The demands for a power-saving mode for displaying static images are ubiquitous not only in portable devices but also in price tags and advertising panels. At a low-frequency driving in liquid crystal displays (LCDs) for low-power consumption, the flexoelectric effect arises even in calamitic liquid crystals and the optical appearance of this physical phenomenon is found to be unusually large, being noticed as an image-flickering. Although the inherent integrated optical transmittance of in-plane switching (IPS) mode is relatively lower than that of fringe-field switching (FFS) mode, the IPS mode shows no static image-flickering but an optical spike (the so-called optical bounce), at the transient moment between signal positive and negative frames. Here, we demonstrate an IPS mode using negative dielectric anisotropy of liquid crystals (Δε < 0) and fine-patterned electrodes (the width w of and the space l between electrodes ≤ 3 μm) with reduced operation voltage (up to 40.7% to a conventional FFS mode with Δε < 0), reduced optical bounce (up to 4.4%. to a conventional FFS mode with Δε < 0) and enhanced transmittance (up to 32.1% to a conventional IPS mode with Δε > 0). We believe the result will contribute not only to the scientific understanding of the optical appearance of flexoelectric effect but also pave the way for engineering of a superior low-power consumption LCD.

for the additional power reduction in the liquid crystal driving scheme, for example, by reducing the driving frequency f. Displaying smooth and dynamic motion at high-frame rate has been an unquestionable direction to improve the performance of displays, but static images are also becoming significantly important as the application of displays diverges. Thus, as the f is in linear dependence on the power consumption of a module, low-f driving LCD is desired.In driving scheme of LCDs, some amount of electromagnetic radiant energy from the backlight is cut off by the combination of crossed polarizers and liquid crystalline medium while modulating polarization. In terms of energy loss in a liquid crystal layer, therefore, maximizing transmittance is an important factor to improve for better electro-optic performance. From this perspective, achieving both high optical transmittance and low-f driving would be a remarkable breakthrough in terms of power savings.There are two main streams of the initially homogeneous aligned light modulating mode in LCDs: fringe-field switching (FFS) and in-plane switching (IPS) modes. Both modes have a patterned electrode on the one side of two sandwiched substrates. In the IPS mode, patterned pixel (signal-swung) and common electrodes are interdigitated such that symmetrical lateral fields, which have the same translational periodicity with the electrode patterns, are formed between these two electrodes to rotating the liquid crystal director in plane; thus, reorientation occurs only in between the electrodes. In the FFS mode, on the other hand, a plain common electrode and a patterned pixel electrode are not on the same layer and separated by an insulation layer. With this structure, the electric fields form nonsymmetrical fringe shape and the field periodicity is half of the pitch of the electrode patterns. Thus, the rotation of the liquid crystal director takes place over the entire electrode area, which contributes more to the optical transmittance. [4,5] The FFS mode has been dominating the LCD market, especially in portable devices owing to the high aperture ratio, high transmittance, low operation voltage, wide-viewing angle, and touchscreen tolerance. [4,6] Consequently, intensive efforts to reduce the power consumption of this mode have been attempted by using the low-f driving when static images are being displayed. However, severe issues regarding image quality arise in the low-f driving, including image-flickering owing to flexoelectric effect. [7][8][9][10][11][12][13][14] The flexoelectric effect is a An advantageous factor for the technology of displays is low power consumption. For power-saving, low-frequency driving of liquid crystal displays (LCDs) is useful. However, an unacceptable performance drop, from image-flickering, occurs due to occurrence of the flexoelectric effect. Here, based on close agreement between experimental and simulated results, a new electro-optic mode with optimization of both electrode structures and physical properties of the liquid crystal...

The development of low-frequency-driven liquid crystal displays (LCDs) has recently received intense attention to open up low-power consumption display devices, such as portable displays, advertising panels and price tags. In fringe-field switching (FFS) LCD mode, a unidirectional electric field gives rise to head-tail symmetry breaking in liquid crystals, so that the flexoelectric effect, a coupling between the elastic distortion and the electric polarization, becomes enormously significant. The effect is thus linked to an unusual optical effect, which badly damages the quality of images by image-flickering, and this image-flickering is mainly caused by transmittance difference between the applied signal frames. Here, we intensively investigate the mechanism of the transmittance deviation, and propose an essential and promising approach to solve the poor image-quality, that is, symmetrization of electric fields between the frames. The result of our work clearly demonstrates that the field-symmetry is crucial to reduce the image-flickering, and it can be obtained by optimization of the thickness of an insulation layer with respect to the ratio of the space between electrodes to the electrode width.

Recently, the driving scheme of a fringe-field switching (FFS) liquid crystal display varies for the best of required performance. Although low-frequency driving can effectively give rise to reduce power consumption in portable displays, proper controlling of liquid crystal director in direct current is challenging. Particularly, under different polarity of applied electric fields, the transmittance difference along the location of electrodes becomes significant, hence giving rise to an image flickering issue. Here, we investigate how physical properties of a bulk liquid crystalline medium are involved to locally modulate the transmitting light, numerically and experimentally.

Image-flickering due to flexoelectric effect in a low frequency driven fringe-field switching (FFS) LCD is troublesome. Maximization of transmittance in the FFS mode is achieved using LCs with negative dielectric anisotropy but still the flickering exists. The paper describes in detail on optimal solutions how it can be solved by controlling the ratio of electrode width to distance and thickness of passivation layer. The results greatly contribute to achieve high transmittance and image-flickering free FFS LCD. Author KeywordsFFS mode, image-flicker, flexoelectric effect, negative liquid crystal, fine-patterned electrode.