Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-03-13
2003-01-28
Shankar, Vijay (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S087000
Reexamination Certificate
active
06512505
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display apparatus and its driving method as well as a liquid crystal display system, particularly to an active matrix type liquid crystal display apparatus of a dot successive driving system for successively driving respective pixels arranged in a matrix shape for respective line (row) in units of pixels and its driving method as well as a liquid crystal display system using the liquid crystal display apparatus.
2. Description of the Related Art
An explanation will firstly be given of a first problem which the present invention intends to resolve. According to an active matrix type liquid crystal display apparatus, normally, as switching elements of respective pixels, thin film transistors (TFT) are used.
FIG. 7
shows an example of a constitution of such an active matrix type TFT liquid crystal display apparatus. In this case, for simplicity, there is shown, for example, a case of an arrangement of four rows and four columns of pixels.
Pixels
101
are arranged in a matrix shape at intersecting portions of respectives of gate lines Vg
1
through Vg
4
and respectives of signal lines sig
1
through sig
4
in FIG.
7
. The pixels
101
are constructed by a constitution having thin film transistors TFTs gate electrodes of which are connected to the gate lines Vg
1
through Vg
4
and source electrodes (or drain electrodes) of which are connected to the signal lines sig
1
through sig
4
and hold capacitors Cs one electrode of each of which is connected to the drain electrode (or source electrode) of the thin film transistor TFT. Further, in this case, for simplifying the drawing, a liquid crystal cell LC is omitted. A pixel electrode of the liquid crystal cell LC is connected to the drain electrode of the thin film transistor TFT.
According to the pixel structure, opposed electrodes of the liquid crystal cells LC, not illustrated, and other electrodes of the hold capacitors Cs are connected to a Cs line
102
commonly among the respective pixels. Further, direct current voltage is applied on the opposed electrodes of the liquid crystal cells LC, not illustrated, and the other electrodes of the hold capacitors Cs as common voltage Vcom via the Cs line
102
.
A scanning driver
103
carries out a processing of selecting the pixels
101
in units of rows by successively scanning the gate lines Vg
1
through Vg
4
at every vertical period (1 field period). In the meantime, a source driver
104
carries out a processing of successively sampling, for example, image signals video
1
and video
2
inputted by two routes at every horizontal period (1H) and writing sampled image signals to the pixels
101
of a row selected by the scanning driver
103
.
According to the source driver
104
, specifically, sampling switches sw
1
through sw
4
are alternately connected between the respective signal lines sig
1
through sig
4
of the pixel unit and respective input signal lines
105
-
2
and
105
-
1
of the image signals video
2
and video
1
and the sampling switches sw
1
through sw
4
in pairs of twos are successively made ON in response to sampling pulses Vh
1
and Vh
2
successively outputted from respective transmitting stages
106
-
1
and
106
-
2
of shift registers.
In the case of the active matrix type TFT liquid crystal display apparatus having the above-described constitution, as a system of driving thereof, there is known a dot successive driving system for successively driving the respective pixels at every line (every row) in units of pixels. In carrying out the dot successive driving, in the case of a 1H inversion driving system, in one horizontal line, the sampling switches sw
1
through sw
4
are made ON in a dot successive manner by the sampling pulses Vh
1
and Vh
2
and as shown by
FIG. 8
, image signals in the same polarity (video
1
and video
2
are in the same polarity) are written to the respective pixels
101
via the respective signal lines sig
1
through sig
4
. As a result, as shown by
FIG. 9
, the image signals in the same polarity (+/−) are written to contiguous left and right ones of the pixels.
In the meantime, resistor components RCs are present between the contiguous left and right ones of the respective pixels in the Cs line
102
, further, parasitic capacitances c
1
are present between the Cs line
102
and the signal lines sig
1
through sig
4
and accordingly, a differentiating circuit is formed by the resistor component RCs, the hold capacitor Cs and the parasitic capacitance c
1
and accordingly, in writing the image signals video
1
and video
2
, the image signals video
1
and video
2
are inputted to the Cs lines
102
and the gate lines Vg
1
through Vg
4
via the hold capacitors Cs and the parasitic capacitances c
1
.
Thereby, as shown by
FIG. 8
, potential VCs of the Cs line
102
is deviated in a direction of the same polarity of the image signals video
1
and video
2
(&Dgr;VCs) and accordingly, cross talk in the horizontal direction (hereinafter, abbreviated as horizontal cross talk) shown by
FIG. 10
becomes significant, a failure in shading is caused and image quality is considerably deteriorated. In
FIG. 10
, a portion indicated by a black region designates an actual image
111
which is actually displayed, a false image (a portion indicated by a dotted region)
112
is produced on a side of the actual image
111
in the horizontal direction.
Further, during a time period in which the pixel
101
holds pixel information in one field period, potential Vsig of the signal lines sig
1
through sig
4
is deviated at every “H” (&Dgr;Vsig) Here, in the case of the 1H inversion driving system, the polarity of the image signals written to the contiguous left and right ones of the pixels stays the same and accordingly, the deviation &Dgr;Vsig of the potential of the signal lines sig
1
through sig
4
is increased.
Further, in respectives of the pixels
101
, parasitic capacitances are present also between the source/drain electrodes of the thin film transistors TFT and the respectives of the signal lines sig
1
through sig
4
and accordingly, the deviation &Dgr;Vsig of the potential of the signal lines sig
1
through sig
4
is inputted to the pixels by source/drain couplings of the thin film transistors and accordingly, cross talk in the vertical direction (hereinafter, abbreviated as vertical cross talk) becomes significant to thereby constitute a factor of a failure in image quality similar to the horizontal cross talk.
There is provided the dot inversion driving system as a driving method of preventing a deviation &Dgr;Vcs of the potential of the Cs line
102
and the deviation &Dgr;Vsig of the potential of the signal lines sig
1
through sig
4
from causing. In the case of the dot inversion driving system, the two image signals video
1
and video
2
are inputted in inverse polarities (however, similar to the case of the 1H inversion driving system, respective polarities of the image signals video
1
and video
2
in the inverse polarities are inverted at every “H”). Thereby, when the switches sw
1
and sw
2
are made ON in response to the sampling pulse Vh
1
, as shown by
FIG. 11
, the image signal video
1
and the image signal video
2
are simultaneously written in the inverse polarities and accordingly, the deviations &Dgr;Vcs and &Dgr;Vsig of the potential are canceled between the contiguous ones of the pixels and accordingly, there poses no problem of the failure in image quality as in the case of the 1H inversion driving system.
However, in the case of the above-described dot inversion driving system, as is apparent from
FIG. 12
, the polarities of the image signals video
1
and video
2
written to the contiguous left and right ones of the pixels differ from each other and accordingly, influence of an electric field of a contiguous one of the pixel is effected. Then, a domain (light deficient domain)
122
is produced at corners of an opening portion
121
, the portion cannot be used as the opening portion
121
and acc
Kitagawa Hideyuki
Maekawa Toshikazu
Noda Kazuhiro
Uchino Katsuhide
Kananen, Esq. Ronald P.
Patel Nitin
Rader & Fishman & Grauer, PLLC
Shankar Vijay
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