Surface stabilized ferroelectric liquid crystals

Surface Stabilized Ferroelectric Liquid Crystals (SSFLC)116 Here all three vectors of spontaneous polarization (Fs) are initially aligned by surface effects in thin cells (ca 2 pm). The switchability is due to 180° rotation of the Fs vectors on a cone. 

In a chiral smectic (Sc ) phase, the tilt angle is the same within a layer, but the tilt direction processes and traces a helical path through a stack of layers (Figure 43). It has been demonstrated that when such a helix is completely unwound, as in a surface stabilized ferroelectric liquid crystal cell, then changing the tilt of the molecules fi om +0 to —0 by alternating the direction of an applied field results in a substantial electro-optic effect, which has the features of veiy fast switching (%1 - lOps), high contrast and bistability [87]. The smectic A phase of chiral molecules may also exhibit an electro-optic effect, this arises due to molecular tilt fluctuations which transition is approached, which are combined with a... 

The backbone affects the dynamic behavior of the ferroelectric liquid crystalline polymer. Sandwiching the two kinds of ferroelectric liquid crystals between two ITO-coated glass plates of 1.5 microns gap respectively, one constructs a SSFLC (surface stabilized ferroelectric liquid crystal) cell. The switch time between two optical states r is determined by... 

Wu, Y., Yuan, B., Zhao, J.-G. Ozaki, Y. (2003). Hybrid Two-Dimensional Correlation and Parallel Factor Studies on the Switching Dynamics of a Surface-stabilized Ferroelectric Liquid Crystal. Journal of Physical Chemistry B, Vol. 107, No. 31, pp. 7706-7715... 

J.Y. Huang, L.S. Li, and M.C. Chen, Probing molecular binding effect from zinc oxide nanocrystal doping in surface-stabilized ferroelectric liquid crystal with two-dimensional infrared correlation technique, J. Phys. Chem. C, 112, 5410-5415 (2008). 

Fig. 5.2 Helical structure of SmC phase (a) and surface stabilized ferroelectric liquid crystals (SSFLC) (b and c)...

Surface-stabilized ferroelectric liquid crystal Splay-twist Supertwisted nematic Transmission electron microscopy Twisted nematic Thin film transistor Uniform lying helix Ultraviolet... 

Figure 4.9 Schematic diagram of the bookshelf cell structure of the surface-stabilized ferroelectric liquid crystal display, (a) The director is along the direction Ai when the applied field is up. (b) The director is along the direction Ai when the applied field is down, (c) Directions of the polarizer and analyzer.

This problem is overcome by Clark and Lagcrwall in their invention of the surface-stabilized ferroelectric liquid crystal (SSFLC) device [16], shown in Figure 4.9. The liquid crystal is sandwiched between two parallel substrates with the cell gap, h, thinner than the helical pitch, P, of the liquid crystal. The inner surface of the substrates is coated with alignment layers which promote parallel (to the substrate) anchoring of the liquid crystal on the surface of the substrate. The smectic layers arc perpendicular to the substrate of the cell, while the helical axis is parallel to the substrate. Now the helical twist is suppressed and unwound by the anchoring. 

As discussed in Chapter 4, surface stabilized ferroelectric liquid crystals (SSFLCs) have two stable states at zero field. The two states have different planar orientational angles as shown in... 

Clark, N. A., and Lagerwall, S. T., Surface-stabilized ferroelectric liquid crystal electro-optics new multistate structures and devices. Ferroelectrics, 59, 25-67 (1984). 

The surface-stabilized ferroelectric liquid crystals in the smectic C (SmC ) phase are among the most interesting types of liquid-crystalline systems because of their potential applications in high-resolution flat panel displays and fast electro-optical devices [73-76]. Within this class of compounds, ferroelectric liquid-crystalline polymers (FLCPs) have gained theoretical and practical interest as systems which combine the properties of polymers and ferroelectric liquid crystals. This combination is achieved by attaching the ferroelectric mesogen to a main chain via a flexible spacer... 

In the sections on smectic liquid crystals, first the alignment and molecular orientation of surface stabilized ferroelectric liquid crystals (SSFLCs) are treated in detail. Next, the alignment technologies needed for the occurrence of bistability are detailed. Furthermore, liquid crystalline devices made of AFLC materials and the applications of FLC and AFLC materials to active matrix devices are discussed. 

At first in this chapter, ferroelectric liquid crystals (FLCs) and their most interesting application as surface stabilized ferroelectric liquid crystals (SSFLCs) are briefly explained. 

Surface-Stabilized Ferroelectric Liquid Crystals (SSFLCs)... 

Charge-controlled phenomena in the surface-stabilized ferroelectric liquid crystal structure. Figure 4, W.J.A.M. Hartmann, Journal of Applied Physics, 66, p. 1132 (1989). Reproduced by permission of American Institute of Physics. 

Effect of alignment layer conductivity on the instability of surface stabilized ferroelectric liquid crystal devices. Figures 1 and 2, TC. Chieu and K.H. Yang, Applied Physics Letters, 56 (14), p. 1326 (1990). Reproduced by permission of the American Institute of Physics. 

So far, four display modes have been proposed in ferroelectric and antiferroelectric display applications, as shown in Figure 9.34. A bistable switching in surface stabilized ferroelectric liquid crystals (SSFLCs) has been manufactured as a passive matrix liquid crystal display (PM-LCD). The counterpart of AFLC is a tristable switching, which is also a promising candidate for PM-LCD. In addition to these PM-LCDs, active matrix displays (AM-LCDs) are also proposed in FLC and AFLC materials, i.e., deformed helix FLCD (DHFLC) and V-shaped LCD (VLCD). In this section, PM-AFLCD and AM-VLCD will be described. 

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