Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-08-13
2004-05-25
Ngo, Julie-Huyen L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S129000, C349S142000
Reexamination Certificate
active
06741314
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a liquid crystal display and, more particularly, to a vertically aligned liquid crystal display which partitions the pixel region into a plurality of micro domains using a domain partitioning member to thereby make a wide viewing angle.
(b) Description of the Related Art
Generally, a liquid crystal display (“LCD”) has a top panel with a common electrode and color filters, a bottom panel with thin film transistors (“TFTs”) and pixel electrodes, and a liquid crystal layer sandwiched between the two panels. Different potentials are applied to the pixel electrodes and the common electrode to generate an electric field, which reorients the liquid crystal molecules, thereby controlling the transmittance of light to display images.
The LCD often involves a critical shortcoming of a narrow viewing angle. In order to solve such a problem, various techniques of widening the viewing angle have been developed. For instance, it has been proposed that the liquid crystal molecules may be aligned perpendicular to the top and the bottom panels while forming a predetermined pattern of openings or protrusions at the pixel electrodes and the common electrode.
When utilizing the opening pattern, for example, the tilt directions of the liquid crystal molecules are controlled by way of a fringe field generated by the openings provided both at the pixel electrodes and the common electrode, thereby widening the viewing angle.
When utilizing the protrusion pattern, on the other hand, protrusions are formed on the pixel electrodes and the common electrode provided on the top and the bottom panels, and the tilt directions of the liquid crystal molecules are controlled by way of an electric field deformed by the protrusions.
Furthermore, an opening pattern may be formed in the pixel electrodes of the bottom panel while forming a protrusion pattern on the common electrode of the top panel. The tilt directions of the liquid crystal molecules are controlled by way of the fringe field generated by the openings and the protrusions while forming a plurality of micro domains.
The LCD also often involves a shortcoming of low brightness in which the visibility becomes deteriorated at a place where circumferential light is strong. In order to enhance the brightness of the LCD, the light transmittance or the occupation ratio of the light transmission area (the aperture ratio) should be increased as much as possible. Particularly, for the LCD having pixel regions partitioned into a plurality of micro domains by domain partitioning members to thereby obtain a wide viewing angle, the aperture ratio should be increased to enhance the brightness since the light is blocked by the domain partitioning member.
In order to increase the aperture ratio, it is required that the area of the pixel electrode should be widened as much as possible while minimizing the width of the black matrix.
However, when the area of the pixel electrode is large, the distance between the neighboring pixel electrodes becomes short so that the voltages applied thereto influence each other to generate a strong fringe field near the borderline area. Such a fringe field helps forming domains where the long axes of the liquid crystal molecules are inclined perpendicular to the boundary of the pixel electrode, but hinders the domain formation where the long axes of the liquid crystal molecules are inclined parallel to the boundary of the pixel electrode. With the hindrance of the domain formation, the inclining directions of the liquid crystal molecules are dispersed, and correspondingly, texture is made at the display screen. To summarize, when the pixel electrode becomes widened, the texture increases. As shown in
FIG. 7
, the texture is seriously intensified at the left and right bottom sides (the A area) of the pixel. Furthermore, as shown in
FIG. 8
, it is expected that the texture be made in a shape of a half circle at the left and right sides (the B area) of the pixel. Meanwhile, as the width of the black matrix becomes minimized, the black matrix cannot screen the texture, resulting in deteriorated picture quality.
SUMMARY OF THE INVENTION
The invention provides an LCD where horizontal domains are arranged at both sides of the vertical domains.
In one embodiment, the liquid crystal display has a first insulating substrate, first signal lines formed on the first insulating substrate, and second signal lines formed at the first insulating substrate intersecting the first signal lines in an insulating manner. A pixel electrode is formed at each pixel region delimited by the intersection of the first and the second signal lines while being partitioned into a plurality of partitions by way of a first domain partitioning member. A thin film transistor is connected to the first and the second signal lines and to the pixel electrode. A second insulating substrate faces the first insulating substrate. A common electrode is formed on the second insulating substrate with a second domain partitioning member for partitioning the plurality of partitions into a plurality of micro domains. The micro domains have first and second horizontal micro domains and first vertical micro domains classified depending upon the average direction of the liquid crystal molecules within the relevant domains. The second horizontal micro domains are arranged between the first vertical micro domains and the second signal lines placed at the left and right sides of the first vertical micro domains. The first horizontal micro domains are disposed at at least one of the top and bottom sides of the first vertical micro domains.
The micro domains further have second vertical micro domains, disposed at at least one of the top and bottom sides of the first horizontal micro domains. The distance between the two neighboring second signal lines is varied repeatedly along a length of the lines, and the side of the pixel electrode close to the second signal line is outlined with the same pattern as the second signal line such that the pixel electrode has a narrow part and a wide part. The narrow part of the pixel electrode is partitioned into the first horizontal micro domains and the second vertical micro domains by way of the first and the second domain partitioning members, and the wide part of the pixel electrode is partitioned into the first vertical micro domains and the second horizontal micro domains by way of the first and the second domain partitioning members.
Third signal lines are formed at the first substrate while intersecting the second signal lines in an insulating manner. Subsidiary storage capacitor electrodes overlap the third signal lines in an insulating manner while being electrically connected to the pixel electrodes. The subsidiary storage capacitor electrode overlaps the second domain partitioning member.
The second domain partitioning member, in one embodiment, is an opening pattern formed at the common electrode while bearing a horizontal opening and a vertical opening. The horizontal opening has a first section including a first end with two branches and an opposite second end with two branches so as to form two of the first vertical domains and two of the second horizontal domains.
In another embodiment, the liquid crystal display includes a first insulating substrate, and a gate wire formed on the first insulating substrate with gate lines and gate electrodes. A gate insulating layer is formed on the gate wire. A semiconductor layer is formed on the gate insulating layer. A data wire is formed on the semiconductor layer with data lines, source electrodes and drain electrodes. The data lines intersect the gate lines. A protective layer is formed on the data wire having contact holes exposing the drain electrodes. Pixel electrodes are formed on the protective layer. Each pixel electrode partially overlaps the data line and the gate line while being partitioned into a plurality of partitions by way of a first opening pattern. A second insulating substrate faces the first insu
Cantor & Colburn LLP
Ngo Julie-Huyen L.
Samsung Electronics Co,. Ltd.
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