A flat light source having a main region and an edge region around the main region is provided. The flat light source includes a first substrate, first electrodes, dielectric patterns, a phosphor layer, first phosphor patterns, a second substrate, and a sealant. The first electrodes are disposed on the first substrate and arranged within the main region and the edge region. The dielectric patterns cover the first electrodes. The phosphor layer is disposed between the dielectric patterns in the main region and the edge region. The first phosphor patterns are disposed on the phosphor layer within the edge region. The second substrate is disposed above the first substrate, and the sealant is formed out of the edge region between the first and second substrates so as to bond the two substrates.