This article proposes a methodology to prepare polymer dispersed liquid crystal (PDLC) films working in the reverse-mode operation, where the ion-doped nematic liquid crystals (NLCs) with negative dielectric anisotropy (Δε) were locked by polymer walls. On-state and off-state of films were controlled by an electric field. In the absence of an electric field, it appears to be transparent. In the field, the homogeneous alignment NLCs form dynamic scattering, giving rise to opaque. The effect of the cylindrical holes with different diameters of photo masks and liquid crystal Δε on the electro-optical properties and transmittance wavelength range of 400–3000 nm light of samples were investigated. It was found that it exhibited very good electro-optical characteristics, high contrast ratio and excellent infrared energy-efficient of films used as switchable windows. 相似文献
ABSTRACTThe rapid development of consumer electronics and portable devices imposes a great demand for energy efficient information display systems. Among the information display devices, liquid crystal display (LCD) devices stands in the front. The fabrication of energy-efficient LCD systems demands new material and techniques. In this work, the conventional polyimide alignment layer of twisted nematic liquid crystal device (TNLCD) was replaced with ferroelectric polymer nanoparticle doped alignment layer. Morphology of the alignment layer was analysed using field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The ferroelectric nature of the polymer alignment layer was studied using dynamic contact electrostatic force microscopy (DC-EFM). TNLCD cells are fabricated with this modified alignment layer and the switching characteristics are compared with the conventional TNLCD devices. The TNLCD with modified alignment layer has shown a reduction of 50% in threshold (Vthr) and 47% reduction in saturation voltage (Vsat). 相似文献
ABSTRACTWith the increasing development of multifunction liquid crystal displays (LCDs), multifunction optical diffusers have attracted more attention. In this work, switchable optical diffusers based on the transient polymer balls-networks in polymer/nematic liquid crystal composite films have been prepared and investigated, and the effects of thiol content, curing time, LC content and photo-initiator content on the polymer microstructures and optical properties of optical diffusers are systematically studied. An optical diffuser with the transient polymer balls-networks microstructure has achieved the high transmission (96.42%), high haze (90.49%), excellent optical diffusing ability and wide viewing angle of 150° (from ?75° to 75°) on its off state. By the application of electric field of 40.0 voltage, the viewing angle of the optical diffuser turns to be narrower (from ?60° to 60°), which gives great applications in tunable viewing angle devices and other electric optical devices. 相似文献
A method for a continuous control of the pretilt angle of the easy axis in the range 0–90° degrees and of the anchoring strength by using nanostructured polymers as alignment layers is described. The nanostructured polymers are blends of two different side-chain polymers each of them promoting planar and homeotropic alignment, respectively. A model to interpret the alignment of a nematic liquid crystal induced by such polymer layers is proposed. We show that in this case the anisotropic part of the surface tension can be approximated by a simple extension of the Rapini–Papoular expression. The predicted trend of the pretilt of the easy axis versus the concentration of the side-chain polymer promoting the planar alignment, for instance, is in good agreement with the experimental data. We also show that the effective anchoring strength of the system depends on the concentration of the side-chain polymer promoting planar alignment, and exhibits a minimum for a well-defined value of this quantity. The results obtained in this work seems to be of importance for liquid crystal displays technology since the control of the pretilt and the anchoring strength strongly affect the performance of liquid crystal displays. 相似文献
Summary: The 3,4‐ethylenedioxythiophene (EDOT) monomer in a chiral nematic liquid‐crystal electrolyte was polymerized by application of a voltage to yield a thin film. Circular dichroism measurements indicated a Cotton effect for the film. Optical texture suggests that the polymer shows a finger‐print texture and a spiral texture similar to that of the chiral nematic phase. This simple method provides a new technique for preparing chiral conducting films in a thermotropic chiral liquid‐crystal field.
Optical micrograph of (R)‐PEDOT* (no polarizer). 相似文献
Ultrafast switchable wide angle negative refraction in a novel dual-frequency liquid crystal mixture is demonstrated experimentally. Laterally fluorinated isothiocyanato phenyl-tolane liquid crystal compound is doped into Merck MLC-2048 to acquire the high birefringence dual-frequency liquid crystal. The maximum negative refraction angle achieved is about 12° and the switching time is only 25 ms for a 40-μm cell which is two orders faster than switchable negative refraction achieved before in nematic liquid crystals. Such properties provide a feasible approach to design negative refraction devices based on liquid crystals. 相似文献
Stimuli‐directed alignment control of liquid crystals (LCs) with desired molecular orientation is currently in the limelight for the development of smart functional materials and devices. Here, photoresponsive azo thiol (AzoSH) was grafted onto gold nanoparticles (GNPs). The resulting hybrid GNPs were able to homogeneously mix with a commercially available nematic LC host, as evidenced by Cryo‐TEM. Interestingly, the LC nanocomposites were found to undergo reversible alignment transition upon light irradiation as a consequence of the trans–cis photoisomerization of the azo groups on the GNP surface. LC molecules in either planar or bare glass cells were able to change their alignment to vertical upon UV irradiation, while the vertically aligned LC molecules returned to the planar or random orientation under visible irradiation. Neither the azo thiol molecules nor the unfunctionalized GNPs alone promoted the alignment of the LC molecules in the system upon light irradiation. The photoinduced vertical alignment without applied electric or magnetic field was very stable over time and with respect to temperature. Furthermore, an optically switchable device based on the photostimulated reversible alignment control of LCs was demonstrated. 相似文献
Dielectric studies of the first order phase transition of a ferroelectric liquid crystal material having the phase sequence chiral nematic to smectic C* have been performed using thin (2.5 mum) cells in the frequency range 0.01 Hz to 12 MHz. For planar alignment, one of the cell electrodes was covered with a polymer and rubbed. Optically well defined alignment was obtained by applying an a.c. field below the N*-SmC* transition. Charge accumulation was enhanced by depositing a thick polymer aligning layer for the alignment of the liquid crystal molecules. A sub-hertz frequency dielectric relaxation process is detected in smectic C*, in the chiral nematic and a few degrees into the isotropic phase, due to the charge accumulation between the polymer layer and the ferroelectric liquid crystal material. The effect of temperature and bias field dependences on the sub-hertz dielectric relaxation process are reported and discussed. 相似文献