Zhidong Zhang

Optimal rubbing angle for reflective in-plane-switching liquid crystal displays

Rubbing angle effects on the response time and optical threshold voltage of the reflective in-plane-switching homogeneous liquid crystal displays were analyzed. As the rubbing angle increases, the rise time decreases except that its operating voltage also increases. The optimal rubbing angle is around 30°–40°.

Pretilt angle effects on critical voltage and dynamic response of pi cell

The critical voltage with an arbitrary pretilt angle is given analytically which is consistent with the numerical results [Acosta et al., Liq. Cryst. 27, 977 (2000)]. The author’s results show that the critical voltage is dependent on the parameters of liquid crystal and pretilt angle but is independent of the cell gap. By numerical simulation the authors find that the on time of pi cell decreases with the increasing pretilt at the same voltage, and the off time of the cell driven by the undershoot method is much faster than that of the normal driven method for the cell with nonzero critical voltage.

Random laser emission in a sphere-phase liquid crystal

We investigated random lasing from a fluid self-assembly sphere-phase liquid crystal, which was composed of three-dimensional twist sphere structures with disclinations among them. The threshold energy of the random lasing from sphere-phase liquid crystal was 32% of that from the chiral nematic phase because of the interference associated with multiple scattering by randomly distributed sphere-phase platelets. Such random lasers composed of self-assembly soft organic materials may be useful for holographic displays, point-of-care biomedical analysis, and optical security coatings.

Reflective liquid-crystal display using an in-plane-switching super-twisted nematic cell

Two in-plane-switching (IPS) super-twisted nematic (STN) cells are proposed for reflective liquid-crystal displays. The IPS 180°-STN cell exhibits a normally black display with a relatively low-operating voltage, fast response time, and wide viewing angle. Potential applications for large screen reflective displays are foreseeable.

Reflective in-plane switching liquid crystal displays

The performance of a reflective in-plane switching (IPS) liquid crystal display is simulated by the parameter space method. The IPS electrodes and reflectors can be separately fabricated on the top and bottom substrates. The normally black reflective in-plane switching display shows wide viewing angle, high contrast ratio, weak color dispersion, and fast response time.

Twist angle effects on the dynamic response of in-plane-switching liquid crystal displays

Twist angle effects on the response time of in-plane-switching liquid crystal displays are analyzed. The authors propose a device configuration whose top and bottom boundary liquid crystal layers are symmetric to each other with respect to the electric field direction. The analytical results of this device configuration indicate that the response time is improved at least four times faster than that of a conventional in-plane-switching twisted-nematic mode and normal in-plane-switching mode.

Flexoelectric Effect in a HAN-IPS Cell

Flexoelectric properties are evident in experiments preformed with hybrid aligned nematic. In this article, the flexoelectric effect in a hybrid aligned nematic in-plane switching liquid-crystal cell is investigated. The equations for the distribution of the liquid-crystal director and the expression of critical voltage in the one-constant approximation are obtained. The results of computer simulation show that the value of angle φ exceeds 90 degrees and closes to 180 degrees between the bottom substrate and the mid-layer.

Rapid response mechanism of pi cell

The rapid response mechanism of pi cell is investigated in detail using one elastic constant and small angle approximation. The improving times of the decay time for pi cell driven by undershoot and normal method compared with that for a Freedericksz cell are calculated and it decreases with the increasing driven voltage for the undershoot method but is larger than that for the normal method. The author’s results show that the same gray-to-gray response times can be obtained using undershoot method but cannot using normal method.

Critical voltage of π-cell liquid crystal displays

The critical voltage is investigated theoretically for π-cell with arbitrary pretilt angle. Our results show that the analytical critical voltage decreases as the pretilt angle increases, which is consistent with the numerical and experimental data. We also find that the critical voltage is dependent on the pretilt angle and the splay and bend elastic parameters of liquid crystal material, but independent on the cell gap.

Influence of rubbing-alignment on microwave modulation induced by liquid crystal

The microwave modulation induced by liquid crystal is decided by the liquid crystal director distribution under an external applied voltage. The rubbing-alignment of substrate has an effect on the liquid crystal director, which must result in the change of microwave phase-shift. To illustrate the influence of rubbing-alignment on the microwave phase-shift, the microwave modulation property of twisted nematic liquid crystal is researched adopting the elastic theory of liquid crystal and the finite-difference iterative method. The variations of microwave phase-shift per unit-length for different pre-tilt and pre-twist angles of liquid crystal on the substrate surface and anchoring energy strengths with the applied voltage are numerically simulated. The result indicates that with the increase of pre-tilt angle and with the decrease of anchoring energy strength the weak anchoring twisted cell with pre-twisted angle 90° relative to the strong anchoring non-twisted cell can increase the microwave phase-shift pe...