Development of Phosphor film for Ultra-thin, High-brightness LCDs

In recent years, mini-LEDs and local dimming have been used in direct-type backlight units (BLUs) in LCDs to realize thinner LCD designs and higher contrast, so as to compete with OLEDs. A phosphor film with a green-emitting SrGa 2 S 4 :Eu phosphor, red-emitting K 2 SiF 6 :Mn phosphor and dichroic filter was developed and commercialized and is described in this paper. An LCD with a phosphor film and blue mini-LEDs in a direct-type BLU can realize a thinner design, higher contrast, higher luminance and higher uniformity. A smaller particle size is required for the SrGa 2 S 4 :Eu phosphor to improve the uniformity of the phosphor film, but the fluorescence of the phosphor tends to degrade during aging. A new surface coating for the SrGa 2 S 4 :Eu phosphor was found to improve its reliability.