Voltage holding ratio

Shortly after the commercial introduction of the first active matrix LCD in 1989 it became clear that cyano-based liquid crystals of the second generation (e.g. 3-6) cannot be used for this application. Even after extensive purification, the voltage holding ratio of this type of material is too low. The stringent reliability requirements could, on the other hand, be easily fulfilled with super-fluorinated materials (SFM), such as those depicted in Scheme 4.11. For this reason - with in-plane switching (IPS) technology as the only exception - only SFM are currently used in AM-LCD. 

Figure 4.11 Relationship between the calculated heat of interaction (gray bars, —AHj in kcal mol ) for different types of liquid crystal and a sparkle (calculated at the AMI level of theory with MOPAC 6.0) and the measured voltage holding ratio (diamonds, VHR in%) [42].

PVPHF poly(vinylpyridine) hydrofluoride VHR voltage holding ratio... 

Table 2.2 Characteristics of alignment materials on the market. VHR, R-DC and a represent Voltage Holding Ratio, Residual DC voltage and refractive index, respectively... 

Voltage holding ratio Flicker Voltage retention ratio for 16 msec after chsirging the electrode for 20 psec. 

Voltage holding ratio in alignment layers for liquid crystal displays... 

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... 

Voltage holding ratio (%) for a variety of wholly and semi-aromatie Pis (reproduced from Ref. [142])... 

Peter Brody et al. [43] at Westinghouse were the first to realize the compatibility of TN-LCDs with thin-film-transistors (TFTs). In 1974 they realized the first TFT-addressed TN-LCD prototype whose negligible current consumptimi (field effect) and therefore large voltage holding ratio [3-5, 30] enables pulse-sequential matrix addressing of its picture elements. TFT addressing circumvented... 

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