플라즈마 소수성 코팅을 이용한 실리케이트계 황색형광체의 내구성 개선에 관한 연구

Hydrophobic coating on a silicate-based yellow phosphor () was carried out by using hexamethyldisiloxane (HMDSO) precursor in an atmospheric pressure dielectric barrier discharge plasma reactor, eventually to improve the long-term stability and reliability of the phosphor. The phosphor powder samples were characterized by a scanning electron microscope (SEM), a transmission electron microscope (TEM), a fluorescence spectrophotometer and a contact angle analyzer. After the coating was prepared, the contact angle of the phosphor powder increased to for water and to for glycerol, indicating that a hydrophobic layer was formed on its surface. The phosphor coated with HMDSO exhibited photoluminescence enhancement up to 7.8%. The SEM and TEM images of the phosphor powder revealed that the plasma coating led to a morphological change from grain-like structure to smooth surface with 31~46 nm thick hydrophobic layer. The light emitting diode (3528 1 chip LED) fabricated with the coated phosphor showed a substantial enhancement in the reliability under a special test condition at and 85% relative humidity for 1,000 h (85/85 testing). The plasma-mediated method proposed in this work may be applicable to the formation of 3-dimensional coating layer on irregular-shaped phosphor powder, thereby improving the reliability.