrying out such independent gamma correction,
correction data (data to be set in the R, G, and B correction
tables 21r, 21g, and 21b ) can be generated as follows, for
example. That is, the correction data obtained by the foregoing
generation method in the first embodiment (correction data
corresponding to the color tracking in the first embodiment shown
by the curves of a fine solid line and dotted line in (A) of FIG.
16) may be adjusted such that a color tracking curve in the front
view changes monotonically as shown by the curves of a bold solid
line and dotted line. Note that this correction data generation
method is an example and the correction data may be generated by
another method if the correction data is generated such that the
color tracking as shown in (A) of FIG. 16 is obtained.
[0162] Here, as shown in (A) of FIG. 16, the present embodiment
employs a color filter or a polarizer plate having a black
chromaticity shifted toward blue in a display part 500 so as to
change the color tracking curve monotonically even in a gradation
value range of 0 to 32. As shown in (B) of FIG. 16, a position of
black (zero gradation value) B2 (0) of the present embodiment in
the chromaticity diagram is slightly different from a position of
black B1 (0) in the first embodiment or a conventional example.
Here, a color filter or a polarizer the same as conventional ones
may be used replacing such color filter or polarizer plate.
[0163] In the present embodiment as described above, the
chromaticity in the front view is shifted toward blue to the same
extent as in the first embodiment in the oblique hue correction
range (color imbalance range) IL in the halftone, and thereby the
shift toward yellow in the halftone is suppressed in the oblique
view as in the first embodiment and the color reproducibility is
improved. Further, the color tracking curve in the front view
changes monotonically and thereby the chromaticity shift by the
gradation value becomes not to provide a sense of discomfort to a
viewer differently from the case in the first embodiment.
3. Variation
[0164] In the first and second embodiments, the independent gamma
correction based on the correction tables 21r, 21g, and 21b
provides an appropriate color tracking and realizes a display
having a high color reproducibility in the oblique view as well as
in the front view. However, a method of such independent gamma
correction for improving the color reproducibility is not limited
to a method to correct the gradation signal Lr, Lg, or Lb according
to the correction table, but may be any method to correct a
relationship between a gradation value indicated by the signal
inputted in the liquid crystal display device as a signal
representing an image to be displayed-and a luminance value of R,
G, or B pixel according to the gradation value. For example, the
gamma correction may be carried out by a configuration providing R,
G, and B .gamma.-correction correction voltage generating circuits
for generating R, G, and B gradation voltages from R, G, and B
reference input voltages, respectively, (individual setting of R,
G, and B .gamma.-correction curve) as described in Japanese
Unexamined Patent Application Publication No. 2002-258813 (patent
reference 1).
[0165] Although the first and second embodiments divide each pixel
into two sub-pixels spatially for improving the viewing angle
dependence of the .gamma.-characteristics as shown in (A) of FIG.
3, the present invention can be applied to a case where each pixel
is divided into three or more sub-pixels. In this case, two color
imbalance ranges appear in the halftone, but the independent gamma
correction may be carried out such that the chromaticity in the
front view is shifted toward blue in each of the color imbalance
ranges for reducing the yellow tinge in the oblique view. Thereby,
it is possible to realize a display having a good color
reproducibility in the oblique view as well as in the front
view.
[0166] Also, although the first and second embodiments employ the
spatial pixel division method as described hereinabove ((A) of FIG.
3), the same problem exists and the present invention can be
applied in the case of a configuration in which one frame period is
divided into a plurality of sub-frames and an average luminance
value in the plurality of sub-frames becomes a luminance value of
each pixel, that is, in a case in which a temporal pixel division
method is employed.
INDUSTRIAL APPLICABILITY
[0167] The present invention can be applied to a color liquid
crystal display device employing the pixel division method in which
each pixel of a displayed image is composed of a predetermined
number of two or more sub-pixels obtained by spatial or temporal
division of one pixel.
* * * * *