Relationship between phosphor properties and chromaticity of phosphor-in-glass

SiO₂-B₂O₃-ZnO-Li₂O glass and four types of phosphors (Y₃Al₅O₁₂:Ce³⁺, (Sr,Ba)Si₂O₂N₂:Eu²⁺, CaAlSiN₃:Eu²⁺, and Lu₃Al₅O₁₂:Ce³⁺) with different spectral distributions and thermal properties were prepared to achieve the desired color point based on the relationship between the thermal properties of phosphors and the microstructure of the phosphor-in-glass (PIG). The glass frit was mixed with various contents of phosphors (2.5, 5.0, 7.5, and 10.0 vol%) and then sintered to form a PIG. It was confirmed that the different pore properties of each PIG, caused by the difference in phosphor thermal properties, have a strong influence on the optical properties of the PIG. As the mass change of the phosphor increases, the scattering coefficient of the PIG also increases based on the variations in both pore size and porosity inside the plate. It is apparent that the scattering coefficient is strongly related to the path of converted light and blue light from the light-emitting diode (LED) chip; therefore, the ratio of transmittance to reflectance of each PIG is different, even if each PIG has the same phosphor content. These results indicate that achieving the target LED chromaticity is closely related to the phosphor characteristics and PIG's pore properties.