Detlef Pauluth

Advanced liquid crystals for television

This review summarizes the diverse material requirements of the main Liquid Crystal Display (LCD) technologies used for televisions (TVs). We discuss recent advances in liquid crystal materials for this application. We highlight key materials and discuss synthesis, structure–property relations and LC mixture properties. For all technologies we have achieved fast switching LC mixtures (16 ms) and are en route to 8 ms thus improving the switching times for the next generation of superior performance LCD TVs.

Optimization of liquid crystals for television

Abstract— LCD TVs have dramatically improved in performance during the last 2 years. At the same time, the sale prices decreased by more than 50%. Together with the introduction of digital terrestrial broadcasting, this resulted in increasing sales of LCD TVs. This paper gives an overview of the main liquid-crystal display (LCD) technologies used for TVs. We discuss key materials, synthesis, structural property relationships, and the optimization of LC mixture properties. For all technologies, we have achieved fast-switching LC mixtures (16 msec). Novel materials for LC mixtures for the next generation of superior performance LCD TVs with 8-msec switching times are shown.

Combinatorial parallel synthesis and automated screening of a novel class of liquid crystalline materials

Combinatorial parallel synthesis has led to the rapid generation of a single-compound library of novel fluorinated quaterphenyls. Subsequent automated screening revealed liquid crystalline (LC) behaviour and gave qualitative relationships of molecular structures and solid state properties.

Novel liquid-crystal materials with negative dielectric anisotropy for TV application

— The development of materials for vertically aligned (VA) active-matrix display technology is briefly reviewed and the newest generation of liquid crystals for this application is disclosed. These new materials possess a unique combination of high dielectric anisotropy Δe and low rotational viscosity γ1 with good clearing temperatures TNI for fast-switching LC mixtures targeted for TV application.

23.1: Invited Paper: New Materials for Polymer-Stabilized Blue Phase

Compared to other liquid crystalline mesophases, the Blue Phase exhibits extremely fast switching via induced birefringence by an external field. However, the pure Blue Phase is characterized by a rather narrow temperature range on the order of a few K. For display applications, one very promising way to broaden the stable temperature range is achieved by polymer-stabilization of the Blue Phase. A crucial prerequisite for efficient stabilization is the optimal material selection/matching of reactive mesogens RMs and the chiral host. New material concepts will be introduced and discussed.

Integrated optical devices with liquid crystal overlays for the sensing of volatile organic compounds

We report the application of nematic liquid crystals for the optical sensing of organic solvents using two different evanescent field probes. Liquid crystals with different nematic ranges are used as sensitive coating materials on integrated optical reflection grating couplers and on integrated optical Mach-Zehnder interferometers as well. A non-linear behavior was observed when the liquid crystal coated IO transducers were exposed to various concentrations of toluene, meta-xylene and para-xylene. The calibration over a wide range pointed out a phase transition of the liquid crystal due to the penetration by the analyte. The birefringend liquid crystal and an isotropic polymer coating are compared by their responses to the xylene isomeres. The data indicate that the liquid crystals response is mainly given by a decrease of the order parameter S. Furthermore, we take advantage from the non-linearity and the clearing point in order to improve the performance of the sensor system.

Novel materials for polymer-stabilized blue phase

Blue phase shows one the fastest switching via induced birefringence by an external electrical field observed in liquid crystals. However, the pure blue phase typically has a narrow temperature range. Applying polymer-stabilization using reactive mesogens, a blue phase with a largely increased temperature range of up to 60 K can be obtained. Prerequisite for a good stabilization is the adequate matching of RMs and the optimized polymerization conditions. To achieve a low operating voltage of the polymer stabilised Blue phase display device, the material properties of the host - namely the product of the optical birefringence Δn and the electrical anisotropy Δε - has to be optimised. New host developments yielding a largely increased Δn * Δε ~ 40 at room temperature are presented.