(a) Field of the Invention
The present invention relates to a liquid crystal display, and in particular, vertically-aligned liquid crystal display having a pixel region including a plurality of domains for wide viewing angle.
(b) Description of the Related Art
A typical liquid crystal display (LCD) includes an upper panel provided with a common electrode and an array of color filters, a lower panel provided with a plurality of thin film transistors (TFTs) and a plurality of pixel electrodes, and a liquid crystal layer is interposed therebetween. The pixel electrodes and the common electrode are applied with electric voltages and the voltage difference therebetween causes electric field. The variation of the electric field changes the orientations of liquid crystal molecules in the liquid crystal layer and thus the transmittance of light passing through the liquid crystal layer. As a result, the LCD displays desired images by adjusting the voltage difference between the pixel electrodes and the common electrode.
The LCD has a major disadvantage of its narrow viewing angle, and several techniques for increasing the viewing angle have been developed. Among these techniques, the provision of a plurality of cutouts or a plurality of projections on the pixel electrodes and the common electrode opposite each other along with the vertical alignment of the liquid crystal molecules with respect to the upper and the lower panels is promising.
The cutouts provided both at the pixel electrodes and the common electrode give wide viewing angle by generating fringe field to adjust the tilt directions of the liquid crystal molecules.
The provision of the projections both on the pixel electrode and the common electrode distorts the electric field to adjust the tilt directions of the liquid crystal molecules.
The fringe field for adjusting the tilt directions of the liquid crystal molecules to form a plurality of domains is also obtained by providing the cutouts at the pixel electrodes on the lower panel and the projections on the common electrode on the upper panel.
Among these techniques for widening the viewing angle, the provision of the cutouts has problems that an additional mask for patterning the common electrode is required, an overcoat is required for preventing the effect of the pigments of the color filters on the liquid crystal material, and severe disclination is generated near the edges of the patterned electrode. The provision of the projections also has a problem that the manufacturing method is complicated since it is required an additional process step for forming the projections or a modification of a process step. Moreover, the aperture ratio is reduced due to the projections and the cutouts.