A Liquid Crystal Display Having a Rubbing-Free Photo-Aligned Monomolecular Layer as an Alignment Film

Twisted nematic (TN) type liquid crystal displays (LCDs) using a rubbing-free photo-aligned monomolecular layer as a liquid crystal (LC) alignment film have been developed for the first time. The photo-aligned monomolecular layer was formed by a chemical adsorption (CA) technique using a new chlorosilane-type surfactant. The new chlorosilane-type surfactant synthesized has a long straight hydrocarbon chain, a chalconyl group at the molecular end and a trichlorosilyl group at the other end. The surfactant reacted with the surfaces of a thin film transistor (TFT) array and a color filter by dehydrochlorination in a moisture-free organic solvent. The photo-aligned monomolecular layer was constructed with molecules which were cross-linked or polymerized at the chalconyl group and anchored to the surfaces via siloxane (–SiO–) covalent bonds. The molecules were aligned and cross-linked or polymerized by irradiation of polarized deep UV light. In this LCD, the liquid crystal molecules were aligned at the molecular level along the molecular alignment direction of the photo-aligned monomolecular layer. High durability was realized, because the monomolecular layer was anchored to the surfaces via covalent bonds and cross-linked (or polymerized). Low cost will also be realized, because as the monomolecular layer is aligned by means of non-contact rubbing-free technique, the yield of defect-free displays will be high.