Forming defect control of phosphor in glass color filters by single-step Isobam gel casting for DLP projectors

Due to the high-speed rotation and strong light exposure of digital light processing (DLP) projectors, the traditional polymer color wheel is at risk of deformation and color fading. Therefore, phosphor in glass (PiG) color filters will become a more heat-resistant alternative. In this work, we developed a single-step Isobam gel casting strategy that simultaneously forms green body with orange-red, green and transparent regions within a single mold, which avoided the need for subsequent stacking or gluing. In addition, the density of the green body was also increased by optimizing the solid content of the slurry. To suppress macroscopic defects that occur during molding, we first optimized the casting and demolding processes, obtaining green bodies with complete shapes and clear interfaces. Then the sintering system was optimized, and the following sintering system was finally determined. The temperature rises slowly from room temperature to 800 °C at a rate of 1 °C/min, and then cools along with the furnace chamber. During the cooling stage, residual stress is effectively released through slow temperature reduction, ensuring that the sample remains intact and free of cracks, and achieving defect control during forming stage.