Transient Current of Nematic Liquid Crystals with Negative Dielectric Anisotropy Induced by Step-Voltage Excitation

Measurement of viscosities from the transient current of nematic liquid crystals with negative dielectric anisotropy

“…We have applied these equations to the problem of one-dimensional distortion of the director in a homeotropic NLC cell along the z-axis, which is perpendicular to the electrode surfaces of the NLC cells and is in the direction of an applied electric field [2]. The NLC slab is confined between two parallel …”

“…The director orientation at the electrodes is rigidly fixed (θ = θ o ), reflecting the strong anchoring condition, where θ o is the pretilt angle. We have shown in our previous paper [2] that the appropriate boundary condition for fluid flow on the fieldinduced director response in homeotropic NLC cells with Δε b 0 is the free-slip boundary condition, which means that NLC molecules move freely on the electrode surface and which corresponds to σ(t) = 0 in Eq. (1).…”

“…We have shown that the flow effects and the free-slip boundary condition for fluid flow play a key role in eliciting a faster electrooptic response in VA-NLC displays by analyzing the transient currents, induced by step voltage application, in homeotropic NLC cells with negative dielectric anisotropy (Δε b 0, where Δε = ε // − ε ⊥ is the dielectric anisotropy of NLCs, ε // and ε ⊥ being the dielectric constants parallel and normal to the director, respectively) [2]. In VA-NLC displays, NLC materials with Δε b 0 are used.…”

Optimization of liquid crystals for television

“…2 Recent results demonstrate, in addition, the importance of the flow effect. 3 Low viscosity is the key material parameter for TV application. Each pixel in a display is driven by a TFT charging the pixels by signal pulses.…”

Effects of Fluid Flow on Electric-Field-Induced Director Reorientation in Homogeneous and Homeotropic Nematic Liquid Crystal Cells, Probed by Transient Current Measurements

“…For this reason, there has been a substantial amount of research on the interaction between the director orientation and fluid flow in NLC cells. [1][2][3][4][5][6][7][8][9] We have investigated the field-induced director orientation in NLCs by analyzing the transient currents in NLC cells excited by a dc step voltage pulse. [9][10][11][12][13] The transient currents in homogeneous and twisted NLC cells with positive dielectric anisotropy (Á > 0) have been successfully explained by the dynamic theory of NLCs in which the flow effects are neglected.…”