Why do LCD electrodes need to be electrically conductive and transparent?
In nematic arrangements the crystals are randomly positioned with all their long axes pointing in essentially the same direction, given by a vector known as the director. In smectic arrangements the crystals are further constrained to parallel planes; in smectic A the director is perpendicular to these planes, while in smectic C the director is at some other angle to the planes.
In a liquid crystal display, electrodes must be both electrically conductive and optically transparent to function effectively as part of the display assembly.
The electrodes are required to be electrically conductive to apply an electric field across the liquid crystal layer. This field forces the liquid crystal molecules to reorient, which changes how light passes through the cell and allows the display to create images by switching pixels between light and dark states.123
They must be optically transparent so that they do not obstruct the light passing through the display. Because the electrodes are positioned in the path of the light, they must allow illumination to travel through the assembly to reach the viewer.12
To achieve this combination of properties, manufacturers typically use indium tin oxide (ITO). ITO is an outstanding electronic conductor that maintains high optical transparency due to its specific band gap and electron concentration, making it the standard material for these thin-film electrodes.4