In this study, we attempted to use TRITON TM X (or octyl phenol ethoxylate (OPE) of different oxyethylene units (i.e., n = 2, 5, and 10))-based dispersants containing a carboxylic group in the oxyethylene chain end for the formulation of BAM phosphor paste. Thus, a three-component system employing OPE-COOH as a dispersant, terpineol as a solvent, and ethyl cellulose as a binder was compounded with BAM particles, and the rheological properties of the paste were investigated in detail. Among three acidic TRITON X-based compounds we tested (i.e., [OPE2COOH], [OPE5-COOH], and [OPE10-COOH]), OPE10COOH containing the highest number of oxyethylene units in the backbone was found to be the dispersant showing the lowest viscosity of BAM paste under identical conditions. (c) 2007 Wiley Periodicals, Inc.