Thermally developable materials including photothermographic and thermographic materials have a buried conductive backside layer comprising one or more binder polymers in which are dispersed each of at least two types of conductive materials: (1) nanoparticles of one or more conductive metal compounds, and (2) one or more organic solvent soluble inorganic alkali metal salt antistatic compounds. These buried conductive backside coatings provide conductivity that is affected minimally by humidity.