High-performance Liquid Crystal Research Articles

Refractive Fresnel liquid crystal lenses driven by two voltages.

We propose and demonstrate a high-performance refractive Fresnel liquid crystal (LC) lens with a simple electrode design. The interconnected circular electrodes enable the creation of a parabolic voltage distribution within each Fresnel zone using only two driving voltages. By controlling these voltages within the linear response region of LC material, the desired parabolic phase profile can be achieved. We provide a detailed discussion on the electrode structure design methodology and operating principles of the lens. In our experiments, we constructed a four-zone Fresnel LC lens with a total aperture of 8 mm. The results show that the optical power of the lens can be continuously adjusted from -1.30 D to +1.33 D. Throughout the process of electrically tuning the optical power, the phase distribution within each Fresnel zone maintains a parabolic profile. These results demonstrate the high-performance of the proposed Fresnel LC lens.

Layered B2O3/CsPbBr3 perovskite composite embedded using glass as microreactor with enhanced stability and high-efficiency light extraction

Lead halide perovskite quantum dots are considered to be one of the best candidates for the next generation of light conversion materials. However, their practical application is greatly hindered by its intrinsic poor stability and once exposed to air, heat moisture and illumination. Here, we report a novel reaction scheme that allows the simultaneous production of high-quality CsPbBr3 nanocrystals (NCs), self-healing process that optimized the crystallinity of CsPbBr3 NCs, and the formation of a protective coating layered structure of a densely packed two-dimensional B2O3 crystals with the assistance of water. Due to the inherent refractive index mismatch in the B2O3-CsPbBr3-B2O3 (B-C-B) laminated structure, excellent light extraction efficiency was achieved. The resulted layered B2O3/CsPbBr3 perovskite composite showed exceptionally high photoluminescence quantum yield (PLQY ∼90%) and excellent stability over 2 years under normal storage condition. A high-performance backlight liquid crystal display (LCD) was designed as B2O3/CsPbBr3 @ K2SiF6: Mn4+ (KSF: Mn4+) @ polydimethylsiloxanes (PDMS) monolithic film, which featured an optimal white emission (with correlated color temperature of 5327 K), that covered 130% of NTSC standard color gamut area of CIE1931, thereby demonstrating a great application potential in the optoelectronics industry.

Implication of Freeze-Thaw Erosion and Mechanism Analysis of High-Performance Aromatic Liquid Crystal Fibers.

According to the demand for high-performance fibers for high-latitude ocean exploration and development, this paper selects representative products of high-performance liquid crystal fibers: thermotropic liquid crystal polymer fibers (TLCP) and poly p-phenylene terephthalamide (PPTA) fibers. Through a series of freeze-thaw (F-T) experiments for simulating a real, cold marine environment, we then measure the retention of mechanical properties of these two kinds of fibers. Before that, due to the difference in their chemical structures, we tested their Yang-Laplace contact angle (YLCA) and water absorption; the results suggested that PPTA fibers would absorb more moisture. Surprisingly, then, compared with thermotropic liquid crystal polymer (TLCP) fibers, the retention of the mechanical properties of poly p-phenylene terephthalamide (PPTA) fibers decreased by around 25% after the F-T experiments. The Fourier-transformed infrared (FT-IR) analysis, the attenuated total reflection (ATR) accessory analysis and the degree of crystal orientation measured by two-dimensional wide-angle X-ray diffraction (2D-WAXD) confirm that no changes in the chemical and the orientation structure of the crystal region of the fibers occurred after they underwent the F-T cycles. However, as observed by scanning electron microscopy (SEM), there are microcracks of various extents on the surface of the PPTA fibers, but they do not appear on the surface of TLCP fibers. It is obvious that these microcracks will lead to the loss of mechanical properties; we infer that the moisture absorbed by the PPTA fibers freezes below the freezing point, and the volume expansion of the ice causes the collapse of the microfibrillar structure. The two sorts of fibers subjected to the F-T experiments are immersed in a sodium chloride solution, and the amount of water infiltrated into the PPTA microfibrillar structure is evaluated according to the content of sodium ions in the fiber surface and subsurface layers through X-ray spectroscopy (EDS) elemental analysis. From the above analysis, we found that TLCP fibers can more effectively meet the operating standards of the severe and cold marine environment.

High birefringence liquid crystals with a wide temperature range and low melting point for augmented reality displays

Precise molecular tailoring was applied to obtain high performance liquid crystal materials for the broad temperature adaptability of LCoS devices in AR displays.

Drug monitoring of the antibacterial drug Vancomycin in patients with purulent-inflammatory diseases of the maxillofacial region

To evaluate the change in the level of concentration of the antibacterial drug Vancomycin registered in the purulent focus area (facial vein) and in the peripheral blood flow (cubital vein) in patients with phlegmon of the maxillofacial region (MFR). The clinical material of the study was 12 patients with phlegmon of MFR who were being treated in the maxillofacial department of the N.I. Pirogov State Clinical Hospital No. 1 of the Moscow Medical Center. The drainage of phlegmons was performed on the day of admission of the patient 2-3 days after the onset of the disease. The phlegmons involved two or more spaces of the MFR. As an antimicrobial drug, 500 mg of Vancomycin in 400 ml of saline solution was used intravenously. Quantitative registration of Vancomycin was carried out 2 hours after intravenous infusion. Blood sampling was carried out from the cubital and facial veins in an amount of 7-8 ml intraoperatively at the opening of the phlegmon, under endotracheal anesthesia. The concentration of the antibiotic was determined by high-performance liquid crystal chromatography. The study found that the concentration of Vancomycin in the facial vein exceeds similar indicators obtained from the cubital vein. The difference in the percentage ratio averaged 19.2±7.3%. In 10 patients with phlegmons of various localization, it was found that the penetration of the antibacterial drug into the tissues of the inflammatory focus is higher compared to the periphery. However, in a number of patients, the concentration of the drug did not exceed the minimum suppressive concentration recommended for obtaining a therapeutic effect (for Vancomycin, it is at least 2 mcg / ml). To achieve the therapeutic effect of phlegmon treatment, it is necessary to select an individual dose of the drug for each patient.

Synthesis and properties of high performance biobased liquid crystal polyester based on furandicarboxylic acid and sebacic acid

In this study, a series of high-performance biobased liquid crystal copolyesters derived from 6-hydroxy-2-naphthoic acid (HNA), 4, 4ʹ-Dihydroxybiphenyl (BP), biobased 2,5-furandicarboxylic acid (FDCA) and sebacic acid (SeA) were successfully designed and prepared via “one-pot” melt polycondensation method. The addition of nonlinear and rigid FDCA units broke the regularity of the molecular chain but increased the chain rigidity, thus, endowing the unique thermal behavior, which the melting temperature decreased from 163.0 to 125.3 ℃, while the glass transition temperature decreased first and then increased slightly to 75.7 ℃ as increased the FDCA units to 7.5 mol%. Furthermore, DSC and XRD results showed that a small amount (1 mol%) of FDCA units did not impair crystallization ability of the copolyesters, whereas excess of FDCA hindered the molecular chain packing. The DMA results also demonstrated that the addition of FDCA restricts the chain motion and improves the rigidity of the copolyester as reflected by the higher storage modulus. The incorporation of nonlinear FDCA units lowered the initial degradation temperature slightly, but still exhibited enough thermal stability to be melt processed as compared with its relative low melting temperatures. The copolyesters exhibited a broad temperature range of nematic liquid crystal phase as well as shear thinning and viscous melt flow behavior, which were beneficial for its melt processing. The tensile strength and modulus of the injection molded splines were in range of 82.51–103.27 MPa and 2.05–2.72 GPa, respectively, which were much higher than the common biobased copolyesters such as PLA, PCL and other FDCA-containing polyesters. The increased modulus and decreased fracture strain of the copolyesters containing FDCA units further verified the high rigidity of the molecular chain. Moreover, the in-vitro cytotoxicity and water contact angle results proved that the copolyesters have good biocompatibility. The resulted copolyesters combined with excellent melt processing ability, mechanical property and good biocompatibility have great promising applications as biomedical and biodegradable materials.

Highly Miniaturized Continuously Tunable Phase Shifter Based on Liquid Crystal and Defected Ground Structures

This letter presents a highly miniaturized continuously tunable microstrip line phase shifter from 10 to 67 GHz. The design takes the advantage of the microstrip line topology by a ground plane with defected ground structures (DGSs). This leads to slow wave (SW) effect of the transmission line (TL), thus the TL can be physically compact, while maintaining its electric length. By applying tunable microwave liquid crystal (LC) with an anisotropic permittivity as dielectric, a delay line phase shifter is realized. The proposed microstrip LC phase shifter with DGS and a standard microstrip LC phase shifter as reference are both filled with 20-mm-thick high-performance LC GT3-23001. By comparison, the one with DGS exhibits a significant SW effect and an improved LC tuning efficiency which leads to a remarkable enhancement of figure of merit (FoM) and compactness than the reference. A second microstrip LC phase shifter utilizing DGS filled with 5-mm thick more advanced GT7-29001 LC shows outstanding FoM of 55°/dB, compactness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$201^{\circ }/{\lambda }_{0}$ </tex-math></inline-formula> , and response time of 210 ms.

High efficiency fluorescent perovskite quantum dots encapsulated in superhydrophobic silica aerogel for wide color gamut backlight displays

• A super-hydrophobic Silica Aerogels film for backlight display was prepared. • A wide gamut of 128% of color gamut of NTSC standard was achieved. • Excellent environmental stability was achieved through a composite strategy. Recently, all-inorganic cesium lead halide (CsPbX 3 ) perovskite quantum dots (PQDs) have been widely used in the photoelectric field. However, a major limitation of solution-processed PQDs for applications is inherent instability. Herein, we adopt strategy of passivation, CsPbX 3 (X = Cl, Br, I) PQDs are encapsulated into super-hydrophobic silica aerogels (SiO 2 AGs) to form a protective layer for resisting destruction by external forces. Importantly, the photoluminescence quantum yield (PLQY) of CsPbBr 3 @AGs composites achieves 71%, CsPbCl 2 Br 1 @AGs, CsPbBr 3 @AGs and CsPbBr 1 I 2 @AGs composites with narrow emissions can replace traditional phosphors as color converters. In addition, a high-performance liquid crystal display (LCD) with a wide color gamut (128% of National Television System Committee color space) is demonstrated using the prepared CsPbX 3 @AGs@PS composite film and blue light emitting diode (LED) chip as backlight. The combination of improved stability and wide color gamut of the perovskite material provides a viable approach for LCD backlight.

On the influence of thermal annealing on molecular relaxations and structure in thermotropic liquid crystalline polymer

The influence of thermal annealing on mechanical relaxations and microstructure of a high performance thermotropic copolyester was investigated using dynamic mechanical analysis. The copolyester consisted of random units of 73 mol % 1,4-hydroxybenzoic acid (B) and 27 mol % 2,6-hydroxynaphthoic acid (N), denoted B-N 73:27. As-extruded tapes exhibit a mechanical relaxation at ca. 105 °C denoted α and associated to cooperative molecular motions akin to the glass transition, and a mechanical relaxation ca. 60 °C denoted β and associated to motions of the N moiety. Thermal annealing at 240 °C (well above the glass transition) and without tension, enabled molecular rearrangements afforded by an initial reduction and then a steady increase of the activation energy of the α and β relaxations. Then, at the bulk level, the glass transition temperature Tg first decreased and then increased during annealing. The elastic tensile modulus E’ was an increasing function of annealing time and the temperature before mechanical failure increased from 200 to 240 °C. Regarding the microstructure, thermal annealing induced a phase transformation from pseudo-hexagonal to orthorhombic phase. Furthermore, the degree of crystallinity (and enthalpy of fusion) increased, the nanovoid width decreased and the correlation of B or N repeat unit matching was reduced as reflected by the broadening of the 002 meridional reflection. The initial reduction of activation energy appears a condition to enable molecular rearrangements leading to the eventual thermo-mechanical reinforcement. Thus, understanding of molecular rearrangements during thermal annealing enables tuning the physical properties by controlling the microstructure of high performance liquid crystal polymers.

Fast and Miniaturized Phase Shifter With Excellent Figure of Merit Based on Liquid Crystal and Nanowire-Filled Membrane Technologies

This paper presents a highly miniaturized tuneable microstrip line phase shifter for 5 GHz to 67 GHz. The design takes advantage of the microstrip topology by substituting the ground plane by a metallic-nanowire-filled porous alumina membrane (NaM). This leads to a slow-wave (SW) effect of the transmission line; thus, the transmission line can be physically compact while maintaining its electric length. By applying a liquid crystal (LC) with its anisotropic permittivity as substrate between the transmission line and the NaM, a tuneable microstrip line phase shifter is realized. Three demonstrators are identically fabricated filled with different types of high-performance microwave LCs from three generations (GT3-23001, GT5-26001 and GT7-29001). The measurement results show good matching in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$50\ \Omega$</tex-math></inline-formula> system with reflection less than −10 dB over a wide frequency range. These demonstrators are able to reach a maximum figure of merit (FoM) of 41 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> /dB, 48 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> /dB, and 70 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> /dB for different LCs (GT3-23001, GT5-26001 and GT7-29001, respectively). In addition, experiments show that all three LCs should be biased with square wave voltage at approximately 1 kHz to achieve maximum tuneability and response speed. The achieved response times with GT3-23001, GT5-26001 and GT7-29001 are 116 ms, 613 ms, and 125 ms, respectively, which are much faster than other reported LC phase shifter implementations. Large-signal analysis shows that these implementations have high linearity with third-order interception (IP3) points of approximately 60 dBm and a power handling capability of 25 dBm.

Impact of some mineral-based nanoparticles versus carbon nanoallotropes on properties of liquid crystal hydroxypropyl cellulose nanocomposite films

PurposeThis study aims to motivate the application of some low-cost minerals in synthesizing nanoparticles as effective additives on the performance of liquid crystal (LC) hydroxypropyl cellulose (HPC) nanocomposite film, in comparison with carbon nanoallotrope.Design/methodology/approachMetallic nanoparticles of vanadium oxide, montmorillonite (MMT) and bentonite were synthesized and characterized by different techniques (Transmission electron microscopy [TEM], X-ray diffraction [XRD] and Fourier transform infrared [FTIR]). While the XRD, FTIR, non-isothermal analysis thermogravimetric analysis, mechanical analysis, scanning electron microscope and polarizing microscope were techniques used to evaluate the key role of metallic nanoparticles on the performance of HPC-nanocomposite film.FindingsThe formation of nanoparticles was evidenced from TEM. The XRD and FTIR measurements of nanocomposite films revealed that incorporating the mineral nanoparticles led to enhance the HPCs crystallinity from 14% to 45%, without chemical change of HPC structure. It is interesting to note that these minerals provide higher improvement in crystallinity than carbon nanomaterials (28%). Moreover, the MMT provided film with superior thermal stability and mechanical properties than pure HPC and HPC containing carbon nanoparticles, where it increased the Ea from 583.6 kJ/mol to 669.3 kJ/mol, tensile strength from 2.25 MPa to 2.8 MPa, Young’s modulus from 119 MPa to 124 MPa. As well as it had a synergistic effect on the LC formation and the birefringence texture of the nanocomposites (chiral nematic).Research limitations/implicationsHydroxylpropyl cellulose-nanocomposite films were prepared by dissolving the HPC powder in water to prepare 50% concentration, (free or with incorporating 5% synthesized nanoparticles). To obtain films with uniform thickness, the prepared solutions were evenly spread on a glass plate via an applicator, by adjusting the thickness to 0.2 mm, then air dried.Practical implicationsThese minerals provide higher improvement in crystallinity than carbon nanomaterials (28%), moreover, the MMT and bentonite provided films with superior thermal stability than pure HPC and HPC containing carbon nanoparticles. The mineral nanoparticles (especially MMT nanoclays) had a synergistic effect on LC formation and the birefringence texture of the nanocomposites (chiral nematic).Social implicationsThis study presents the route to enhance the utilization of claystone available in El-Fayoum Province as the precursor for nanoparticles and production high performance LC nanocomposites.Originality/valueThis study presents the route for the valorization of low-cost mineral-based nanoparticles in enhancing the properties of HPC-film (crystallinity, thermal stability, mechanical strength), in comparison with carbon-based nanoparticles. Moreover, these nanoparticles provided more ordered mesophases and, consequently, good synergetic effect on LCs formation and the birefringence texture of the HPC-films.

66‐4: Reactive Monomers Optimized for Fast Response Liquid Crystals with High Reliability

The demand for fast response liquid crystals (LC) with high reliability for high performance liquid crystal displays (LCD) is increasingly urgent. In this work, the relationships between the conditions of the UV process and the reliability of fast response LC were investigated. By the application of novel reactive monomers (RM) with faster polymerization rate and longer reaction wavelength, a kind of fast response LC with high voltage holding ratio (VHR) and low ion concentration has been obtained. This work provides new insights for the improved reliability of fast response LC without electro‐optical performance loss.

Facile In Situ Fabrication of Cs4PbBr6/CsPbBr3 Nanocomposite Containing Polymer Films for Ultrawide Color Gamut Displays

AbstractA modified supersaturated recrystallization method for in situ fabrication of Cs4PbBr6/CsPbBr3 nanocomposite containing polymer films is reported. This facile and efficient strategy can be easily carried out at room temperature, and minimizes the contact time between CsPbBr3 nanocrystals and water and oxygen molecules during the formation of perovskite film, passivating the perovskite nanocrystals. Through the approach, the dual protection of Cs4PbBr6 and polymer matrix enhances the water stability and photostability of emitting CsPbBr3. Even after being immersed in water for 30 days, the Cs4PbBr6/CsPbBr3@PMMA film still retains a bright green fluorescence. Moreover, combining the as‐prepared green‐emitting Cs4PbBr6/CsPbBr3@PMMA and a red‐emitting CdSe/ZnS based quantum dots (QDs) polymer film with blue light emitting diode (LED) chips as the backlight, a high performance liquid crystal display (LCD) is demonstrated. The color gamut of the demonstrated display is 131% and 98% that of the NTSC 1953 and Rec.2020, respectively. The combination of better stability and improved color purity of the perovskite material intuitively provides a viable approach for LCD backlights.

Interference-free and single exposure to generate continuous cycloidal alignment for large-area liquid crystal devices.

An approach for generating cycloidal pattern of liquid crystal (LC) molecules based on interference-free and single exposure is illustrated. The spatial manipulation of polarization state is achieved using birefringent prism and wave plates. And then, the spatially variant polarization of exposure beam is transferred to LC molecules by azo-dye photo-sensitive layer. Consequently, the LC samples fabricated shows periodically cycloidal texture and diffraction efficiency more than 99%. The measured period Λ and diffraction angle are in good consistency with theoretical results. Thus, this exposure method provides an effective and robust way for fabricating large-area LC elements, therefore paving the way for widespread applications of high-performance diffractive LC devices.

33.3: High Performance Liquid Crystal Micro‐Lens Array Applied to Light Field Display

In this paper, high performance liquid crystal micro‐lens array is realized by adding the High‐Resistance layer and applying the specific driving waveform. Besides, this device is suitable to be utilized in the technique of light field display due to its polarization selectivity and tunability.

Temperature-Dependent Thermoelastic Anisotropy of the Phenyl Pyrimidine Liquid Crystal.

Controlling thermoelastic anisotropy of liquid crystals (LCs) is important for achieving reliable structural stability and efficient heat dissipation, especially for high-performance LC devices. A solid understanding of the thermoelastic anisotropy and its relation with the LC molecular structure is, however, still missing. Here, we studied the direction-dependent mechanical and thermal properties of 5-n-octyl-2-(4-n-octyloxy-phenyl)-pyrimidine (PYP8O8) in a wide temperature range, covering five phases (i.e., crystalline, smectic C, smectic A, nematic, and liquid), by Brillouin light spectroscopy and temperature wave analysis, respectively. We found that the mechanical anisotropy is much smaller than the thermal anisotropy at LC phases; both anisotropies show strong phase dependence, with the biggest change occurring at the crystalline to LC phase transition; and the anisotropy of the phonon mean-free path correlates with the structural anisotropy of the rigid core of the LC molecule. The analysis of the temperature-dependent thermoelastic anisotropy of LCs yields insights into structure-based phonon engineering.

The nano-scale pitch ferroelectric liquid crystal materials for modern display and photonic application employing highly effective chiral components: Trifluoromethylalkyl diesters of p-terphenyldicarboxylic acid

Design and studying of high-performance ferroelectric liquid crystal (FLC) materials targeted on high demand applications in display and photonic devices is described. Combination of high twisting ability with large spontaneous polarization (PS > 100 nC/cm2) resulted in promising FLC mixtures: almost defect-free alignment in electro-optical cells, the optical quality of the cells becomes comparable to that based on nematic liquid crystals, but switching is at least in order faster. The most important parameter is responsible for the remarkable performance of the materials is their ultra-short helix pitch as low as 65 nm. The key components of new mixtures provided the advanced properties are high-twisting diesters of terphenyldicarboxylic acid and chiral 1,1,1-trifluoroalkan-2-ols (FOTDA-n, n = 4–8). Analysis of origin of twisting power in SmC* phase, main difference with N* LC, relationship with chemical structure of chiral components are given. Thus, remarkable increase (up to 2.8-fold) of helical twisting power in the smectic C* (SmC*) phase upon lengthening of terminal alkyl chains from 4th to 8th homologues is observed for FOTDA-n. New chiral compounds, FOTDA-n, where n is 5 and higher, at concentrations as low as 25–33 mol.% in non-chiral BPP based SmC* host induce the helix pitch considerably below 100 nm.

Research progress of terahertz liquid crystal materials and devices

Liquid crystal (LC) is an excellent tunable functional material which can be controlled by the external stimulus such as electric field, magnetic field and temperature. Terahertz (THz) radiation in a frequency range of 0.1−10.0 THz, has enormous advantages such as a low photon energy, sensitivity to crystal lattice vibration, magnetic spins, hydrogen bonds, intermolecular interaction, and water, and high transparency to non-conducting materials. The THz technology, therefore, has great potential in a diverse range of applications from spectroscopy, security screening to biomedical technology and high-speed wireless communication. But the development of high-performance LC based tunable THz functional devices is still in its infancy stage. The dispersion of LC refractive index induces a comparatively low birefringence in the THz regime. The lack of transparent electrodes makes the electric tuning of LCs difficult to achieve. To achieve certain modulations requires a very thick THz layer, leading to several disadvantages such as high operating voltage, slow response and poor pre-alignment. In this paper, we first present the research progress of large birefringence LCs in THz range. A room-temperature nematic LC NJU-LDn-4 with an average birefringence greater than 0.3 in a frequency range from 0.5 to 2.5 THz is shown in detail. This kind of LC can remarkably reduce the required cell gap, thus reducing the operating voltage and response time. Then we summarize varieties of conventional THz devices based on LC. Many electrodes are used for THz range. Graphene which can be used as a perfect transparent electrode material in THz band is proposed. Not only tunable transmissive but also reflective THz waveplates are introduced. The thickness of the LC layer of the reflective one can be reduced to ~10% of that needed for the same phase shift at a given frequency in a transmissive waveplate. The same tunability as that in the transmissive type just needs half the thickness. We also introduce that LC can generate THz vortex beam based on a photopatterned large birefringence LC. In the area of LC based versatile THz metamaterial devices, the adjacent units of a metasurface layer, such as a fishnet or grating, are usually connected to each other which may cause low-quality (&lt;i&gt;Q&lt;/i&gt;) factor and polarization sensitivity, which is undesirable. We emphasize a graphene-assisted high-efficiency tunable THz metamaterial absorber. Few-layer porous graphene is integrated onto the surface of a metasurface layer to provide a uniform static electric field to efficiently control the LC, thereby enabling flexible metamaterial designs. The THz far-field and near-field with large modulation and fast response are realized. A magnetically and electrically polarization-tunable terahertz emitter that integrates a ferromagnetic heterostructure and the large-birefringence liquid crystals is also demonstrated to be able to generate broadband THz radiation and control the polarization of THz waves perfectly as well as LC based THz reflectarray. Last but not least, a temperature-supersensitive cholesteric LC used for THz detection is shown. It can not only measure the beam profiles but also detect the power values of THz waves generated from a nonlinear crystal pumped by a table-top laser. Quantitative visualization based on not only the thermochromic but also the thermal diffusion effect, can be used conveniently and effectively at room temperature. In this review, we summarize the latest progress of liquid crystal materials and components in THz and discuss the possible prospects of the combination of liquid crystal technology and THz technology. We envision that LCs will play a unique role in THz sources, THz functional devices and THz detectors.

Electro-optical properties of liquid crystal displays based on the transparent zinc oxide films treated by using a rubbing method

Liquid crystal (LC) alignment on inorganic films has been found to be affected by surface modification via ion-beam irradiation. In this study, ZnO films treated by rubbing with a velvet cloth were shown to be capable of aligning LC molecules in the direction of the rubbing. Uniform and homogeneous LC alignment was achieved on the rubbed ZnO films. By analysing the optical axes before and after the rubbing treatment, we confirmed an increase in the anisotropy of the ZnO films; this optical anisotropy contributed to the uniform orientation of LC molecules. Further, the electro-optical characteristics of the twisted nematic cells based on ZnO films were superior to those based on conventional polyimide layers. Our results indicate that the rubbing approach could be applied in the fabrication of high-performance LC displays.

Fabrication of new photoreactive vertical alignment thin layers for fast switching liquid crystal display

New photoreactive vertical alignment layers have been fabricated by spin coating the mixtures of polyimide (PI) and bi-functional monomers on the indium tin oxide substrate. Post ultraviolet (UV) surface treatment under electric field induced fast electro-optical switching of liquid crystal (LC) through formation of pre-tilted alignment layer. To investigate the effect of reactive monomers on the electro-optical properties of LC device, newly designed four types of monomers with different aromatic cores and photoreactive groups were applied to PI mixtures. Stable homeotropic alignment and fast response time in the LC device were achieved with a simple coating and subsequent UV process of monomer with both a phenyl core and methacrylic groups in the PI layer and it yields electro-optical performance superior to that achieved with the conventional PI alignment layer. This elegant approach provides a stable and fast switching LC alignment layer for high performance LC displays.