Photopolymerization of polymer-coated solid substrates with linearly polarized light is shown to induce an anisotropic, uniaxial orientation of polymer molecules. The linearly photopolymerized (LPP) layers exhibit UV dichroism and optical anisotropy. The resulting anisotropic dispersive surface interaction forces are shown to align adjacent liquid crystals parallel. A qualitative microscopic model is presented. The new LPP-alignment technique allows to generate homogeneous LC-director pattern with different azimuthal director angles on the same substrate requiring no mechanical treatment. The use of LPP substrates in liquid crystal displays (LCDs) is shown to enable to combine different electrooptical effects-such as twisted nematic (TN) and parallel configurations-in the same hybrid LCD. Besides from high-contrast LPP-aligned TN-LCDs, LPP-aligned supertwisted nematic (STN)-LCDs exhibiting steep transmission-voltage characteristics are presented.

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A new electro-optical effect in twisted nematic liquid crystals is described which allows variation of the rotation of linearly polarized light continuously from 0° to 90°. It requires lower voltages than other electro-optic effects.

▪ Abstract  Since the early 1970s, three major prerequisites have brought the success of the liquid crystal display (LCD) technology to its key role of today. Namely, the discovery of electro-optical field-effects on which the displays are based, the successful search for liquid crystals (LCs) with material properties that meet the complex requirements of electro-optical effects and render the effects applicable in displays, and last but not least, the development of the technological tools required for manufacturing displays. Virtually all of today's commercial LCDs are based on the twisted nematic (TN) or on various supertwisted nematic (STN) effects whose extensive development and improvement over the past 25 years is still rapidly progressing. Those liquid crystal material properties and electro-optical effects that essentially determine the performance of nematic displays are reviewed. Correlations between molecular functional structural groups, LC material properties, and their electro-optical relevance for TN and STN displays are outlined. Included are dual-frequency addressing phenomena in liquid crystal materials, in situ dielectric heating of displays, and conductivity phenomena that are related and that may either hamper or improve the performance of high-information content LCDs. Moreover, we review some recent developments made in our laboratories on novel electro-optical devices and device-specific functional organic materials, e.g. optical alignment of monomeric and polymeric liquid crystals by linearly polarized light; the generation of photo-patterned multidomain twisted nematic displays with broad field of view; the operation of displays with circularly polarized light, as well as compact and bright cholesteric LCD projection optics whose polarizers, filters, and modulators are all based on liquid crystal elements.

Novel liquid-crystal devices are described that generate linearly polarized light with axial symmetry; the beam propagation axis is the symmetry axis. Such light fields can be characterized by a polarization order number P. For example, P = 1 fields represent radially or azimuthally polarized light. The reorientation of the polarization orientation in these polarization converters is due to the twisted nematic effect and the effect of lambda/2 wave plates. A single polarization converter can generate fields of orders 1 and 2. It is shown that one can in principle generate fields of any integral order P by cascading such elements. Devices that generate P = 1 fields are achromatic and can be used as polarization axis finders or as versatile tools for studying birefringent or polarizing materials.