FILM FORMATION MECHANISM OF POLYMER AND PIGMENT CO-ELECTRODEPOSITION APPLIED TO THIN MICROCOLOR FILTER FABRICATION

Anodic electrodeposition (ED) of a polymer and an organic pigment on an indium tin oxide (ITO) transparent electrode has been investigated for fabrication of a thin microcolor filter applied to full color liquid crystal displays (LCDs). The waterborne polymer and the pigment are coagulated at the surface of ITO electrodes under the influence of protons, which are generated with electrolytic decomposition of water. The galvanostatic study confirms that the critical proton concentration, [formula omitted], is necessary for starting electrodeposition and is influenced by amine concentration in an electrodeposition bath. Also the difference in [formula omitted] between pigmented and unpigmented particles causes the dependence of pigment content in the final layer upon the applied voltage. The kinetic model of the constant voltage electrodeposition in the pigmented system is rationalized by combining two basic processes, one is the lateral coverage of electrode and the other the growth of the film thickness. Analysis of constant voltage electrodeposition proves that the thickness of the deposited film relating to the applied voltage and the time is expressed by introducing parameters of the kinetic model. The nature of the pigment strongly affects some of these parameters and, accordingly, causes the change in the thickness. Theoretical interpretation of some parameters is included. © 1990, The Electrochemical Society, Inc. All rights reserved.