Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-01-22
2004-07-06
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S129000
Reexamination Certificate
active
06760087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a liquid crystal display (LCD), and more particularly, to a multi-domain vertical alignment (MVA) liquid crystal display.
2. Description of the Related Art
Currently, the development of liquid crystal display is directed towards a large display quantity, a high brightness, a high contrast, a large viewing angle, a large area and a full color display. To resolve the problem of viewing angle, the displaying liquid crystal area of the liquid crystal display is divided into multiple domains, so that liquid crystal molecules are inclined towards different angles to increase the viewing angle of the liquid crystal display.
In the conventional multi-domain vertical alignment liquid crystal display, a thin-film transistor (TFT) array substrate and a substrate having a color filter are provided. A lower polarization plate and an upper polarization plate are provided under the TFT array substrate and on the substrate having a color filter, respectively. The upper and lower polarization plates allow only a vertical straight polarized light to pass. A liquid crystal layer is disposed between the upper and lower polarization plates. The direction of the long axis of the liquid crystal layer is vertical to the TFT array substrate and the substrate having the color filter. The long axis of the liquid crystal layer is parallel to the electric field, so that the rotation speed of the molecules is slow at the beginning of the rotation. When the direction of the long axis becomes vertical to the electric field, the rotation speed of the molecules is faster. Therefore, a pre-tilt angle is required control the aligning direction of the liquid crystal, so as to precisely control the inclining direction of the liquid crystal molecules. A commonly seen technique is forming slits and protrusions on two surfaces of the TFT array substrate and the substrate having the color filter.
Referring to
FIG. 1
, a conventional MAVLCD is shown. Pixel electrodes
101
and slits
102
are formed on a TFT array substrate
100
, while the substrate having the color filter
104
has pixel electrodes
105
, which includes a protrusion
106
. After packaging the TFT array substrate
100
and the substrate having the color filter
104
, there is a protrusion
106
on the TFT array substrate
100
between two slits
102
. That is, the slits
102
and the protrusion
106
are alternately arranged without being positioned in the same vertical line. By applying a voltage, the liquid crystal molecules between the substrates
100
and
104
are inclined towards the same direction due to formation of the protrusion
106
and the slits
102
.
Referring to
FIG. 2
, another conventional MAVLCD is shown. A TFT array substrate
200
having pixel electrodes
201
and slits
202
a
is provided. A substrate having a color filter
204
with pixel electrodes
205
and a slit
202
b
is also provided. After packaging the substrates
200
and
204
, the slit
202
b
is between the slits
202
a
. That is, the slits
202
a
and the slit
202
b
are alternately arranged without being positioned in the same vertical line. By applying a voltage, the liquid crystal molecules between the substrates
200
and
204
are inclined towards a predetermined direction dependent to the slits
202
a
and
202
b.
The conventional MVALCD uses slits or a combination of slits and protrusions to process surfaces of the TFT array substrate and the substrate having a color filter. The fabrication cost is high.
In addition, the misalignment of the slit and protrusion may occur while packaging the substrates. The quality of the liquid crystal display is seriously affected.
SUMMARY OF THE INVENTION
The present invention provides a multi-domain vertical array liquid crystal display, on which protrusions and slits are formed on the thin-film transistor array only. Therefore, the alignment of slits and protrusions on two substrates is not required. The quality of the liquid display is not affected by misalignment.
The multi-domain vertical array liquid crystal display further has a dielectric layer formed to cover the protrusions and slits. The dielectric layer on the protrusions is thinner, or alternatively, the pixel electrodes on the protrusions are exposed, so that the thin-film transistor array substrate is flat, and liquid crystal molecules are divided into multiple domains to display.
Accordingly, the present invention provides a multi-domain vertical array liquid crystal display, including a substrate having a color filter, a liquid crystal layer and a thin-film transistor array substrate. The thin-film transistor array substrate has thin-film transistors and pixel electrodes arranged in an array. The pixel electrode has a plurality of protrusions and slits thereon. A dielectric layer with a flat top surface is formed to cover the pixel electrodes, such that the dielectric layer on the protrusions is thinner than other positions. Or alternatively, the surfaces of the pixel electrodes on the protrusions are exposed. Since the dielectric layer on the protrusions is thinner, or the pixel electrodes on the protrusions are exposed, the electric potential on the protrusion is higher than that on other positions. By alternately arranging the protrusions and the slits and the formation of the dielectric layer, the pixel electrodes are planarized. Further, the electric field generated by the pixel electrodes is twisted, so that the liquid crystal molecules are inclined towards different directions. The liquid crystal layer on the same pixel electrode is divided into multiple domains to form the multi-domain vertical array liquid crystal display.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
REFERENCES:
patent: 6008875 (1999-12-01), Ikeno et al.
patent: 6424396 (2002-07-01), Kim et al.
patent: 6485997 (2002-11-01), Lee et al.
Chen Po-Lun
Wu Ivan Yang-En
AU Optronics Corporation
Chung David Y
J.C. Patents
Kim Robert H.
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