Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-10-13
2003-06-10
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C379S039000
Reexamination Certificate
active
06577366
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a liquid crystal display having a wide viewing angle, and more particularly, to a liquid crystal display of which viewing angle is made wide by patterning apertures in electrodes.
(b) Description of the Related Art
Liquid crystal displays (LCDs) typically include two substrates and a liquid crystal layer interposed between the substrates. The transmittance of light is controlled by the intensity of an electric field applied to the liquid crystal layer.
In a vertically aligned (VA) mode LCD, liquid crystal molecules take on a homeotropic orientation in which long axes of the molecules are perpendicular to the substrate. This configuration cuts off lights almost completely in an “off” state where an electric field above a certain value is not applied to the liquid crystal layer. In the normally black mode, since brightness in the off state is extremely low, a significantly higher contrast ratio can be obtained when compared to the conventional twisted nematic LCDs. However, in an “on” state, in which an electric field above a certain value is applied between the electrodes, a tilt direction of the liquid crystal molecules is irregular such that a direction of the long axes of some liquid crystal molecules becomes identical to a polarizing direction of either an upper or a lower polarizer film. When this occurs, the liquid crystal molecules are unable to rotate the polarizing direction of light, thereby blocking the light with the polarizer films. These parts of the LCD appear black, degrading the picture quality. To solve this problem, many methods of patterning electrodes are proposed. In U.S. Pat. No. 5,136,407, a method of forming line-shaped apertures on electrodes of one of the two substrates is disclosed. In U.S. Pat. No. 5,309,264, there is disclosed a method of forming “X”-shaped apertures on transparent electrodes of one of the two substrates.
In order to maintain a storage capacitance, either storage lines or gate lines are used. In the latter case, an aperture formed at a pixel above a gate may form an electric field between the gate line and a common electrode and leak lights by moving the liquid crystal material, when a voltage is applied to the gate line. This limits the design of the apertures of the electrodes. Accordingly, it is hard to design an electrode pattern that allows a bigger margin for pixel alignment. Further, in a ring gate structure, it frequently causes a high pixel defect, which leaves pixels continuously in a white state as a result of shorting the pixel electrodes with the data lines or the gate lines. This problem is difficult to repair. Finally, an aperture ratio is low since light can not be transmitted in the areas where the gate lines are formed.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide an electrode pattern design which enables a bigger margin for pixel alignment.
It is another object of the present invention to provide a method for repairing high pixel defects.
It is yet another object of the present invention to increase an aperture ratio.
A liquid crystal display according to the present invention includes a first gate line formed on a lower substrate, a first storage line formed on the lower substrate, a data line formed on the lower substrate crossing and insulated from the first gate line and the first independent line, a pixel electrode formed on the lower substrate crossing and insulated from the first storage line, and a common electrode formed on an upper substrate with an aperture dividing the pixel electrode into a plurality of sections. The outer boundary of the pixel electrode is rugged and the aperture formed on the common electrode has various shapes depending on the aspects of the present invention.
The storage line may have storage electrodes and/or cover patterns to increase a storage capacitance.
The cover patterns may overlap the adjacent pixel electrodes or data lines. Or they may just follow the boundaries of the pixel electrodes and data lines to keep a uniform distance between them.
REFERENCES:
patent: 5745195 (1998-04-01), Zhang
patent: 6229589 (2001-05-01), Koma
patent: 7-199190 (1995-08-01), None
F.C. Luo; “Active Matrix LC Displays” pp. 397-408; published 1990.
Kim Kyeong-Hyeon
Lee Kye-Hun
Park Seung-Beom
Song Jang-Kun
Dudek James
McGuireWoods LLP
Park Hae-Chan
Samsung Electronics Co,. Ltd.
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