Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-12-12
2004-11-23
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S043000
Reexamination Certificate
active
06822718
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display driven according to a dot inversion method using a data driver driven according to a column inversion method, wherein all liquid crystal cells of a liquid crystal display panel express images at a uniform brightness.
2. Description of the Related Art
Generally, liquid crystal displays typically include a liquid crystal display panel having a plurality of liquid crystal cells arranged in a matrix pattern and driving circuit for driving the liquid crystal display panel. To display pictures, liquid crystal displays control light transmittance characteristics of the liquid crystal cells in accordance with inputted video signals.
The liquid crystal cells are located at areas defined by crossings of gate lines and data lines. Each the liquid crystal cell is provided with a common electrode and a pixel electrode with which an electric field may be generated. Each pixel electrode is connected to a corresponding data line via a switching device such as a thin film transistor (TFT). A terminal of a TFT is connected to a gate line such that video signals may be applied to corresponding pixel electrodes. The driving circuit includes a gate driver for driving gate lines, a data driver for driving data lines, and a common voltage generator for driving the common electrode.
The gate driver sequentially scans the gate lines of the liquid crystal display panel, supplies gate signals to gate lines, and drives the liquid crystal cells on the liquid crystal display panel one gate line at a time. Whenever a gate signal is supplied to a gate line, the data driver supplies suitable video signals to each of data lines crossing that scanned gate line while the common voltage generator supplies common voltage signals to the common electrode. Depending on the video signal applied to the data line, an orientation of molecules of liquid crystal material provided within the liquid crystal cell, between the pixel and common electrodes, may be altered and the light transmittance of the liquid crystal cell may be controlled. Accordingly, as the light transmittances of each of the liquid crystal cells in the liquid crystal display panel are individually controlled, the liquid crystal display panel may display a picture.
FIG. 1
illustrates a schematic view of a related art liquid crystal display.
Referring to
FIG. 1
, liquid crystal displays typically include a liquid crystal display panel
2
having a plurality of liquid crystal cells arranged in a matrix pattern, a gate driver
4
for driving gate lines GL
1
to GLn arranged in the liquid crystal display panel
2
, and a data driver
6
for driving data lines DL
1
to DLm also arranged in the liquid crystal display panel
2
.
Each of the liquid crystal cells include a TFT that responds to gate signals applied to the gate lines GL
1
to GLn by supplying video signals, applied to the data lines DL
1
to DLm, to the liquid crystal cells. Each liquid crystal cell can be represented as a pixel electrode and a common electrode connected to each other via a TFT and a liquid crystal capacitor Clc. A storage capacitor (not shown), for maintaining a voltage of the video signal, is included within the liquid crystal cell. The storage capacitor maintains the charge within liquid crystal capacitor Clc until the next video signal is supplied.
Storage capacitors of liquid crystal cells are formed between preceding gate electrodes and pixel electrodes of each liquid crystal cell. The gate driver
4
sequentially applies gate signals to gate lines GL
1
to GLn to drive the corresponding TFTs. The data driver
6
converts inputted video data into analog video signals and supplies analog video signals, specific to the scanned gate line, to the data lines DL
1
to DLm during the period when the gate signal is supplied to the scanned gate line. Additionally, the data driver
6
converts inputted video data into analog video signals using gamma voltages supplied from a gamma voltage generator (not shown).
Liquid crystal cells within liquid crystal display panels such as those illustrated in
FIG. 1
may be driven according to various inversion methods including frame, line, column, and dot inversion methods.
When driven according to the frame inversion method, the polarity of video signals supplied to the liquid crystal cells is inverted every frame.
Referring to
FIGS. 2A and 2B
, when driven according to the line inversion method, the polarity of video signals supplied to liquid crystal cells connected to a gate line is opposite the polarity of video signals supplied to liquid crystal cells connected to gate lines adjacent that gate line. Further, the polarities of the video signals applied to the liquid crystal cells are inverted every frame. Driving liquid crystal cells by the line inversion method, however, is disadvantageous in that a flicker phenomenon is induced in horizontal lines due to electrical cross-talk between liquid crystal cells arranged along the gate lines.
Referring to
FIGS. 3A and 3B
, when driven according to the column inversion method, the polarity of video signals supplied to liquid crystal cells connected to a data line is opposite the polarity of video signals supplied to liquid crystal cells connected to data lines adjacent that data line. Further, the polarities of the video signals applied to the liquid crystal cells are inverted every frame. Driving liquid crystal cells by the column inversion method, however, is disadvantageous in that a flicker phenomenon is induced in vertical lines due to electrical cross-talk between liquid crystal cells arranged along the data lines.
Referring to
FIGS. 4A and 4B
, when driven according to the dot inversion method, the polarity of a video signal supplied to a liquid crystal cell is opposite the polarity of video signals supplied to adjacent liquid crystal cells (e.g., liquid crystal cells connected to adjacent gate and data lines). Further, the polarities of the video signals applied to the liquid crystal cells are inverted every frame. Driving liquid crystal cells by the dot inversion method offsets any flicker phenomenon that may be induced between vertically or horizontally adjacent liquid crystal cells. Accordingly, pictures generated by the liquid crystal display panel driven using the dot inversion method have superior qualities over pictures generated by liquid crystal display panels driven using other inversion methods.
Use of the dot inversion method, however, is disadvantageous in that the polarity of video signals supplied from the data driver to the data line need to be inverted in horizontal and vertical directions and individual pixel voltages required by the dot inversion method are typically greater than those required by other inversion methods. Accordingly, liquid crystal displays driven using a dot inversion method typically consume a relatively large amount of power during their operation.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to liquid crystal display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention provides a liquid crystal display driven by a dot inversion method using a data driver driven by a column inversion method, wherein such a liquid crystal display is capable of consuming a relatively small amount of power during its operation.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. These and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display includin
Choi Seung Kyu
Park June Ho
Song Sang Moo
Dudek James A.
LG.Philips LCD Co. , Ltd.
McKenna Long & Aldridge LLP
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