Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-12-19
2004-11-30
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S130000
Reexamination Certificate
active
06825905
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display having a bent alignment of liquid crystal molecules to obtain a wide viewing angle and a fast response time.
(b) Description of the Related Art
Liquid crystal displays typically include a first substrate having common electrodes and a color filter, and a second substrate having thin film transistors and pixel electrodes. The first substrate and the second substrate are provided substantially in parallel with a predetermined gap therebetween, and liquid crystal is injected between the two opposing substrates. An electric field is formed between the substrates by applying different voltages to the pixel electrodes and common electrodes. Accordingly, the alignment of liquid crystal molecules of the liquid crystal material is varied to thereby control the transmittance of incident light.
Various types of liquid crystal displays have been developed to improve response times and viewing angle. They include the HAN (hybrid aligned nematic) mode liquid crystal display and the OCB (optically compensated bend) mode liquid crystal display. The OCB mode LCD includes an electrode formed on each opposing substrate, the electrodes acting to form an electric field that is perpendicular to the two substrates; liquid crystal injected between the two substrates; and an alignment layer formed on each substrate, the alignment layers providing a force to align the liquid crystal molecules in a direction substantially parallel to the two substrates.
In the OCB mode LCD, a symmetrical arrangement is realized about an imaginary center plane between the two substrates and parallel to the same. That is, the liquid crystal molecules are aligned substantially parallel to the substrates, then are increasingly slanted until reaching this center plane where the liquid crystal molecules are substantially perpendicular to the two substrates. A wide viewing angle is achieved as a result. To obtain such a bent alignment of the liquid crystal molecules, a horizontal alignment agent that is oriented in the same direction is used and a high voltage is initially applied. Also, since the liquid crystal molecules move in the same orientation when the LCD is operated, a wide viewing angle and a fast response time are realized.
However, in such a LCD, in areas where unit pixels begin, a smooth bending alignment of the liquid crystal molecules cannot be aligned in a smooth bending pattern, thereby limiting the display characteristics. This is a result of the opposing directions of the bending alignment of the liquid crystal molecules and the bending direction of the electric field at edges of the pixel electrodes. That is, unlike the common electrode, which is formed over an entire surface of the substrate, the pixel electrodes are divided for each pixel region such that this opposing direction of LC molecule alignment and electric field occurs at the edges of the pixel electrodes.
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 a liquid crystal display that realizes a stable bent alignment of liquid crystal molecules such that a wide viewing angle and fast response times are obtained.
To achieve the above object, the present invention provides a liquid crystal display comprising a first substrate including wiring, which intersects to define unit pixels, and a first electrode formed in each unit pixel; a second substrate provided opposing the first substrate at a predetermined distance from the same, and including a second electrode formed over an entire surface of the second substrate, the second electrode generating an electric field with the first electrode; and a liquid crystal layer injected between the first and second substrates and including liquid crystal molecules that are horizontally oriented in one direction, the liquid crystal molecules, as a result of the electric field generated between the first and second substrates, having a symmetrically bent alignment about an imaginary center plane parallel to the first and second substrates at a center position therebetween, wherein the first electrode is protruded in a direction toward the second substrate at edges where orientation for the liquid crystal molecules starts.
According to a feature of the present invention, a protrusion pattern is formed under the first electrode.
According to another feature of the present invention, a thickness of the protrusion pattern is 1-4 &mgr;m.
According to yet another feature of the present invention, the wiring includes gate lines for transmitting gate signals, and data lines intersecting the gate lines and transmitting image signals.
According to still yet another feature of the present invention, the liquid crystal display further comprises storage capacitance wiring formed on a same layer as the gate lines but separated from the same, the storage capacitance wiring overlapping the first electrode.
According to still yet another feature of the present invention, the first substrate includes a thin film transistor having a gate electrode formed at areas where the gate lines intersect the data lines and connected to the gate lines, a source electrode connected to the data lines, a drain electrode opposing the source electrode with respect the gate electrode, and a semiconductor layer.
According to still yet another feature of the present invention, the protrusion pattern is formed on a same layer as organic insulation material, the gate lines, or the semiconductor layer.
According to still yet another feature of the present invention, first and second orientation layers are formed respectively on the first and second substrates, the orientation layers providing an orienting force to the liquid crystal molecules in an identical direction horizontal to the substrates.
According to still yet another feature of the present invention, the liquid crystal layer has a positive anisotropic dielectricity.
In another aspect, the present invention provides a liquid crystal display comprising a first substrate including wiring, which intersects to define unit pixels, and a first electrode formed in each unit pixel; a second substrate provided opposing the first substrate at a predetermined distance from the same, and including a second electrode formed over an entire surface of the second substrate, the second electrode generating an electric field with the first electrode; a liquid crystal layer injected between the first and second substrates and including liquid crystal molecules that are horizontally oriented in one direction, the liquid crystal molecules, as a result of the electric field generated between the first and second substrates, having a symmetrically bent alignment about an imaginary center plane parallel to the first and second substrates at a center position therebetween; and a protrusion pattern formed on the first substrate or second substrate, the protrusion pattern forming a slanted surface that opposes an orientation direction at edges of the unit pixels where orientation of the liquid crystal molecules begins or ends.
According to a feature of the present invention, the liquid crystal molecules have a larger pretilt angle with respect to the first and second substrates at the edges of the unit pixels than at other areas.
According to another feature of the present invention, the wiring includes gate lines for transmitting gate signals, and data lines intersecting the gate lines and transmitting image signals.
According to yet another feature of the present invention, the first substrate includes a thin film transistor having a gate electrode formed at areas where the gate lines intersect the data lines and connected to the gate lines, a gate insulation layer covering the gate electrode, a semiconductor layer formed over the gate insulation layer, a source electrode connected to the data lines, and a drain electrode opposing the source electrode
Lee Chang-Hun
Park Seung-Beom
Song Jang-Kun
Chung David Y.
McGuireWoods LLP
Parker Kenneth
Samsung Electronics Co,. Ltd.
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