Ferroelectric Liquid Crystal Material Research Articles

Ferroelectric liquid crystal materials synthesized from 2(S)-[2(S)-methylbutyloxy]propanol

Abstract A new chiral alcohol, 2(S)-[2(S)-methylbutyloxy]propanol (3), containing two chiral centres has been synthesized from ethyl lactate and (S)-1-iodo-2-methylbutane. It was used as a chiral building block for the preparation of ferroelectric liquid crystal materials. Several of the new materials exhibit an enantiotropic S*c phase with a wide temperature range. The results indicate that the molecular structure of 3 is useful for synthesizing ferroelectric liquid crystal materials.

Optical and dielectric properties of antiferroelectric liquid crystals and their surface effects

Abstract A detailed study of the dielectric and optical properties of the ferroelectric liquid crystal material (R)-4′-(3-methoxycarbonyl-2-propoxycarbonyl)phenyl 4-(4-(n-octyloxy)phenyl)benzoate (3MC2PCPOPB) has been carried out. It has been found that an anomalous temperature dependence of the dielectric constant in 3MC2PCPOPB is due to the antiferroelectric and ferrielectric properties. A T(temperature)-E(electric field) phase diagram has been obtained on the basis of the apparent tilt angle measurements. In a thin cell (< 3 μm), both ferroelectric and antiferroelectric domains are simultaneously observed over a wide temperature range, and the complete antiferroelectric phase does not appear even at low temperature. A characteristic texture in which boundary focal conics are aligned parallel to a smectic layer has been observed. The movement of the zig-zag defect line caused by the application of the voltage is also observed.

Invited Lecture. Ferroelectric liquid crystalline polymers and related model compounds with a low–moderate degree of polymerization

Abstract Ferroelectric liquid crystalline polymers (FLCPs) with a low-moderate degree of polymerization were synthesized. These had a comb structure; the main chain was polyacrylate and the side chain consisted of a flexible spacer, a core and an optically active chiral end group. They exhibited electro-optic switching times ranging from a few milliseconds to a few seconds in the S*c phase. As the molecular weight M n increased, the range of the S*c shifted to higher temperatures. At a given temperature, the switching time increased with M n . Spontaneous polarizations P s , apparent cone angles 2θ, electro-optic switching times τ and rotational viscosities η of some polyoxyethylene FLCPs and corresponding low molecular weight ferroelectric liquid crystal materials (FLCs) were also measured. This is the first report of polyoxyethylene FLCPs. There was no significant difference in P s and 2θ, which shows that the arrangement of the side chains in the FLCP is similar to that of the molecules in ordinary FLC. On the contrary, τ and η for the FLCPs were 102–103 times as large as those for FLCs. The rotational viscosity of the FLCP was mainly dependent on the side chain structure rather than on the spacer. Therefore collisions between adjacent side chains cause large η values in FLCPs rather than hindrance to side chain gyration due to the spacer group. By combining FLCPs with ITO-coated plastic substrates, a large area matrix driven display has been made. Although an improvement in switching time is still needed, a flexible and lightweight display like a sheet of paper will be available in the near future.

Electrically tunable ferroelectric liquid-crystal Fabry–Perot filter

An electrically operated device that can switch between two wavelengths is described. The device operates by using an electrically switchable optically anisotropic material such as a liquid crystal in a Fabry-Perot cavity. The anisotropy produces two distinct cavity resonances that determine the two wavelengths. The electric field interchanges the slow and the fast optical axes of the anisotropic ferroelectric liquid crystal and thus allows switching from one wavelength to the other. It is shown that this device structure can be used as a polarization-sensitive switch with an extinction ratio of better than 100:1. This is true only for a class of ferroelectric liquid-crystal material that has a title angle of 45 degrees .

Bipolar optical neural networks using ferroelectric liquid crystal devices

Ferroelectric Liquid Crystal (FLC) electrooptic devices present some characteristics that make them attractive for the optical implementation of neural computers: high response speed and bistability, or intrinsic memory capability. Herein we will demonstrate how the electrooptic bistability of FLC materials can be used to implement bipolar optical neural networks, based on simple FLC cells that act as the neurons and as the interconnections among them.

Dielectric studies of ferroelectric liquid crystals

The dielectric properties of some ferroelectric alpha-chloroester thiobenzoate liquid crystal materials have been studied using a Du Pont 2970 dielectric analyzer (DETA) in the 0.01 Hz-100 kHz range. These materials exhibit smectic A and chiral smectic C mesophases, as well as additional mesophases in some cases. Transitions involving the chiral smectic C phase are of most interest because this phase has ferroelectric properties. The effect on these transitions of fluorine addition to the alkoxy tail was investigated. The Goldstone mode and soft mode are seen in the frequency dispersion curves of the dielectric loss factor. Very low heating rates of 0.01°C min −1 and small step-wise increments are possible, providing measurements at small temperature increments which permit close observation of the transition regions. DSC measurements and optical microscopy observations were also performed and the three techniques were found to be complementary.

The measurement of second-harmonic generation in novel ferroelectric liquid crystal materials

We present the analysis of experimental results on second-harmonic generation in a novel ferroelectric liquid crystal (FLC) material, o- nitroalkoxyphenyl biphenylcarboxylate 1, synthesized specifically for large nonlinear coefficients. All nonzero dij coefficients have been measured, with the largest being d22 = 0.6 ± 0.3 pm/V. Relative values of refractive indices are also given suggesting uniaxial optical properties with large birefringence (nz − nx≊ 0.20 at λ=1.064 μm). This material demonstrates the flexibility of FLC molecular synthesis to form thermodynamically stable macroscopically aligned materials for second-order nonlinear optics applications.

A new FLC-EO cell showing quasi-tristate characteristics

Abstract A novel ferroelectric liquid crystal (FLC) EO (electro-Optic) cell showing a quasi-tristate has been demonstrated by using an FLC material ZLI-4139 (Merck) together with orientation films of polyimide RN-626 (Nissan Chem. Ind) which are rubbed in antiparallel way and are capable of generating a high pretilt angle. The EO cell showing the quasi-tristates was characterized in term of the dynamic behavior of the dielectric constant, switching current, and D-E hysteresis.

A high-resolution and high-speed ferroelectric liquid-crystal shutter array print head

A 1-in-wide, 577-dot/in, and 4:1 multiplex ferroelectric-liquid-crystal (FLC) shutter array has been fabricated and tested for optical performance. The array has a cell gap of 2.8 mu m and is surface stabilized with an FLC material of high spontaneous polarization (140 nC/cm/sup 2/) and fast switching time (16 mu s) at room temperature. It is capable of operating at a speed of 6.5 in/s (24 p.p.m. printing speed) with optical contrast ratios of better than 4. Using tungsten-halogen illumination, a prototype print head has been made, and print samples have been obtained on an electrophotographic printer engine.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ferroelectric liquid crystal materials 4-[2-(4-alkylbicyclo[2,2,2]octyl)ethyl]phenyl 4-alkoxybenzoates, their mesomorphic properties and behaviour in mixtures

Abstract Some new compounds incorporating the 1,4-disubstituted bicyclo[2,2,2]octane ring have been synthesized, and their usefulness for preparing mixtures with a broad range of the smectic C phase and the SC ⟹ Ch or SC ⟹ Ch SC ⟹ SA ⟹ Ch phase sequences are tested.

Dielectric studies of the soft mode and Goldstone mode in ferroelectric liquid crystals

Abstract Different contributions to the dielectric permittivity in ferroelectric liquid crystals are discussed, with emphasis on the soft mode and the Goldstone mode and their location in the dielectric spectrum. Experimentally, the complex dielectric permittivity has been studied as a function of temperature and frequency in the range 5 Hz - 13 MHz for three different ferroelectric liquid crystal materials. The main problems encountered in dielectric measurements at low and high frequency are discussed in some detail. The soft mode dielectric behaviour has been studied as a function of temperature, frequency and bias electric field. The applicability of the Curie-Weiss law for the soft mode dielectric contribution in the A* phase was analyzed. In the C* phase the temperature dependence of the dielectric contribution of the Goldstone mode has been measured. By applying a bias electric field, we have been able to study the soft mode dielectric behaviour also deep into the C* phase. In the A* and C* phases the relaxation frequency and the inverse of the dielectric strength of the soft mode vary linearly with |T-TC|, which can be used to determine the A*-C* transition temperature to a good accuracy. The ratio of the slopes of the soft mode relaxation frequency vs temperature line and the inverse of dielectric strength vs temperature line in the C* and A* phases has been calculated for the three compounds and compared with solid ferroelectric systems. The soft mode rotational viscosity in the A* phase has been calculated for one of the compounds.

ChemInform Abstract: New Ferroelectric Liquid Crystal Materials: (+)-4-(5-Alkyl-1,3-dioxan-2-yl)phenyl 4-(2-Methylbutoxy)benzoates.

ChemInformVolume 21, Issue 20 Article ChemInform Abstract: New Ferroelectric Liquid Crystal Materials: (+)-4-(5-Alkyl-1,3-dioxan-2-yl)phenyl 4-(2-Methylbutoxy)benzoates. Y. HARAMOTO, Y. HARAMOTO Dep. Appl. Chem., Yamanashi Univ., Kofu 400Search for more papers by this authorH. KAMOGAWA, H. KAMOGAWA Dep. Appl. Chem., Yamanashi Univ., Kofu 400Search for more papers by this author Y. HARAMOTO, Y. HARAMOTO Dep. Appl. Chem., Yamanashi Univ., Kofu 400Search for more papers by this authorH. KAMOGAWA, H. KAMOGAWA Dep. Appl. Chem., Yamanashi Univ., Kofu 400Search for more papers by this author First published: May 15, 1990 https://doi.org/10.1002/chin.199020072Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume21, Issue20May 15, 1990 RelatedInformation

Ferroelectric Liquid Crystalline Compounds Having a Chiral Center Directly Connected to the Core Aromatic Ring. Synthesis of Chiral 4-(1-Propoxyethyl)benzenol and-benzoic Acid, 4-(1-Carboxyethyl)benzenol and the Esters Derived Therefrom

Abstract The title compounds were prepared through asymmetric reductions and derivatized into the ester compounds which were shown to be potent chiral dopants for ferroelectric liquid crystal materials.

Second-harmonic generation in ferroelectric liquid crystals

We present phase-matched, second-harmonic generation in the ferroelectric liquid-crystal material SCE9 (manufactured by BDH Ltd.). From the analysis of these results, the absolute values of all nonzero components of the d tensor have been obtained. A direct comparison between this material and the most efficient ferroelectric liquidcrystal material reported so far (ZLI3654) is made, which shows that SCE9 is four times more efficient at frequency doubling. At the phase-matching angle (theta = 19.1 degrees ) a d(eff) of 0.010(1) x 10(-12) m/V is measured. The results are consistent with near uniaxiality, the extent of which has been determined from experimental data (n(y) - n(x) = 0.0003, n(2) - n(x) = 0.17).

Dielectric anisotropy and dielectric torque in ferroelectric liquid crystals and their importance for electro-optic device performance

Measurements of the relevant anisotropic part of the dielectric constant for ferroelectric liquid crystals allows a calculation of the dielectric torque acting upon the director during addressing conditions in a matrix-multiplexed device. The frequency dependence of the dielectric anisotropy is presented for different commercially available ferroelectric liquid-crystal materials in the range 103–106 Hz. The field dependence of the switching time has been measured for one of the materials in order to determine the field at the minimum value. The ratio between this field and the field at which switching ceases has been determined and found to be in good agreement with the theoretically calculated value. The results enable us to consider the torque balance as a function of field and frequency, and thereby identify appropriate driving conditions.

Characterization of reorientation of a thin layer of ferroelectric liquid-crystal material under an applied field by excitation of optical modes

The director configuration in a thin layer of ferroelectric liquid crystal (FLC) under an applied static field is investigated by exciting optic modes in a FLC cell. The reflectivity data obtained may only be fitted to theory by maintaining in the voltage-distorted optical tensor profile a point in the middle of the cell having the same structure as at 0 V. This unambiguously confirms the chevron structure observed in x-ray diffraction and shows that the layering remains largely undistorted to fields of order 3×106 V m−1.

Multiplexed ferroelectric liquid crystal display

Abstract The studies on the fundamental requirements for realization of a multiplexed ferroelectric liquid crystal (FLC) display have been presented as follows: (1) The new classes of 2,5-diphenylpyrimidine FLCs are useful as a blending component for broadening the Sc temperature range and improving the switching response time. (2) A FLC material with the Iso-N-SA-Sc phase transition sequence as well as the long Sc and N helical pitches is required to achieve the homogeneous alignment in a Sc phase. (3) Among the FLC cells with various alignment layers, the PI/PI coated cell exhibits the symmetric and steep bistability threshold behavior. (4) The parameters to evaluate the multiplexing capability of a FLC cell are introduced and applied to select a suitable combination of alignment layers for highly multiplexing. (5) The parameters are also used to evaluate a favorable drive method among the drive schemes proposed so far for multiplexing a FLC cell. On the basis of the above studies, a multicolor ferroele...

Technic of Filling Occlusal Cavities in Bicuspids and Molars with Gold Foil

We report the dispersion of Cd1−xZnxS/ZnS core/shell nanocrystals (NCs) in ferroelectric liquid crystal (FLC) into different concentrations. Absorbance of white light, photoluminescence (PL), contrast, polarizing optical microscopy and Fourier transformed infrared spectroscopy (FTIR) have been performed to disclose the nature of FLC/NCs composite. The presence of NCs, in different concentration, quenches the PL of FLC material. The mechanism of quenching is explained by the modified Stern–Volmer quenching equation. The maximum contrast for FLC/NCs was found at 0.25 wt% of dopant concentration which is the optimized concentration of NCs in FLC from application point of view. Contrast was further supported by polarizing optical micrographs (POMs). The change in POM also indicates the change in molecular alignment of FLC owing to concentration of NCs which also affect the optical properties of composites. FTIR spectra reveal that the NCs strongly interact with FLC molecules and changes their molecular dynamics associated with the central core and aliphatic chain. The present FLC/NCs composite has potential application in ultraviolet to visible light conversion, ultraviolet light storage applications and high contrast PL displays.