26.2: Molecular Alignment in Crystal Polarizers and Retarders

Abstract

Optiva, Inc. has developed new technology for Thin Crystal Film (TCF) polarizers and retarders manufactured by deposition and drying of water-based lyotropic liquid crystal materials. An effective method to control and monitor two significant steps of this technology, a self-assembly into rod-like supramolecules in liquid material and its subsequent molecular alignment into TCF, is X-ray diffraction. There is direct correlation between X-ray data and the final optical characteristics of TCF polarizers and retarders and therefore its implementation into LCD applications.

Liquid Crystals: A Unique Phase of Matter

“…Planar polyaromatic precursors can be functionalized to introduce ionic groups at the periphery of the molecular disks [Iverson et al (2002); Fiske et al (2002)]; the disk edges become hydrophilic, while the polyaromatic faces remain hydrophobic. In an aqueous solution, the molecules stack face-to-face to provide favorable local environments for both face and edge groups.…”

“…There has been a lot of work on the applied front with these materials because of their potential as polarizers in displays. Further basic studies on these lyotropic discotic liquid crystal materials have better illuminated their structure [Lazarev and Paukshto (2001); Fiske et al (2002)] and rheological properties [Remizov et al (2001)]. …”

Translucent LCDs

“…We produced thin crystal films from the new clear materials by the method that we will refer to as Cascade Crystallization. [2][3][4][5][6] The Cascade Crystallization process involves a chemical modification step and four steps of ordering during the crystal film formation. The chemical modification step introduces hydrophilic groups on the periphery of the molecule in order to impart amphiphilic properties to the molecule.…”

“…[6][7][8] At certain concentration, supramolecules are converted into a liquidcrystalline state to form a lyotropic liquid crystal, which is the second step of ordering. The lyotropic liquid crystal is deposited under the action of a shear force (or meniscus force) onto a substrate based on a Mayer Rod or Slot-die coating technique, [2][3][4][5][6][9][10][11] so that the shear force (or the meniscus) direction determines the crystal axis direction in the resulting solid crystal film. This shear-force-assisted directional deposition is the third step of ordering, representing the global ordering of the crystalline or polycrystalline structure on the substrate surface.…”

“…The fourth step of the Cascade Crystallization process is drying/crystallization, which converts the lyotropic liquid crystal into a solid crystal film. 5,6 We will use the term Cascade Crystallization process to refer to the chemical modification and four ordering steps as a combined process. The Cascade Crystallization process is used for production of thin crystalline films (TCF) of Optiva's materials.…”