Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1997-10-16
2001-02-13
Malinowski, Walter J. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06188459
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to liquid crystal display (LCD) devices and methods of fabrication therefor, more particularly, to in-plane switching (IPS) type LCD devices and methods of fabrication therefor.
BACKGROUND OF THE INVENTION
Liquid crystal display (LCD) devices are commonly used flat panel display devices. LCD devices include twisted-nematic (TN) type devices, which may have switching elements such as thin-film transistors (TFTs) for controlling respective pixels, and super-twisted-nematic (STN) type devices. TN and STN devices typically include first and second substrates which have opposing transparent common and pixel electrodes formed thereon, respectively, with a liquid crystal material being sandwiched between the substrates. Unfortunately, TN and STN type LCD devices typically have narrow viewing angles, especially in an up-down direction. Furthermore, since the common electrode and the pixel electrodes are formed on separate substrates, and the two substrates may connected in order to convey signals therebetween, numerous and difficult process steps may be required to produce a display device.
To avoid these problems, in-plane switching (IPS) type LCD devices have been developed. In an IPS LCD device, a plurality of pixel electrodes and common electrodes are formed on the same substrate, as described in European Patent Application No. 93307154.0. The electric field developed between the pixel electrode and the common electrode, which affects the orientation of the molecules of the liquid crystal, is aligned parallel to the substrate, in contrast to the perpendicular electric fields produced by the electrodes of a typical TN or STN LCD device. Unfortunately, however, conventional IPS LCD devices may have an undesirably small aperture ratio, especially when all the electrodes are formed on one substrate.
SUMMARY OF THE INVENTION
In light of the foregoing, it is an object of the present invention to provide an in-plane switching (IPS) type liquid crystal display (LCD) device with improved aperture ratio.
This and other objects, features and advantages are provided according to the present invention by IPS type LCD devices in which common electrodes and pixel electrodes of a pixel have a width minimized according to a design rule such as a maximum resistance, and are spaced to provide the same maximum gap therebetween, except for a different gap separating an outlying electrode from an adjacent electrode. This nonuniform gap may be located on only one side of the pixel, separating an outlying electrode nearest a data line from an adjacent pixel, with the outlying electrode being separated from the data line by a gap which is minimized according to a design rule such as a photolithographic margin and/or a maximum coupling capacitance. Alternatively, the pixel may have two non-uniform gaps which separate two respective outlying electrodes from respective adjacent electrodes. By providing the nonuniform gaps, increased aperture ratio may be achieved over pixels in which common and pixel electrodes are uniformly spaced.
In particular, according to the present invention, a panel for a liquid crystal display device includes a substrate and a data line on the substrate, extending along a first direction. A pixel is formed on the substrate, disposed adjacent the data line, and includes a plurality of spaced apart elongate pixel electrodes extending parallel to the data line, and a plurality of spaced apart elongate common electrodes extending parallel to the data line and interspersed among the pixel electrodes such that a respective pixel electrode is disposed adjacent a respective common electrode. The common and pixel electrodes define a plurality of gaps, a respective one of the gaps separating a common electrode and a pixel electrode, the plurality of gaps having nonuniform widths. Preferably, the plurality of gaps includes a first group of gaps having a first width and a second group of gaps having a second width. According to one embodiment, the first group of gaps includes all of the plurality of gaps except a gap between one common electrode nearest the data line and a pixel electrode nearest the one common electrode. According to another embodiment, the first group of gaps includes all of the plurality of gaps except a gap between a first common electrode nearest the data line and a pixel electrode nearest the first common electrode, and a gap between a second common electrode furthest from the data line and a pixel electrode nearest the second common electrode.
Preferably, the common electrodes and the pixel electrodes have a minimum width according to a first design rule, and the data line has a minimum width according to a second design rule; the first and second design rules may include a resistance, for example. The first gap width preferably is a maximum width according to a third design rule such as a driving voltage, while the second gap width preferably is a minimum width according to a fourth design rule such as a photolithographic margin and/or a coupling capacitance. The data line and a nearest one of the pixel electrodes and the common electrodes preferably define a gap therebetween having a minimum width according to a fifth design rule such as a photolithographic margin and/or a coupling capacitance.
According to method aspects of the present invention, a panel of a liquid crystal display device is fabricated by forming a data line on a substrate, extending along a first direction. A pixel is formed on the substrate adjacent the data line, the pixel including a plurality of spaced apart elongate common electrodes extending parallel to the data line and a plurality of spaced apart elongate pixel electrodes extending parallel to the data line and interspersed among the common electrodes such that a respective one of the pixel electrodes is disposed adjacent a respective common electrode. The common and pixel electrodes define a plurality of gaps, a respective one of the gaps separating a common electrode and a pixel electrode, the plurality of gaps having nonuniform widths. Preferably the plurality of gaps includes a first group of gaps having a first width and a second group of gaps having a second width. Preferably, the common electrodes and the pixel electrodes have a minimum width according to a first design rule, the data line has a minimum width according to a second design rule, the first width is a maximum width according to a third design rule, the second width is a minimum width according to a fourth design rule, and the data line and a nearest one of the pixel electrodes and the common electrodes define a gap therebetween having a minimum width according to a fifth design rule. Improved IPS type LCD devices may thereby be formed.
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Malinowski Walter J.
Myers Bigel & Sibley & Sajovec
Samsung Electronics Co,. Ltd.
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