Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-12-27
2003-12-30
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S130000
Reexamination Certificate
active
06671018
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a liquid crystal display.
(b) Description of the Related Art
Liquid crystal displays (LCDs) typically have a structure in which liquid crystal material is sandwiched between two substrates. Transparent electrodes are formed on inner surface of the substrates. An electric field applied to the liquid crystal material, controls the alignment of molecules of the liquid crystal material, thereby enabling the transmittance of incident light.
A twisted-nematic (TN) LCD includes two glass substrates which have transparent electrodes formed on the inner surface; liquid crystal material provided between the two glass substrates to form a liquid crystal layer; and first and second polarizing films provided on the outer surface of the substrates, the polarizing films acting to polarize light. In a state where no voltage is applied to the liquid crystal material, long axes of the liquid crystal molecules are roughly parallel. However, since the molecules align themselves to grooved surfaces of the substrates, by providing the substrates such that the grooves on one are perpendicular to the grooves on the other, the molecules between the substrates are twisted by 90 degrees. When a sufficient electric field is applied to the liquid crystal layer, the long axes of the liquid crystal molecules rearrange themselves vertically, allowing light to pass through untwisted.
However, with the TN liquid crystal display described above, light is not completely blocked when a voltage is not applied to the liquid crystal material. This is particularly true in the normally black mode. Accordingly, a low contrast ratio results. To remedy this problem, a vertically-aligned twisted-nematic (VATN) liquid crystal display is proposed in U.S. Pat. No. 3,914,022 (“Eurodisplay '93”, pp. 158-9, Takahashi et. al.).
With the VA-TN liquid crystal display, in a state where an electric field is not applied to the liquid crystal material, the liquid crystal molecules are perpendicular to the substrates such that light is completely blocked (together with the polarizing films) when a voltage is not applied. That is, in a normally black mode, since a brightness of an off state is extremely low, a higher contrast ratio than that of the conventional TN liquid crystal display can be obtained. However, in the presence of an electric field, the liquid crystal molecules are irregularly inclined with respect to the substrates. Thus, it creates areas where the direction of the long axes of some of the liquid crystal molecules conforms to the polarizing direction of the first or second polarizing films. In such areas, the liquid crystal molecules cannot induce the rotation of the polarizing direction and the light is completely blocked by the polarizing films. Therefore, these areas appear as black on the screen, degrading picture quality.
Aperture patterns are formed on the two substrates to solve this problem so that the electric field generated between the substrates has a predetermined slantto achieve regular alignment of the liquid crystal molecules. However, it reduces the electrode area and decreases the intensity of the electric field applied to the liquid crystal molecules. Accordingly, a response speed of the liquid crystal molecules is reduced.
Further, in order to form the aperture pattern on the electrodes of the color filter substrate, the electrodes must be formed on an organic insulation layer, after which the patterning is performed. This additional process decreases productivity. Also, it is difficult to design the aperture pattern or electrode pattern that can divide the liquid crystal molecules and align them in various regions while taking into account viewing angle direction. Finally, different pixel structures require different designs.
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 having a wide viewing angle.
To achieve the above object, the present invention provides a liquid crystal display comprising a first substrate including first electrodes; a second substrate including second electrodes, the second substrate being arranged substantially in parallel with the first substrate and with a predetermined gap therebetween; a liquid crystal layer formed by injecting liquid crystal material between the first and second substrates, long axes of liquid crystal molecules of the liquid crystal layer being arranged vertically to the first and second substrates; and first and second orientation layers formed on the first and second substrates, respectively, and providing an orientation force to the liquid crystal molecules such that the long axes of the liquid crystal molecules are slanted or twisted 0 to 10°.
According to a feature of the present invention, orientation directions of the first and second orientation layers are identical.
According to another feature of the present invention, orientation directions of the first and second orientation layers are different.
According to yet another feature of the present invention, the liquid crystal layer has a negative dielectric anisotropy.
According to still yet another feature of the present invention, a polarizing film for polarizing light is provided on outer surfaces of each of the first and second substrates.
According to still yet another feature of the present invention, a light transmission axis of the polarizing film on the first substrate is either perpendicular or parallel to a light transmission axis of the polarizing film on the second substrate.
According to still yet another feature of the present invention, the first electrodes are patterned in a slit configuration in a single direction.
According to still yet another feature of the present invention, the first electrodes are arranged in a direction corresponding to an orientation direction of the liquid crystal molecules.
According to still yet another feature of the present invention, the first electrodes are arranged in a direction that is different from an orientation direction of the liquid crystal molecules.
According to still yet another feature of the present invention, an angle between a longitudinal direction of the first electrodes and the orientation direction of the liquid crystal molecules is 0 to 10°.
According to still yet another feature of the present invention, the first electrodes are pixel electrodes for transmitting image signals, and are formed in each unit pixel area.
According to still yet another feature of the present invention, the liquid crystal display further comprises thin film transistors, the thin film transistors including gate lines for transmitting scanning signals; data lines for transmitting image signals, the data lines being insulated from and intersecting the gate lines to form pixel regions; gate electrodes provided at areas where the gate lines and data lines cross, the gate electrodes being connected to the gate lines; source electrodes connected to the data lines; and drain electrodes connected to the pixel electrodes.
According to still yet another feature of the present invention, the pixel electrodes are formed on a same layer as the gate lines or data lines.
According to still yet another feature of the present invention, the pixel electrodes are made of a transparent conductive material such as indium tin oxide or indium zinc oxide, or are made of a non-transparent conductive material.
According to still yet another feature of the present invention, the pixel electrodes are arranged in the same direction as the data line or gate lines.
According to still yet another feature of the present invention, protrusions are formed on the first substrate and/or the second substrate to provide a pretilt angle to the liquid crystal molecules.
According to still yet another feature of the present invention, an angle between a surface of the protrusions and a surface of the first and/or second substrate is 2 to 45°.
According to still yet
Lee Chang-Hun
Mun Joong-Hyun
Shim Jung-Uk
Akkapeddi P. R.
Kim Robert H.
McGuireWoods LLP
Samsung Electronics Co,. Ltd.
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