We demonstrate for the first time a large-scale ac plasma display panel enhanced by localized surface plasmon (LSP) resonance owing to Ag nanoparticles. In order to generate plasmon resonance fitted to the blue-emitting phosphor, we deposited Ag nanoparticles on the phosphor layer by a spray method using large-scale fabrication technology. Localized surface plasmon resonance by Ag nanoparticles was strongly induced at the blue-emission regime. The measurement of the optical and electrical properties revealed that the enhanced emission from the phosphor was reflected in luminous efficacy enhanced by an average of 17.8% in manufactured test display panels. The improved luminous efficiency originated from the resonant coupling between the LSPs of the Ag nanoparticles and the electric-dipole transition of europium ions responsible for blue emission.