Vertically aligned liquid crystal display

Details Vertically aligned liquid crystal display Vertically aligned liquid crystal display

2002-06-05

2003-05-27

Kim, Robert H. (Department: 2871)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

C349S122000, C349S123000, C349S129000

Reexamination Certificate

active

06570636

ABSTRACT:

BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a vertically aligned liquid crystal display, and more particularly, to a vertically aligned liquid crystal display having a aperture pattern formed in electrodes to obtain a wide viewing angle.
(b) Description of the Related Art
A liquid crystal display (LCD) is structured having liquid crystal injected between an upper substrate having a common electrode and a color filter, and a lower substrate having thin film transistors and pixel electrodes. A voltage of a different potential is applied to the pixel electrodes and common electrode to form an electric field, thereby varying the alignment of liquid crystal molecules of the liquid crystal material. In this way, the transmittance of incident light is controlled to display images.
In a vertically aligned (VA) LCD, long axes of the liquid crystal molecules align themselves vertically to the substrates in a state where no electric field is formed between the substrates. The VALCD has a high contrast ratio and a wide viewing angle such that this LCD configuration is the most commonly used type of liquid crystal display.
In one method to obtain a wide viewing angle in the VA LCD, aperture patterns are formed in the electrodes. With this configuration, a fringe field is used to uniformly scatter a slanting direction of the liquid crystal molecules into four directions to achieve a wide viewing angle. A conventional VA LCD, having aperture patterns formed in the electrodes to obtain a wide viewing angle, will now be described with reference to FIG.
1
.
FIG. 1
shows a partial sectional view of a conventional VA LCD having aperture patterns formed in electrodes.
A pixel electrode
110
is formed on an insulating lower substrate
100
, and a common electrode
210
is formed on an insulating upper substrate
200
. Aperture patterns are formed in the pixel electrode
110
and the common electrode
210
. Apertures of the aperture pattern of the pixel electrode
110
are provided alternately with apertures of the aperture pattern of the common electrode
210
. Further, liquid crystal material is injected between the substrates
100
and
200
to form a liquid crystal layer
300
.
As shown in the drawing, a fringe field generated by the aperture patterns uniformly controls a slanting direction of liquid crystal molecules of the liquid crystal layer
300
. A wide viewing angle is realized as a result. However, at center portions between apertures of the upper substrate
200
and the lower substrate
100
, weak fringe field forms an area by the vertical electric field with respect to the substrates where the liquid crystal molecules do not quickly change alignments by the electrical field. Also, the liquid crystal molecules in these areas begin to slant only after liquid crystal molecules in the vicinity of the aperture patterns are slanted. This slows down the response speed of the LCD.
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 vertically aligned liquid crystal display in which a lower and an upper aperture pattern are formed in electrodes of at least one substrate to form a stepped pattern at the center of the aperture pattern. Accordingly, a response speed is improved.
To achieve the above object, the present invention provides a liquid crystal display comprising a first substrate made of an insulating material; pixel electrodes formed on the first substrate, the pixel electrodes having a first aperture pattern; a second substrate made of an insulating material and provided opposing the first substrate at a predetermined distance; a common electrode formed on the second substrate, the common electrode having a second aperture pattern; and a liquid crystal layer made of liquid crystal material injected between the first substrate and the second substrate, wherein either or both of the pixel electrodes and the common electrode include stepped portions, which protrude a predetermined distance away from the substrates, between apertures of the first and/or second aperture pattern.
According to a feature of the present invention, the pixel electrodes include the stepped portions.
According to another feature of the present invention, the stepped portions are formed by providing the pixel electrodes over a gate insulation layer and a protection layer.
According to yet another feature of the present invention, the common electrode includes the stepped portions.
According to still yet another feature of the present invention, the pixel electrodes include first stepped portions and the common electrode includes second stepped portions.
According to still yet another feature of the present invention, the first stepped portions and the second stepped portions are provided in a sequence of the first aperture pattern, the second stepped portions, the first stepped portions, and the second aperture pattern.
According to still yet another feature of the present invention, the liquid crystal display further comprises thin film transistors formed on the first substrate, the thin film transistors switching image signals transmitted to the pixel electrodes.


REFERENCES:
patent: 6081315 (2000-06-01), Matsuyama et al.
patent: 6100953 (2000-08-01), Kim et al.
patent: 6424396 (2002-07-01), Kim et al.

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