Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
1998-07-08
2001-07-03
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S039000
Reexamination Certificate
active
06256076
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to display devices and methods of forming display devices, and more particularly to liquid crystal display devices and methods of forming liquid crystal display devices.
BACKGROUND OF THE INVENTION
In order to minimize the space required by display devices, research into the development of various flat panel display devices such as LCD display devices, plasma display panels (PDP) and electro-luminescence displays (EL) has been undertaken to displace larger cathode-ray tube displays (CRT) as the most commonly used display devices. Particularly, in the case of LCD display devices, liquid crystal technology has been explored because the optical characteristics of liquid crystal material can be controlled in response to changes in electric fields applied thereto. As will be understood by those skilled in the art, a thin film transistor liquid crystal display (TFT LCD) typically uses a thin film transistor as a switching device and the electrical-optical effect of liquid crystal molecules to display data visually.
At present, the dominant methods for fabricating liquid crystal display devices and panels are typically methods based on amorphous silicon (a-Si) thin film transistor technologies. Using these technologies, high quality image displays of substantial size can be fabricated using low temperature processes. As will be understood by those skilled in the art, conventional LCD devices typically include a transparent (e.g., glass) substrate with an array of thin film transistors thereon, pixel electrodes, orthogonal gate and data lines, a color filter substrate and liquid crystal material between the transparent substrate and color filter substrate. The use of a-Si TFT technology typically also requires the use of separate peripheral integrated circuitry to drive the gates and sources (i.e., data inputs) of the TFTs in the array. In particular, gate driving signals from a gate driving integrated circuit are typically transmitted to the gate electrodes of TFTs in respective rows and data driving signals from a data driving integrated circuit are typically transmitted to the source electrodes of TFTs in respective columns. A display is typically composed of a TFT substrate in which a plurality of liquid crystal pixels are formed. Each pixel typically has at least one TFT and a pixel electrode coupled to the drain of the respective TFT. Accordingly, the application of a gate driving signal to the gate of a TFT will electrically connect the pixel electrode of a respective TFT to the data line connected thereto.
Referring now to
FIG. 1
, a first TFT LCD display cell of a conventional TFT LCD display device is illustrated. Each cell comprises a TFT transistor having a source electrode connected to a data line (DL), a gate electrode connected to a gate line (GL) and a drain electrode connected to a respective pixel electrode internal to the cell. As will be understood by those skilled in the art, a storage capacitor (Cst) is utilized to sustain the pixel electrode voltage during holding periods and the liquid crystal capacitor (C
LC
) is connected in series between a respective pixel electrode and a common electrode (Vcom) of a color filter substrate. The storage capacitor also has an electrode connected to a storage electrode line (SL). The storage capacitors of adjacent display cells in a row thereof may also have electrodes which are connected to the storage electrode line (SL). However, as will be understood by those skilled in the art, the use of an independent storage electrode line (SL) for each row of display cells may decrease the display device's aperture ratio.
Referring now to
FIG. 2
, another conventional TFT LCD display device is illustrated. Each cell comprises a TFT transistor having a source electrode connected to a data line (DL), a gate electrode connected to a gate line (GL) and a drain electrode connected to a respective pixel electrode internal to the cell. As illustrated, a liquid crystal capacitor (C
LC
) in each cell is connected in series between a respective pixel electrode and a common reference potential (Vcom) and the storage capacitor in each cell is connected in series between a respective pixel electrode and a next lower order gate line (GL). Unfortunately, although the aperture ratio of the device of
FIG. 2
may be greater than the aperture ratio of the device of
FIG. 1
, the parasitic capacitance of each gate line (GL) is relatively high in the device of FIG.
2
. Moreover, in the event any of the TFTs in the devices of
FIGS. 1 and 2
are defective, the voltage on the corresponding pixel electrode may be driven to a level which is significantly different than the value of the data to be loaded into the defective cell and this can corrupt the fidelity of the final displayed image.
Accordingly, notwithstanding the above described display devices, there still continues to be a need for improved display devices which have high aperture ratio and reduced parasitic gate line capacitance.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to form a storage capacitor for an LCD without decreasing the aperture ratio and without increasing the number of the wires.
It is another object of the present invention to improve the display characteristic of an LCD.
These and other objects, features and advantages are provided, according to the present invention, by providing a storage capacitor having two terminals connected to drain terminals of different pixels. The liquid crystal display having the storage capacitor may be a dot inversion driving type.
In detail, according to the present invention, the liquid crystal display includes a plurality of gate lines and data lines which transmit scanning signals and image signals from outside, respectively. A plurality of pixels are arranged in a matrix shape, and each pixel has a liquid crystal capacitor having a first and a second terminals and a switching element having a first to a third terminals. The first and the second terminals of the switching element are connected to the gate line and the data line respectively, and the third terminal is connected to the first terminal of the liquid crystal capacitor. The second terminal of each liquid crystal capacitor is connected to a reference voltage. The liquid crystal display also includes a plurality of storage capacitors, and each storage capacitor has a first terminal and a second terminal connected to the third terminals of the switching elements of different pixels. In the dot inversion driving, the first terminals of the liquid crystal capacitors of adjacent pixels in a row of the matrix are applied with image signals having different polarities relative to the reference voltage. Here, it is preferable that the different pixels are adjacent pixels.
According to the present invention, these and other objects, features and advantages are also provided by providing a storage capacitor electrode on a substrate for a liquid crystal display panel having a pixel electrode and a common electrode. The storage capacitor electrode overlaps one drain electrode via a gate insulating layer, and is connected to the another drain electrode through a contact hole in the gate insulating layer.
In particular, a liquid crystal display panel according to the present invention includes a gate wire having a gate line transmitting a scanning signal from outside and a plurality of gate electrodes connected thereto, a plurality of linear common electrodes and a plurality storage capacitor electrodes. The gate wire, the common electrodes and the storage capacitor electrodes are formed on a substrate and separated from one another. The gate wire and the common electrodes and the storage capacitor electrodes are covered with a gate insulating layer which has a plurality of contact holes exposing the storage capacitor electrodes. A plurality of channel layers are formed on the gate insulating layer over the gate electrodes, and a plurality of contact layers are formed on the channel layers. Each
Bae Byung-Seong
Na Byoung-Sun
Yuh Jin-Tae
Myers Bigel & Sibley & Sajovec
Nguyen Dung
Samsung Electronics Co,. Ltd.
Sikes William L.
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