Full color screen by EPD combined with photolithography for flat panel displays

Electrophoretic deposition (EPD) was employed for applying a phosphor coating for use in the fabrication of a full color screen consisting of red (R), green (G), and blue (B) phosphors. Patterned phosphor layers with a high packing density and uniformity can be fabricated by EPD combined with photolithography. For this process, R, G, and B phosphors were deposited on a patterned indium tin oxide glass by means of a commercial positive photoresist based on novolac resin and naphthoquinone diazide. The phosphor can be deposited on the patterned conductive substrate, but not on the surface of the photoresist film, because the photoresist has insulating properties. Conventional photolithographic conditions could not be used for this deposition because the commercial photoresist was soluble in the alcoholic solvent, which was used during the phosphor deposition. Instead, an insoluble photoresist was obtained by optimizing the baking temperature. Patterned color screens were studied using scanning electron microscopy and photoluminescence spectroscopy. The adhesion strength of the patterned color screens was substantially improved by the use of a coating of aqueous solution including polyvinyl alcohol and ammonium dichromate, followed by curing under UV light. (C) 2004 The Electrochemical Society.