Key Engineering Materials Vols. 428-429

Abstract: The lyotropic liquid crystalline behavior of N-Cetyl-N, N, N, Trimethyl Ammonium Bromide (CTAB) with ethylene glycol (EG) has been investigated. These compounds are non-mesogenic in nature and exhibits Sm A, Sm B and Sm G phases. The stability of the phases is investigated using X-ray diffraction and optical studies. The layer thickness and molecular length are calculated using Bragg’s equation. The interfacial area per polar group and average thickness of hydrocarbon layers are estimated for different concentrations of the mixtures at different temperatures.

Abstract: By triangular wave method, the switching currents of an azo-containing banana-shaped antiferroelectric liquid crystal were investigated as a function of temperature. As the temperature increases from 150 to 175oC, the switching currents of the banana-shaped liquid crystal were observed to decrease linearly with the temperature. The unusual temperature-dependent polarization was discussed in the light of Landau-de Gennes theory.

Abstract: The paper reports the methods for making a novel optical device consisted of photo alignment nematic liquid crystal films and polarizers. The color shift of the device depends on not only the viewing angle but also the viewing orientation. The retardation and intensity of the reflected light are theoretically calculated on the basis of Jones Matrix, and a spectral-RGB transition program is introduced to display colorful results directly. The theoretical results show excellent agreement with experimental data. It is an effective method for predicting interference color and optimizing key parameters of the device. The device can be used to protect valuable documents against fraud because of its special optical variable effects which is caused by interference of polarized light.

Abstract: By triangular wave method, we studied the effects of ultraviolet irradiation on the polarization of a binary liquid crystal mixture. The mixture was comprised of 94 wt% of banana-shaped liquid crystal 4-chloro-1,3-phenylene bis [4-(4-n-tetradecyl) phenylimino methyl] benzoate and 6 wt% of an azo-containing rod-shaped liquid crystal hexanoic acid 4-(4-ethoxy-phenylazo)-phenyl ester. Under the 365 nm irradiation for 40 minutes, the polarization of the mixture was observed to decrease 10% although the component of the banana-shaped liquid crystal was photostable. Our results demonstrated that photolysis took place in the component of azo-containing rod-shaped liquid crystal.

Abstract: The surface optical anisotropy of rubbed polyimide films has been detected using reflection anisotropy spectroscopy. The amplitude of the reflection anisotropy signals increases with the rubbing strength. Rubbing also causes changes in pretilt angle of liquid crystal molecules which are in contact with the rubbed polyimide. An increase in rubbing strength results in an increase in the pretilt angel. The pretilt of the liquid crystal molecules was found to linearly correlate with the amplitude of the RA signals.

Abstract: The electronic transitions in a classical banana-shaped liquid crystal 1,3-phenylene-bis [4-(4-octylphenylimino) methyl] benzoate have been investigated by measuring its optical absorption spectra in dilute solutions of ethyl alcohol and by calculating its electronic structures with extended Hückel tight binding program. The banana-shaped compound shows strong absorptions at 240, 280, 350 nm, respectively. On the basis of the calculated electronic structures, the three strong absorptions can be assigned to the *, n*, and nn* electronic transitions in this banana-shaped compound.

Abstract: The effects of cyclic heating and cooling on the banana-phase growth behaviors of the prototype banana-shaped liquid crystal 1,3-phenylene-bis[4-(4-octylphenylimino)methyl]benzoate were investigated with differential scanning calorimetry and polarized optical microscopy, respectively. Cyclic heating and cooling can reduce the phase transition temperatures and increase the domain sizes of the banana phases of the banana-shaped liquid crystal. These results can be interpreted in terms of the nucleation and growth of the banana phases out of its isotropic phase of the banana-shaped liquid crystal.

Abstract: As we know, we normally used stacked aluminum bus line as the Gate or Source/Drain layer in LCD now, but the next general LCD needs larger display area, higher resolution, and faster response time, so we need develop the new TFT bus line structure and select the appropriate metallization materials to decrease the resistance of bus line. There are many new kinds of structure and material were used, for example copper, silver and their alloys, pure copper have some advantages among them because of its low electric resistance and cost, but it is restricted by the problem of pure copper’s lifting and etching. In this paper, we not only use electroless copper plating to decrease the resistance and cost of bus line but also use the half-buried structure to increase the thickness of bus line, it can combine these two new technologies well in LCD. We use the half-buried structure copper bus line to make some panel samples, it can decrease the delay of RC greatly (it is lower than 1/4 of normal aluminum bus line panel in the same size).

Abstract: There is a desire for a display technology which can change the display viewing angle. Controllable Viewing Angle (CVA) device has been developed by using a Guest-Host liquid crystal cell which allows a high light-shielding effect and the control with a wide range of available viewing angle. By putting the CVA device on a Thin-Film Transistor ( TFT ) Liquid-Crystal Panel, or placing a Guest-Host Liquid Crystal (GHLC) device between the LED and the backlight, we have realized a simple controllable viewing-angle LCD which could be switched in the narrow and normal(wide) viewing angle. The viewing angle can decrease to 40° when power is on but it also can shift to normal viewing angle when power is off.

Abstract: The pigment electrophoresis dispersion has been the widely used system. It is, however, worth of attention if molecular dye, instead of pigment, can be used in the display of electronic paper. By carefully selecting the structure of dyes, especially the metal complex dyes, and studying the properties of the prototype display. It was found there are about 15 dyes electrophoresis and some dyes display well. The dyes ink with good stability during electrophoresis when the electrode was protected, while the response time is about 300 ms, and the concentration is an important factor on the display optic density. The displaying principle of dye ink was studied too.