Time multiplexed gray scale approach

A method of illuminating an active matrix electroluminescent device to provide a gray scale display, said device comprising a first electrode layer comprising an active matrix of individually addressable pixel electrodes, a second electrode layer, and a thin film electroluminescent laminate stack including at least a nongaseous electroluminescent phosphor layer which produces light upon the application of an electric field across the phosphor layer and a dielectric layer, said stack being disposed between said first and second electrode layers, comprising the steps of:

• (a) selecting a set of selected ones of said pixel electrodes with data signals during the first subframe time period of a frame;
• (b) driving said second electrode layer during said first subframe time period with a first illumination signal having predetermined characteristics including frequency, amplitude and wave shape to simultaneously illuminate all pixels within said nongaseous electroluminescent phosphor layer associated with said set of said selected ones of said pixel electrodes;
• (c) selecting at least one of said set of said selected ones of said pixel electrodes with data signals during a subsequent subframe time period of said frame;
• and
• (d) driving said second electrode layer during said subsequent subframe time period with an altered illumination signal wherein one or more of said predetermined characteristics differ from the first illumination signal to simultaneously illuminate all pixels within said nongaseous electroluminescent phosphor layer associated with said at least one of said set of said selected ones of said pixel electrodes.