Super-twisted nematic mode

T. Scheffer and J. Nehring, Twisted nematic and super-twisted nematic mode LCDs, in Liquid crystals -applications and uses, Vol. 1, ed. by B. Bahadur (World Scientific, New Jersey, 1990). 

One of the most important necessary conditions in recent LCD such as thin film transistor and super twisted nematic modes is to have higher voltage holding ratio Ry > 95%) even in a high-temperature... 

STN (super twisted nematic) mode T.J. Scheffer, J. Nehring Appl. Phys. Lett. 45, 1021 (1984)... 

In LCDs various LC modes of operation are applied like twisted nematic (TN) [5], super twisted nematic (STN)[6], vertically aligned nematic (VAN) [7,8], optically compensated birefringence (OCB) [9] and in plane switching (IPS) [10-12]. The LC mode used depends on the demands of a specific application, like the viewing angle, power consumption and manufacturing cost. 

As the rate of twist in a liquid crystal cell increases, the ability of the layer to rotate the plane of polarization of light is diminished. The light becomes elliptically rather than linearly polarized, and the major axis of the ellipse is rotated. This is the situation in the liquid crystal cells used for the super-twisted nematic display. Such displays are therefore normally operated in a variable birefringence mode [25]. In order to allow for the optical rotatory power of the liquid crystal layer, special choices of the optical thickness of the layer and the angles at which the polarizing filters are set allow efficient... 

Table 4.1 summarizes which type of the LC film series is compatible for each LCD mode. Twisted oriented films can be used for color compensation of STN (super twisted nematic)-LCDs [36], in particular for color STN-LCDs in mobile devices. Because such color mobile STN-LCDs use only one polarizer, it is necessary that the combination of the compensation film and STN cell functions as a wideband A/4 plate. Multiple films are required in order to achieve this condition for usual, stretched films, but by using the twisted oriented film this can be realized by just one film [37-39]. 

The super birefringent effect (SBE-LCD) reported by Scheffer and Nehring from Brown Boveri in Baden, Switzerland, uses the optical interference of two normal, elliptically polarised modes of transmitted light generated by a high-tilt, highly-twisted nematic structure viewed between two polarisers set in an unusual way, i.e. the input polarisation direction is not parallel to the nematic director at either substrate surface and the polarisers are not crossed at 90°, see Figure 3.10. 

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