Cees Bastiaansen

Polymer-Filled Nematics: A New Class of Light-Scattering Materials for Electro-Optical Switches

A new class of mixts. of liq. crystal materials and polymers is presented consisting of sub-micrometer sized, internally crosslinked polymeric particles dispersed in a continuous LC phase, which is referred to as polymer-filled nematics (PFNs) to distinguish them from LC mixts. contg. inorg. particles. Initial electrooptical expts. indicate that the light-scattering properties of these blends can be controlled with the application of an elec. field and that hysteresis effects are present. [on SciFinder (R)]

45.3: Micro-structured Polymeric Linearly Polarized Light Emitting Lightguide for LCD Illumination

A new linearly polarized light emitting lightguide system is presented, consisting of a micro-structured anisotropic polymer film which is coated with an isotropic layer and adhered to a transparent polymeric substrate. With conventional edge-lighting of the lightguide very high polarized contrasts are realized, exceeding 100. A gain in efficiency can be achieved by recycling of the trapped light with the orthogonal polarization.

CHAPTER 7:Light‐actuated Artificial Cilia Based on Liquid Crystal Networks

The use of liquid crystal networks (LCNs) for trigger-driven cilia combines control over the deformation direction with a large work potential. Photopolymerization of mesogenic monomers in their nematic phase leads to well-ordered densely cross-linked, glassy polymers which can be structured into small cilia attached to a substrate. The fabrication of the cilia is compatible with standard micro-fabrication techniques such as lithography and printing. These techniques allow control of the molecular orientation both in the plane and into the third dimension through the thickness of the film. Patterned films can be created with various orientation patterns of the network molecules. The geometry change of the cilia is driven by small decreases in molecular order. Besides their response to heat and chemical agents the LCN cilia can be engineered to respond to light. Cilia with a splayed or twisted nematic director profile show large out-of-plane bending, amplifying the small in-plane deformations. Photo-responsive responsive cilia with these alignments show fast deformation kinetics and large, reversible responses. With a micro-fluidic application in mind, an example of inkjet-printed cilia is given here. The cilia have subunits that can be selectively driven by changing the wavelength of the light trigger. The example shows the ability to miniaturize these systems and the versatility of the LCNs.

Novel liquid crystal displays based on highly polarized photoluminescent polymer films

Since the early 90s, much research has focused on the photoluminescence (PL) and electroluminescence (EL) properties of conjugated polymers, because of their potential application as emitting layer in EL devices. The introduction of uniaxial molecular orientation into films of luminescent polymers was naturally found to yield structures that emit polarized light. Rather surprisingly, the photoluminescence properties of oriented, conjugated polymers have attracted substantially less attention, especially from an application point of view. In this paper the authors report the fabrication of highly-polarized photoluminescent polymer films based on poly(2,5-dialkoxy-p-phenyleneethynylene)s (PPE), and their use in a new family of liquid crystal displays (LCDs). As one relevant example, a back-lit twisted-nematic configuration of an LCD was built, in which one of the absorbing polarizers was replaced by a polarized PL film, characterized by a dichroic ratio in excess of 70. Such devices can exhibit a substantial improvement in brightness, contrast and viewing angle, since the polarized photoluminescent films can combine two separate features, i.e., the functions of a polarizer and an efficient color filter.