Improvement in the color uniformity of LED by microspheres generated from phase separation

In this study, we generated microspheres of silicone-encapsulated epoxy by mixing heterogeneous liquid silicone and epoxy with different polarities in order to reduce the deviation of color temperature with variations in the viewing angle of light-emitting diodes (LEDs). The diameter of the microspheres, measured with an optical microscope, ranged from 2 μm to 7 μm, and the microspheres did not stick to one another or become deposited within the silicone encapsulant. The viewing angle changed depending on the amount of epoxy material added. The addition of epoxy at 0.7 wt.% drastically increased the viewing angle from 77° (with no epoxy) to 111°. The mixing of phosphors with microspheres improved the uniformity of the color temperature of LED light sources, as the deviation in color temperature with the variation of the viewing angle was 80 K with 1 wt.% microsphere (epoxy) addition, suggesting high uniformity.

► Microspheres were generated from silicone-encapsulated epoxy by mixing heterogeneous liquid silicone and epoxy.
► Microspheres reduce the deviation of color temperature with variations in the viewing angle of light-emitting diodes.
► The addition of epoxy at 0.7 wt.% drastically increased the viewing angle from 77° (with no epoxy) to 111°.
► The mixing of phosphors with microspheres improved the uniformity of the color temperature of LED light sources.
► Epoxy microspheres in this study did not affect the reliability under high-temperature driving conditions.