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SSFLCs

When suitably doped, MBF can form a surface-stabilised-ferroelectric smectic-C (SSFLC) structure. Using simple assumptions regarding core orientations, Binger and Hanna are able to place an upper limit on the SSFLC cone angle for MBF of 30°. [Pg.54]

Along with the prediction and discovery of a macroscopic dipole in the SmC phase and the invention of ferroelectric liquid crystals in the SSFLC system, the discovery of antiferroelectric liquid crystals stands as a key milestone in chiral smectic LC science. Antiferroelectric switching (see below) was first reported for unichiral 4-[(l-methylheptyloxy)carbonyl]phenyl-4/-octyloxy-4-biphenyl carboxylate [MHPOBC, (3)],16 with structure and phase sequence... [Pg.470]

Figure 8.8 Structure and phase sequence of (R)-MHPOBC is shown. One of most famous smectic LCs, antiferroelectric switching in SSFLC cells was first discovered with this material. Figure 8.8 Structure and phase sequence of (R)-MHPOBC is shown. One of most famous smectic LCs, antiferroelectric switching in SSFLC cells was first discovered with this material.
Figure 8.34 Left Gold focal conics of MHOBOW coexisting with accordion domains in 4-p.m SSFLC cell. Cell has not seen electric field. Right Same area after brief application of field above threshold for causing textural change of focal conics from gold SmA-like to bistable blue SmC -like. Transition from gold to bistable blue is still incomplete in this photomicrograph clear domain walls between two textures are easily seen. Figure 8.34 Left Gold focal conics of MHOBOW coexisting with accordion domains in 4-p.m SSFLC cell. Cell has not seen electric field. Right Same area after brief application of field above threshold for causing textural change of focal conics from gold SmA-like to bistable blue SmC -like. Transition from gold to bistable blue is still incomplete in this photomicrograph clear domain walls between two textures are easily seen.
Figure 8.37 Ferroelectric switching and lack of brush rotation illustrated for SiiiCaPf phase exhibited by KYOBOW in SSFLC cell. Figure 8.37 Ferroelectric switching and lack of brush rotation illustrated for SiiiCaPf phase exhibited by KYOBOW in SSFLC cell.
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. [Pg.458]

Electroclinic effect118,119 Close to the phase transition from the tilted SmC phase to the orthogonal SmA phase the tilt angle becomes soft (soft mode). Consequently, one can realize faster switching times than in SSFLC and DHF cells. [Pg.459]

The advantages of SSFLC devices derive to a large extent from the spontaneous macroscopic polarization P of the phase. For example the electrooptic rise time of a prototypical SSFLC light valve is inversely proportional to the magnitude of the polarization. In order to design new FLC materials with large P in a directed way, we... [Pg.484]

Figure 1. The geometry of a parallel-aligned SSFLC cell. Note that the spacing between the glass bounding plates (= 1.5 pm) and the smectic layer spacing (= 35 A) are not to scale. Figure 1. The geometry of a parallel-aligned SSFLC cell. Note that the spacing between the glass bounding plates (= 1.5 pm) and the smectic layer spacing (= 35 A) are not to scale.
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... [Pg.346]

Scherwsky et al. (1989) first utilized a SSFLC display in terms of the ferroelectric liquid crystalline polymer. The polymer SSFLC display is fabricated on the ITO-coated plastic substrate. The display was 15 x 40 cm2 in area and had 100 x 300 pixels (Lagerwell, 1993). The display doesn t need the orientation layer which is essential in the conventional liquid crystal displays in order to anchor the liquid crystal molecules. By lightly bending the... [Pg.349]

Fig. 5.10.9. The SSFLC cell The bookshelf geometry of a thin film of smectic C sandwiched between two glass plates (a) field up (normal to the plane of the diagram) and (b) field down . Fig. 5.10.9. The SSFLC cell The bookshelf geometry of a thin film of smectic C sandwiched between two glass plates (a) field up (normal to the plane of the diagram) and (b) field down .
Another phenomenon that has potential applications is the field-induced tilt or the electroclinic effect. Unlike the SSFLC device, this effect does not possess bistability but it has a faster (submicrosecond) response. By using the same bookshelf geometry and a suitable polarizer and retarder arrangement, the electroclinic effect can be used for modulating a light signal with a transmitted intensity linearly proportional to the applied voltage or as a tunable colour filter. [Pg.387]

It can be seen clearly from Fig. 15 that MSFLC cells offer many advantages. For example, a large gap of 10 Xm can be used [109, 130] instead of 2 pm used in SSFLC cells [131]. The polymeric nature of the LC materials offers excellent shock resistance and mechanical stability. No rubbing of the substrate is needed. We believe that practically useful electro-optical cells can be made utilizing this concept if the FLC-coil diblock copolymers are properly designed, synthesized, and processed. [Pg.89]

Fig. 5.2 Helical structure of SmC phase (a) and surface stabilized ferroelectric liquid crystals (SSFLC) (b and c)... Fig. 5.2 Helical structure of SmC phase (a) and surface stabilized ferroelectric liquid crystals (SSFLC) (b and c)...
Similar to the phase transition from nematic to isotropic phase induced by azobenzene molecules, the trans-cis isomerization also destabilize the SmC phase composed of calamitic mesogens and lower the Curie point, which is a transition temperature where the SmC will transform from ferroelectric to non-ferroelectric. Some examples have been reported with an early demonstration by Ikeda et al. [130-135]. For example, a photoresponsive SmC was formulated by doping 3 mol % of 4,4 -disubstituted azobenzene 29 into a FLC host 27 and the UV irradiation at 260 nm resulted in the lowering of Curie point and the coercive force Ec required to switch the SSFLC due to the destabilization of bent shape cis isomers [130] (Fig. 5.23). When the electric field was close to Ec before irradiation, the flip of polarization of SmC was achieved. It is noteworthy that its response time 500 ps is much faster than normally observed for photochemical N-I phase transitions [131]. [Pg.160]

We can answer the last question if consider a constraction of the so-called surface stabilised ferroelectric liquid crystal cell or simply SSFLC ceU [9]. Such SSFLC cell is only few micrometers thin and, due to anchoring of the director at the surfaces, the intrinsic helical stmcture of the SmC is unwound by boundaries but a high value of the spontaneous polarisation is conserved. The cell is con-stracted in a way to realise two stable states of the smectic C liquid crystal using its interaction with the surfaces of electrodes, see Fig. 13.6a. First of all, in the SSFLC cell, the so-called bookshelf geometry is assumed the smectic layers are vertical (like books) with their normal h parallel the z-axis. Then the director is free to rotate along the conical surface about the h axis as shown in Fig. 13.6b (Goldstone mode). It is important that, to have a bistability, the director should be properly... [Pg.390]

Fig. 13.6 SSFLC cell. The structure of the cell with bookshelf alignment of smectic layers (a) and the cone of the director n motion with two stable states 3 in the electrode plane yz (b). Note that in sketch (a) the director in the cell plane yz is turned to the reader through angle + (shown by thicker right parts of the rod-like molecules) in agreement with sketch (b). The double-head arrow shows the optimum angular position of polarizer P... Fig. 13.6 SSFLC cell. The structure of the cell with bookshelf alignment of smectic layers (a) and the cone of the director n motion with two stable states 3 in the electrode plane yz (b). Note that in sketch (a) the director in the cell plane yz is turned to the reader through angle + (shown by thicker right parts of the rod-like molecules) in agreement with sketch (b). The double-head arrow shows the optimum angular position of polarizer P...
We can use Eqs. (13.13) and (13.14) and find parameters a, %j and p in the SmA phase. For this we need slow, automatically made temperature scans through the A —> C phase transition with simultaneous measurements of SSFLC cell capacitance, i.e. Xsm(T) and the electrooptical response i.e., field induced angle 9(7 at frequency 0.1-1 kHz. Then the asymptotic behaviour of capacitance at temperature T > provides us the value of dielectric constant and susceptibility Xx = (e - and the ratio XsJ c = PX us the coupling constant p in... [Pg.397]

The switching of the director in the surface stabilised ferroelectric liquid crystal cells (SSFLC) [8] has briefly been discussed in Section 13.1.2. Due to its importance for ferroelectric liquid crystal displays we shall discuss this effect in more detail. The geometry of a planar cell of thickness d is shown in Fig. 13.1.2. Now, the helical structure is considered to be unwound. We are interested in the field and time behaviour of the director or c-director given by angle cp(r), and this process is considered to be independent of z and y- coordinates. The smectic C equilibrium tilt angle 9 is assumed constant. [Pg.403]

Fig. 13.12 Clark-Lagerwall effect in thin SSFLC cell. Application of the electric field E between the ITO electrodes causes up-down switching of spontaneous polarization accompanied by conical motion of the director n. The projection of the n-vector on plane xy is C-director forming an angle

Fig. 13.12 Clark-Lagerwall effect in thin SSFLC cell. Application of the electric field E between the ITO electrodes causes up-down switching of spontaneous polarization accompanied by conical motion of the director n. The projection of the n-vector on plane xy is C-director forming an angle <p with respect to y. 9 is the tilt angle between n and the smectic layer normal z...

See other pages where SSFLCs is mentioned: [Pg.2563]    [Pg.2564]    [Pg.468]    [Pg.472]    [Pg.473]    [Pg.498]    [Pg.507]    [Pg.512]    [Pg.466]    [Pg.484]    [Pg.484]    [Pg.485]    [Pg.486]    [Pg.486]    [Pg.490]    [Pg.2563]    [Pg.2564]    [Pg.387]    [Pg.387]    [Pg.139]    [Pg.231]    [Pg.240]    [Pg.270]    [Pg.391]    [Pg.392]    [Pg.403]    [Pg.407]   


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