No abstract

No abstract

No abstract

A new class of compounds suitable for LCD applications has have synthesized, incorporating a tri uoromethyl group in the terminal alkoxy or alkenyloxy chain. These compounds ful l many of the speci cations for use in TN-LCDs. Compounds containing several aromatic rings were synthesized with a view to producing compounds of high birefringence. This aspect also included the synthesis of compounds containing a carbon-carbon triple bond. Materials with three phenyl rings were also prepared in an attempt to produce nematic liquid crystals with a high clearing point and a high birefringence. Molecules containing a lateral uoro substituent were synthesized in order to generate a high positive value of the dielectric anisotropy, a low melting point and no smectic mesophases. A series of compounds incorporating a carbon-carbon double bond was prepared in an attempt to produce compounds with a high nematic clearing point and a high birefringence. Introductionto be used. Since both the switch-on and switch-oOEtimes Most commercially available liquid crystal displays are directly proportional to the square of the cell gap, a (LCDs) with high information content utilize the twisted high birefringence can also give rise to short switching nematic eOE ect (TN-LCDs) [1][2][3][4][5][6][7][8][9][10][11][12] or in-plane switching times. The nematic mixtures used in LCDs with active (IPS-LCDs) [13-16] with active matrix addressing. matrix addressing should also exhibit a very high initial These electro-optical eOE ects using nematic liquid crystals value for the resistivity, which should stay as constant can be used to produce large area, light, at panel displays as possible over the life-time of the display, in order to with a high contrast ratio, grey scale (full colour), fast maintain the optical performance. A high value for the response times, wide operating temperatures and almost holding ratio (HR) indicates that the resistivity of the complete absence of cross-talk. The active element at liquid crystal is stable over time. each individual pixel may be a discrete thin lm tranNematic liquid crystals containing several halogen sistor (TFT) [6] or metal-insulator-metal diode (MIM) atoms, especially uorine atoms were found to exhibit [7] on an amorphou s or crystalline silicon substrat e [8]. a stable holding ratio and an acceptable high value The TN-LCD requires nematic liquid crystals of high of the dielectric anisotropy [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. The value for the positive dielectric anisotropy in order to produce a low permanent dipole moments of several carbon-uorine threshold voltage and short response times. Furthermore, bonds were found to be additive, which results in a high they should exhibit a low viscosity and appropriate value for the dielectric anisotropy. This does not lead values of the elastic constants (especially k 11 and k 33 ) to the solvation of ions from the alignment layers, as in order to reduce the response times further. A wide happens for nematic mixtures of ...