Liquid crystal display is a passive display that cannot emit light, relying on ambient light instead. It displays patterns or characters using only minimal energy. Due to their low power consumption and miniaturization, the liquid crystal materials used in LCDs are organic compounds with dual liquid and solid properties. Their rod-like structures are generally aligned parallelly within the liquid crystal cell but can change their orientation under the influence of an electric field.

For the positive TN-LCD, when no voltage is applied to the electrodes, the LCD is in the "OFF" state, allowing light to pass through the LCD in a white state. When voltage is applied to the electrodes, the LCD is in the "ON" state, with the liquid crystal molecules aligned along the electric field direction. Light cannot pass through the LCD, resulting in a black state. By selectively applying voltage to the electrodes, different patterns can be displayed.

For STN-LCD, the twist angle of the liquid crystal is greater, resulting in better contrast and wider viewing angles. STN-LCD displays are based on the principle of birefringence, with a base color typically of yellow-green and text in blue, forming the yellow-green mode. When using a purple polarizing filter, the base color turns gray, creating the gray mode. With a polarizing filter featuring a compensation film, the base color becomes nearly white, turning STN into the black-and-white mode, or FSTN. When the three modes of polarizing filters are rotated 90°, they become the blue mode, offering improved effects.