A two-dimensional fluid simulation of Hg-Ne-Ar mixtures is developed for the study of flat fluorescent lamps (FFLs) for a backlight unit of a large-area liquid crystal display. The effects of control parameters, such as gas pressure, gap distance, driving voltage and frequency, and gas mixture ratio on discharge efficiency are investigated over the following parameter ranges: pressure of 10 -100 Torr, Hg ratio of 0.3 -2.0%, and driving voltage of 500 -2000 V with a driving frequency of 10 -100 kHz. In general, the luminance increases with driving voltage, Hg ratio, gas pressure, and the driving frequency. The luminance efficacy has optimal values for each parameter with proper steady state conditions for the enery loss mechanism and the creation and the transport of ultraviolet light.