V‐shaped electro‐optical mode based on deformed‐helix ferroelectric liquid crystal with subwavelength pitch

Abstract— V‐shaped electro‐optical response is shown, both theoretically and experimentally, to be an inherent property of a deformed‐helix ferroelectric liquid‐crystal cell (DHFLC) under a special choice of the applied rectangular alternating‐electric‐field waveform, frequency, and cell geometry. In contrast to other known V‐shaped ferroelectric liquid‐crystal (FLC) modes, the discovered V‐shaped switching is observed in a broadband frequency range including 1 kHz, and not at a certain characteristic frequency. This type of V‐shaped switching allows for a drastic increase in the operating frequency of field‐sequential‐color (FSC) LCD cells in comparison with fast nematic liquid‐crystal (NLC) modes.     

Multistable electro‐optical modes in ferroelectric liquid crystals

Abstract— Multistable electro‐optical modes exist under certain conditions in ferroelectric liquid‐crystal (FLC) cells, which means that any light‐transmission level can be memorized after the driving voltage is switched off. The multistability is responsible for three new electro‐optical modes with different shapes of the gray‐scale curve that can be either S‐shaped (double or single dependent upon the applied‐voltage pulse sequence and boundary conditions) or V‐shaped dependent upon boundary conditions and FLC cell parameters. The origin of these modes will be described.     

Switchable helical holographic structures

Abstract— A 3‐D array of helical structures fabricated using holographic polymer‐dispersed liquid crystals (H‐PDLC) is presented. Multiple coherent beams are interfered to create a constructive helical pattern which is permanently captured using the standard H‐PDLC method. Films with such array of helical structures have both diffractive and circular polarization sensitive reflective properties. Iso‐intensity patterns, design parameters, fabrication process, optical/electro‐optical performance of these periodic helical structures are discussed along with their potential application for advanced electro‐optical devices.     

Reduced dc offset and faster dynamic response in a carbon‐nanotube‐impregnated liquid‐crystal display

Abstract— Liquid crystals have been extensively employed in photonic devices, especially in current flat‐panel displays. Demands on high‐quality electro‐optical performance of liquid‐crystal displays have continued to impel delicate molecular designs, chemical syntheses, as well as advanced cell‐manufacturing processes, leading to a reduced dc offset and faster intrinsic response in the devices. Here, a novel approach toward the reduction of the residual dc and response time is reported based on carbon‐nanotube doping. It is demonstrated that a minute amount of carbon nanotubes as a dopant can suppress the unwanted ion effect, invariably lower the rotational viscosity, and modify other physical properties of the liquid crystals, giving the approach an opportunity in display applications.     

New non‐synthetic method to modify properties of liquid crystals using micro‐ and nano‐particles

Abstract— The modification of the properties of existing LCs by doping them with ferroelectric micro‐ and nano‐particles will be reported. This approach, in contrast to the conventional time‐consuming and expensive chemical synthetic methods, enriches and enhances the electro‐optical performance of many liquid‐crystal materials. The effect of the ferroelectric particles on the nematic, smectic, and cholesteric phases will be discussed. The performance of these new composite systems in various devices, including displays, light modulators, and beam‐steering devices, will be reported.     

Influence of alkyldiacrylate side‐chains on electro‐optical properties in liquid crystal/composite films

In order to realize a paper‐like display using polymer‐network liquid‐crystal (PNLC) films, an increase in backscattering intensity is required. The morphology of the films, and the molecular interactions between the liquid crystals and polymers forming the polymer network, both play an important role in determining film electro‐optical properties such as the driving voltage and the reflectance. We have analyzed several factors related to the morphology of the films. Aiming at a reduction in the driving voltage, the effects of alkyl side‐chains in diacrylates have been investigated. Based on the results, we successfully produced a prototype paper‐like display.     

Tailored liquid‐crystal switching on ferroelectric polymer films

Abstract— The development of voltage‐controlled visible‐wavelength progression in displays and optical data storage devices using ferroelectric polymers and liquid crystals is described. Ferroelectric polymers are materials that have a ready distribution of dipoles which can be oriented by manipulating material composition and external fields. Utilizing the charge polarization distribution, their performance as an alignment layer for inducing liquid‐crystal alignment is presented. The switching response of the devices was tailored by changing the material composition through copolymers and nanoclay doping.     

Optimization of photo‐aligned ferroelectric liquid‐crystal display under passively addressed driving

Abstract— A ferroelectric liquid‐crystal (FLC) passively addressed 64 × 64 display based on the photo‐alignment technique has been developed. The display matrix has dimensions of 33 × 33 mm², and the FLC layer thickness is about 5 μm. Asymmetric boundary conditions, when only one of ITO surfaces of the display matrix is covered with the photo‐aligning layer while another one is not, have been used for providing both high contrast ratio and steady multiplex operation. The electro‐optical performance of the 5‐μm FLC display is presented, including bistable switching in static operation, optimization in multiplexing operation, and gray‐scale generation.     

Electro‐optic effects of the optically isotropic state induced by the incorporative effects of a polymer network and the chirality of liquid crystal

Abstract— The electro‐optical properties of optically isotropic liquid‐crystalline composites prepared by in‐situ photo‐polymerization of cross‐linking monomers in the isotropic phase of chiral liquid crystals were investigated. The magnitude of the electric birefringence of the composites decreased as the chirality of the liquid crystal increased. The clear Kerr effect was observed for the composites with high chirality. A large Kerr constant, being relatively insensitive to temperature, was obtained for the composites even in a temperature range below the isotropic‐chiral‐nematic phase‐transition temperature. The response time of the Kerr effect at room temperature was on the order of tens to hundreds of microseconds.     

Electrically suppressed helix ferroelectric liquid crystals for modern displays

In this article, we disclose electrically suppressed helix ferroelectric liquid crystal (ESHFLC) that is characterized by high optical quality and fast response time at the cost of extremely small driving voltage. These unique features of the ESHFLCs are highly sensitive to the anchoring energy that should be smaller and comparable to the elastic energy of the ferroelectric liquid crystal helix. The photo alignment, which offers good control on the anchoring energy by means of the irradiation energy, is critically important to lock the optimum parameters of the ESHFLC display cell. An example of field sequential color display with the frame frequency of 240 Hz at the driving voltage of 2 V has been demonstrated.     

Plasma‐beam alignment of passive liquid crystals (Invited Paper)

Abstract— A plasma‐beam process, developed for the alignment of liquid crystals (LC) in electro‐optic applications, has been successfully applied to align “non‐standard” LC, such as crystalline materials with LC phases at elevated temperatures and reactive mesogenes. In addition to the high alignment quality of the materials, there is no need for an intermediate layer between the substrate and the LC layer. Furthermore, the construction of our source simplifies the alignment procedure of large‐area rigid substrates and the roll‐to‐roll processing of flexible films. This method opens new horizons for optical retarders and polarizers, as well as anisotropic semiconducting films for organic electronics.     

Defect‐free deformed‐helix ferroelectric liquid‐crystal mode in a vertically aligned configuration (Invited Paper)

Abstract— A novel deformed‐helix ferroelectric liquid‐crystal (DHFLC) mode in a vertically aligned (VA) configuration is described. In this configuration, several unique features of display performance such as uniform alignment, fast response, and analog gray‐scale capability are obtained. Particularly, this VA‐DHFLC mode allows for the defect‐free uniform alignment of both the FLC molecules and the smectic layers over a large area without employing additional processes such as rubbing or electric‐field treatment that are generally required for planar FLC modes. Based on the VA‐DHFLC mode, a transflective display having a single‐gap geometry with in‐plane electrodes on two substrates in the transmissive regions and on one substrate in the reflective regions is described.     

Fast phase modulation using dual‐frequency nematic liquid crystals

Abstract— Experimental study and numerical simulations of optical phase modulators based on nematic liquid crystals characterized by frequency sign inversion of the dielectric anisotropy has been performed. The received results point out an extreme role of back‐flow effects and electro‐hydrodynamic instability, which make restrictions for creating high‐speed phase modulators with large switchable values of phase retardation. It is shown by numerical simulations that the hydrodynamic destabilization can be suppressed by decreasing the ratio of Leslie coefficients |α²/α^4,5|.     

A novel approach to LCD optimization

Abstract— A novel approach to optimization liquid‐crystal displays (LCDs) is presented. The optimization module allows for a prediction with a high accuracy for the best results, which can be obtained for one or the other configuration of the polarizers and phase retarders in various electro‐optical modes, if the LC parameters and the operating voltages are fixed. The module is a part of our program, MOUSE‐LCD, which is efficient software for LCD optimization and modeling.     

Simulation and fabrication of a fast fringe‐field switching liquid crystal with enhanced surface anchoring enabled by controlled polymer topology

We demonstrate a fringe‐field switching nematic liquid crystal with electro‐optical behavior modulated by both bulk and surface polymer stabilization. The polymer is formed by ultraviolet irradiation‐induced phase separation of various amounts of a reactive monomer in the planar‐aligned nematic liquid crystal. Simulation is carried out to verify the effect of anchoring energy. Experimental evidence validates the effect of monomer concentration on transmittance–voltage and response times curves of fringe‐field switching cells. The polymer‐stabilized alignment with a higher polymer concentration escalates the interaction between the liquid crystal and the polymer structure and increases the surface anchoring energy. The polymer stabilization also improves the dynamic response times of liquid crystal. The enabling polymer‐stabilized alignment technique has excellent electro‐optical properties such as a very good dark state, high optical contrast, and fast rise and decay times that may lead to development of a wide range of applications.     

Processes,characterizations, and system applications of color‐filter liquid‐crystal‐on‐silicon microdisplays

Abstract— A color‐filter liquid‐crystal‐on‐silicon (CF‐LCOS) microdisplay that integrates color filters on silicon for color will be presented. The color‐filter process on silicon was optimized to achieve fine resolution and precise alignment of the color filters on the pixel array, good adhesion to the silicon suface, and a flat surface for the liquid‐crystal cell assembly. Important optical and electrical parameters of the color filters were extracted to establish an electro‐optical model of the CF‐LCOS microdisplays for device simulation. Thermal, chemical, and light‐stability characterizations were performed to ensure the stabilty of the color filters and CF‐LCOS microdisplays. With color CF‐LCOS microdisplays already available, the projection or viewing optics is greatly simplified. This CF‐LCOS microdisplay is ideal for near‐to‐eye displays because of its low‐power consumption and compactness. The CF‐LCOS microdisplay could also withstand medium light illumination for medium‐sized projectors. A single‐panel projector based on one CF‐LCOS microdisplay of 1280 × 768 × RGB resolution was demonstrated.     

Dynamic parameters of electrically controlled light scattering in helix FLC cells

Abstract— The light‐scattering structures in monomeric FLCs have been considered and a mechanism for the scattering on transient domains in the helix layers has been proposed. An optical response with a bistable characteristic of light scattering and transmission was realized at a defined electrical pulse regime and boundary conditions in electro‐optical FLC cells. The total time of the scattering switching on and switching off is less than 400 μsec at ±36 V. They are quite fast, and FLC cells are quite transparent to be used in a stack of 30–100 light‐scattering shutters for a volumetric screen of a 3‐D display.     

Hollow fibers containing various display elements: A novel structure for electronic paper

Abstract— A novel structure for electronic‐paper displays using hollow fibers has been developed, where the hollow fiber is comprised of an outer transparent polymer tube and inner display elements (rotating balls, electrophoretic dispersion fluid, or cholesteric liquid crystals). The structure composed of thin polymer fibers is capable of realizing paper‐like visibility and flexibility, which are vital properties required for electronic‐paper displays. Hollow fibers containing display elements were produced through an industrial manufacturing process using a conventional melt spinning method for the first time and showed electro‐optical switching when the voltage was applied. The hollow fibers were then woven into fabric sheets. The structure and the production process for electronic paper in this study will be a candidate for a simple method to produce large‐area electronic‐paper displays.     

Ferroelectric properties of LC systems including chiral dopants with different molecular structure

Abstract— New ferroelectric liquid crystals (FLCs) on the basis of the eutectic mixture of phenylbenzoate derivatives including chiral components (CCs) with a different number and position of carbonyl groups in their molecular core have been investigated. The ferroelectric characteristics such as the spontaneous polarization, smectic tilt angle, rotational viscosity, and repolarization time as well as their concentration dependences are analyzed. On the basis of the previous and obtained results, the influence of peculiarities of the molecular structure of CCs on mentioned properties of FLCs are generalized.     

Feasibility study of novel fast‐switching liquid crystal displays using electric birefringence effect

Both theoretical and experimental studies were made on electric birefringence effect of nematic liquid crystals in isotropic phase with respect to its applicability to novel LCDs. It was confirmed that response times are <1 ms, and a critical point exists where electro‐optic hysteresis vanishes. Substrate surface treatments were also found to improve the electro‐optic characteristics. The results are promising for both projection and direct view display applications featuring fast switching and high image quality.