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Display Forming Polymer/Liquid Crystal Composite Layers and Their Stability Against External Mechanical Distortions

: Bauer, M.; Hartmann, L.; Kuschel, F.; Seiler, B.; Noack, E.


Journal of applied polymer science 117 (2010), No.4, pp.1924-1933
ISSN: 0021-8995
ISSN: 1097-4628
Journal Article
Fraunhofer PYCO ()

The liquid crystal display (LCD) technology is confronted with the task to substitute rigid glass plates enclosing the electro-optically active liquid crystal (LC) material by plastic substrates. In particular, the commercialization of flexible displays requires a sufficient stabilization against external mechanical distortions. To achieve LC layer stabilization, several procedures have been suggested. In this work, the thermal-induced phase separation (TIPS) technique has been applied to generate composite films consisting of LC compartments which are encased by coherent polymer walls after binodal phase separation. Composite films were prepared from a series of poly(methacrylates) and various commercial nematic LC mixtures. Furthermore, the use of copolymers as well as binary blends from "hard" and "soft" poly(methacrylates) broadens the possibilities to control the film morphology. To compare different polymer/LC composite films regarding their stability under compression load, the samples were investigated by indentation tests using an inverse reflected-light microscope combined with a digital image acquisition technique. The deformation of the composite layers was evaluated by the uniDAC image analysis which relies on the more general method of Digital Image Correlation (DIC). Some of the fabricated composites show a remarkably high indentation resistance, especially such prepared from poly(1-tetralyl methacrylate) and poly(4-tert-butylcyclohexyl methacrylate). The results facilitate the selection of suitable composite systems for the fabrication of mechanically stabilized flexible LC displays.