Influence of curing temperature and high birefringence on the properties of polymerstabilized liquid crystals

We report the curing temperature effect on the performance of polymer-stabilized liquid crystals at lambda = 1550 nm. The curing temperature in the polymerization process is found to make a significant impact on the light scattering efficiency, hysteresis, operating voltage, and response time. Using a high birefringence liquid crystal mixture, we have improved the device contrast ratio while keeping low operating voltage, and fast response time. Potential applications of such a PSLC for light shutters, variable optical attenuators, and switchable polarizers are emphasized

High-contrast vertical alignment of lateral difluoro-terphenyl liquid crystals

A simple method for achieving high-contrast vertical alignment of lateral difluoro-terphenyl liquid crystals using buffed polyimide substrates is demonstrated. By doping a positive, nonpolar or negative dielectric anisotropic compound or mixture to the host terphenyl liquid crystals, an excellent vertical alignment is obtained. This alignment is stable throughout the entire nematic range. The selected dopants not only improve the contrast ratio but enhance the figure-of-merit of the host terphenyl mixture as well. This alignment method is particularly useful for high-contrast liquid crystal televisions

Tunable-focus flat liquid crystal spherical lens

A tunable-focus spherical lens using two flat substrates and inhomogeneous electric field over a homogeneous liquid crystal (LC) layer is demonstrated. The top flat substrate has an imbedded spherical indium-tin-oxide (ITO) electrode and the bottom has a planar ITO electrode on its inner surface. The inhomogeneous electric field generates a centrosymmetric gradient refractive index profile within the LC layer which causes the focusing behavior. The focal length of the LC lens can be tuned continuously from infinity to 0.6 m by the applied voltage

Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals

We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum with the one achieved without dopant. New interesting features, such as frequency modulation response of the device and a transmission spectrum with tunable attenuation on the short wavelength side of the widest bandgap, suggest a potential application of this device as a tunable all-in-fiber gain equalization filter with an adjustable slope. The tunability of the device is achieved by varying the amplitude and the frequency of the applied external electric field. The threshold voltage for doped and undoped liquid crystals in a silica capillary and in a glass cell are also measured as a function of the frequency of the external electric field and the achieved results are compared

Electro-optics of polymer-stabilized blue phase liquid crystal displays

Electro-optics of polymer-stabilized blue phase liquid crystal displays (BP LCDs) is analyzed and validated experimentally. A numerical model for characterizing and optimizing the electro-optical and display properties of BP LCDs in in-plane switching and fringe field switching cells is developed. The simulated voltage-dependent transmittance curves agree well with the measured results. To lower the operating voltage while keeping a high transmittance, both electrode width and gap, and large Kerr constant make important contributions. A wide-view BP LCD using a single biaxial compensation film is simulated

Negative A-plates for broadband wide-view liquid crystal displays

Negative A-plates fabricated by mechanically stretching polystyrene are studied and their physical properties evaluated. A molecular model is developed to explain the underlying physical mechanisms. An example of a broadband wide-view liquid crystal display including a negative A-plate for phase compensation is illustrated

Temperature effect on liquid crystal refractive indices

A model describing the temperature effect of liquid crystal (LC) refractive indices is derived and confirmed by experiment. Two single LC compounds (5CB, 5PCH) and two mixtures (MLC-6241-000 and UCF-35) with different birefringence values were used to validate the model. This model fits all the experimental data well. For a low-birefringence LC mixture, if the operating temperature is far below its clearing point, the temperature-dependent refractive indices can be approximated as a parabolic form. This prediction is also experimentally validated. In addition, a linear relationship between \u3c n(2) \u3e and temperature is found

Fast-response and scattering-free polymer network liquid crystals for infrared light modulators

A fast-response and scattering-free homogeneously aligned polymer network liquid crystal (PNLC) light modulator is demonstrated at lambda=1.55 m m wavelength. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. The strong polymer network anchoring assists LC to relax back quickly as the electric field is removed. As a result, the PNLC response time is; similar to250x faster than that of the E44 LC mixture except that the threshold voltage is increased by; similar to250x

Liquid Crystals Composition and Liquid Crystal Display With Patterned Electrodes

A liquid crystal composition and a display having the same are provided. The liquid crystal composition includes a first class including a highly conjugated liquid crystal compound and a second class including a highly polar compound. The second class includes a liquid crystal represented by Chemical Formula (I): R1-(CyOBO)-R2 Where R1 and R2 may be the same or different, and has an aromatic ring having at least one fluorine atom. The liquid crystal compound represented by Chemical Formula (I) is included at less than 75% by weight of the total content of the liquid crystal composition in one example. This invention relates to a liquid crystal composition and a display comprising the same. More specifically presented liquid crystal medium exhibits blue phase and is intended for polymer stabilized composites