Method for producing selected alignment in liquid crystal

Abstract

Abstract A method of treating the surface of substrates used in liquid crystal display cells so that the surface forces the alignment of the liquid crystal layer to be either parallel with the substrate wall or perpendicular to it. The method includes the step of forming free radicals of either oxygen or fluorine in a radio frequency plasma and exposing the glass or tin doped indium oxide (ITO) substrate to the reaction products of the plasma in such a manner that electron or ion bombardment is avoided. When oxygen radicals only are employed, the surface forces parallel alignment. When the oxygen treatment is followed by exposure to fluorine free radicals, the surface forces perpendicular alignment. To provide strong parallel alignment in reflecting liquid crystal display cells having metal, glass or ITO surfaces, the method consists of producing an oxygen plasma as described above and introducing either a volatile organo-silicon or an organo tin compound into the plasma. The organo compound is completely oxidized in the plasma and the reaction product, SiO 2 or SnO 2 , is carried by the gas stream onto the substrate which is placed well outside the plasma region where it forms a thin coherent deposit on the metal. To provide strong perpendicular alignment in display cells having metal, glass or ITO surfaces, the method consists of the oxygen treatment followed by exposure to a fluorine free radical plasma formed from an unsaturated polyfluorinated compound. A polymeric film is formed on the substrate by the in situ polymerization of the active fluorine species in the plasma.

Inventors

• 👤 Roy Morris Gibson
• 👤 Gerard John Sprokel

Bibliographic Details