Hydrophobic coating of silicate phosphor powder using atmospheric pressure dielectric barrier discharge plasma



A stable superhydrophobic coating was successfully deposited on commercial silicate-based orange phosphor by using atmospheric pressure dielectric barrier discharge plasma with hexamethyldisiloxane (HMDSO) and HMDSO/toluene mixture as precursors. Owning to the good optical properties, the deposited film acts not only as a hydrophobic protective layer but also as an antireflection optical thin film capable of improving the phosphor photoluminescence efficiency. The plasma-polymerized film based on Si[BOND]O[BOND]Si backbone containing methyl and phenyl nonpolar functional groups exhibited high-water-repellent characteristics. It was found that the water contact angle gradually increased with increasing the aging time and remained unchanged at about 140° after 1-month aging. Besides, the thermal stability of the coated phosphor under high-temperature condition was substantially enhanced by the aging. The findings of this work can contribute to improving the durability and reliability of the phosphor, eventually the long-term stability of phosphor-based light emitting diodes in practical applications. © 2014 American Institute of Chemical Engineers AIChE J, 60: 829–838, 2014