IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Organic Films and Devices Thursday Sessions
       Session OF+TF-ThM

Paper OF+TF-ThM2
XPS Characterization of Photo-Alignment of Liquid Crystals using Adsorbed Dichroic Materials

Thursday, November 1, 2001, 8:40 am, Room 131

Session: Characterization of Organic Thin Films
Presenter: L. Su, Kent State University
Authors: L. Su, Kent State University
J.L. West, Kent State University
Y. Reznikov, Ukraine Academy of Science
K. Artyushkova, Kent State University
J.E. Fulghum, Kent State University
Correspondent: Click to Email
The alignment layer is one of the most important parts of a twisted nematic (TN) display. Many methods exist for producing alignment, and the quality of the alignment layer directly influences the performance of the display. The most popular alignment method used by the Liquid crystal display (LCD) industry is mechanical rubbing of a polymer film. However, there are many disadvantages associated with this method, such as the introduction of dust particles, formation of electrostatic charges and other defects on the rubbed surface. Photo-alignment of liquid crystals is emerging as one of the most promising substitutes for mechanical rubbing. Photo-alignment generates surface anisotropy through the interaction between the irradiated substrate and the light source. Photo-alignment using adsorbed dichroic materials provides an efficient and versatile way to produce effective alignment of liquid crystals. Successful photo-alignment results from properly matching the adsorbed and substrate materials. In this study, poly(vinyl) alcohol (PVA) and adsorbed dichroic materials, including the dye Brilliant Yellow, are utilized as the alignment layer. We will demonstrate the use of polarized UV-Vis spectroscopy and angle-resolved x-ray photoelectron spectroscopy (XPS) for studying the interaction of the polymer, dye and liquid crystal. Using ARXPS, it is possible to study the distribution of all three organic layers. Both techniques indicate that intermolecular interaction between the adsorbed dichroic molecules and the substrate polymer is critical to the outcome of photoalignment. This work has been supported in part by NSF ALCOM (DMR 89-20147), and the Air Force (DAGSI SN-AFIT-9903).