Why do in-plane switching LCDs have wider viewing angles?
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-plane switching (IPS) displays achieve wider viewing angles because of how they manipulate liquid crystal molecules compared to traditional twisted nematic (TN) displays.
While standard TN displays operate by applying a voltage that causes molecules to orient perpendicular to the substrate plates, IPS displays function by applying a switching voltage to electrodes located on a single substrate. This configuration causes the liquid crystal molecules to untwist within the plane of the substrate rather than tilting vertically. Because the molecules remain parallel to the screen surface during operation, the optical properties remain more consistent when viewed from various angles, resulting in viewing characteristics that are intrinsically superior to those of standard TN displays.1
While this design provides a wider viewing angle, it requires more complex electrode circuitry on the substrate, which can lead to a less efficient use of the display's backlight.1