Liquid crystal display having wide viewing angle

Details Liquid crystal display having wide viewing angle Liquid crystal display having wide viewing angle

1998-05-29

2001-09-04

Sikes, William L. (Department: 2871)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

C349S144000, C349S038000, C349S129000

Reexamination Certificate

active

06285431

ABSTRACT:

BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a liquid crystal display having wide viewing angle.
(b) Description of the Related Art
A liquid crystal display (LCD) includes two substrates and a liquid crystal layer interposed therebetween. The transmittance of the light is controlled by the strength of the electric field applied to the liquid crystal layer.
A conventional twisted nematic (TN) liquid crystal display, which is one of the most widely used LCD, has a couple of transparent substrates which have transparent electrodes respectively on their inner surfaces, a liquid crystal layer between two substrates, and a couple of polarizers which are attached to the outer surfaces of the substrates respectively. In off state of the LCD, i.e., in the state that the electric field is not applied to the electrodes, the long axes of the liquid crystal molecules are parallel to the substrates and twisted spirally with a constant pitch from the inner surface of one substrate to that of the other substrate, and thus the orientation of the long axes of the liquid crystal molecules vary continuously.
However, the contrast ratio of the conventional TN LCD in a normally black mode may not be so high because the incident light is not fully blocked in its off state, i.e., in absence of the electric field.
To solve this problem, a vertically aligned twisted nematic (VATN) mode LCD is proposed in the U.S. Pat. No. 3,914,022 and in “Eurodisplay '93”, pp. 158-159 by Takahashi.
The VATN in normally black mode may have an off state which is sufficiently dark, because the liquid crystal molecules are aligned perpendicular to the substrates in off state. However, the viewing angle of the VATN LCD may not be so wide.
On the other hand, T. Yamamoto et al. disclosed a VATN simple matrix LCD using fringe fields in “SID '91, pp. 762-765”, and Lien proposed a structure having an aperture in the pixel electrode to solve the problem of low transmittance in on state of a simple matrix multi domain VATN.
However, the structure that Lien proposed, may have light leakage generated near the aperture.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to widen the viewing angle of LCD.
It is another object of the present invention to prevent the disclination of LCD.
These and other objects, features, and advantages are provided, according to the present invention, by a liquid crystal,display comprising a first substrate having a common electrode, a second substrate having a pixel electrode and a storage capacitor electrode. One of the electrodes has an aperture and the storage capacitor electrode is located at the position corresponding to the aperture.
The storage capacitor electrode prevents the light leakage due to a fringe field generated from the aperture.
Between the first and the second substrates, a liquid crystal layer having negative dielectric anisotropy may be interposed. The liquid crystal layer may include chiral nematic liquid crystal or nematic liquid crystal having chiral dopant of 0.01-3.0 wt %.
Two substrates may have alignment layers respectively, to align the molecular axes of the liquid crystal molecules perpendicular to the substrates. The alignment layers may be rubbed or not.
The storage capacitor electrode may be connected to a gate line and the number of the storage capacitor electrode may be more than one.
It is preferable that the width of the aperture is 3-15 &mgr;m and the distance between the apertures is 8-50 &mgr;m.
To obtain the wide viewing angle, the linear apertures in adjacent pixel regions extend in the different directions. For example, if the direction of the aperture of one pixel is parallel to the gate line, the aperture of the adjacent pixel is preferably perpendicular to the gate line. As a result, the liquid crystal molecules rotate in 4 directions.


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