Electrically controlled director slippage over a photosensitive aligning surface; in-plane sliding mode

Abstract

We have studied the electro-optical characteristics of a homogeneously aligned nematic liquid crystal (LC) with weak planar anchoring of the director at the bounding substrates. By using the in-plane switching (IPS) of the LC which is achieved by an in-plane electric eld, the driving voltage was con rmed to be far less than that of the conventional IPS mode in which both substrates possess strong anchoring characteristics. Moreover, because of the absence of strong subsurface director deformations, the cell could operate optically in the Mauguin regime. Using these features we propose a new type of LC switching mode-in-plane sliding (IPSL) mode. We have realized this mode in a LC cell comprising one reference substrate with strong director anchoring and one substrate covered with photoaligning material with weak anchoring. In order to clarify the switching process, we derived a simpli ed expression for the threshold voltage on the assumption of uniformity of the in-plane electric eld. For the dynamical response of the LC to the in-plane electric eld, the switching on and o relaxation times of the IPSL mode were found to be longer than for the traditional IPS mode. However, we have proposed an optimized cell geometry for the IPSL mode with a response time comparable to that of the IPS mode.

Reducing driving voltage and securing electro-optic reliability of in-plane switching liquid crystal display by applying polysulfone photoalignment layer with photo-reactive mesogens

“…In consideration of different anchoring forces, the response times of three cases are not only dependent on d, γ and K 22 , but also related to the surface anchoring energy (W). Therefore, the modified rising and decaying times have been shown in the following forms [12][13][14]:…”

“…For IPS LC cell in consideration of cell surface boundary condition, the implicit dependence of threshold voltage (V th ) and anchoring energy (W) is given by [13] …”

“…Since the non-contact LC photoalignment does not induce the electrostatic charge and the undesired mechanical damage leading to degradation of LCD quality, this technology has attracted a lot of scientists and engineers for the LCD application. Despite the high application potential of photoalignment for LCD, it results in weak anchoring with NLCs compared with its rubbing-alignment counterpart, [11][12][13][14] which increases the driving voltage and decelerates response time of IPS LCD. Additionally, weak anchoring interactions between alignment layer and NLCs cause the insufficient LC alignment stability as well as the pronounced image sticking effect.…”

Liquid‐crystal photoaligning by azo dyes (Invited Paper)

“…Usually, the azimuthal anchoring energy of photoaligning materials is rather small (about 1-7 × 10 -6 J/m 2 ), which is about an order of magnitude smaller than the value obtained by the rubbing method. [11][12][13][14] The azimuthal anchoring energy W ϕ of a photoaligned substrate was measured. 15 It was found that the anchoring energy was very high and >10 -4 J/m 2 , which is the same as the anchoring energy of the rubbed polyimide (PI) layer.…”

Electrically Controllable Liquid Crystal Component for Efficient Light Steering

“…For example, a weak LC alignment is known to reduce the operating voltage and increase the response time [27], [28]. In the past decades, several LC alignment techniques were developed to induce uniform liquid crystal orientations [29].…”