Twisted Nematic(TN) LCD – In a quiescent state, display has a 90° twist in the alignment of the liquid crystal molecules at the transition between the surfaces of the two glass substrates. Polarizers attached to the outer surface of the substrates are oriented to allow light to pass through the display. When activated selectively by an electric field, the activated segments align to the field and no longer twist light passing through the display creating a contrast between on and off states.

High Performance Twisted Nematic LCD (HTN) – This display has a higher twist (between that of TN & STN) giving it increased performance over TN LCD. The viewing angle is superior to TN and has improved contrast when multiplexing from 1/8 to 1/32 MUX. HTN has a slight yellow tint that looks good with high contrast segments. HTN has a lower cost than STN.

Supertwist Nematic LCD (STN) – The structure of STN is similar to TN & HTN but with 180 to 270 twist. The higher twist gives better contrast and viewing angle for highly mutiplexed applications. STN LCDs normally has a yellow-green or grey background that is due to the optical effect called birefringence that changes the polarization to elliptical rather than linear polarization.

Film Compensated Supertwist Nematic LCD (FSTN) – This display uses an optical retarder to eliminate elliptical polarization from STN display. It has removes the birefringence effects and results in a black and white display. FSTN has the highest contrast and viewing angle for high multiplexed LCD’s.