Central to the technology behind twisted nematic or TN display panel is the use of nematic liquid crystal sandwiched between two plates of glass substrates coated with transparent indium-tin-oxide or ITO. This ITO surface are further coated with alignment layers that both rub in one direction.
The rubbing orients the liquid crystal molecules parallel to the rubbing direction. Because the rubbing directions on the two glass substrates are perpendicular to each other, a 90-degree twist of director from one glass substrate to the other is formed inside the cell.
Manipulation of polarised light is the underlying technological principle behind TN display. When light enters the TN cell, the polarisation state twists with the director of the liquid crystal material.
TN display panel is currently the most common type of liquid crystal display used in popular consumer electronic devices such as watches and calculators. This display technology was in fact universal in portable electronics during the 1990s.
Further demands for better and wider display applications however resulted in the emergence of newer display technologies. It is important to take note that twisted nematic display technology cannot respond to these demands because of its inherent limitations.
Nonetheless, it cannot be denied that the introduction of this display in 1970s was one of the main technological breakthroughs because it commercialised the use of LCD and made the use of display technology in consumer electronic devices affordable and practical.