Phosphor Conformal Coating by a Novel Spray Method for White Light-emitting Diodes as Applied to Liquid-crystal Backlight Module

Abstract

This work presents a novel pulsed spray process (PSP) for the conformal coating of yellow YAG:Ce(3+) phosphor on blue InGaN-based light emitting diodes (LEDs) for TFT-LCD backlight applications. This new approach exhibits much greater color spatial uniformity than conventional white LEDs coated with YAG phosphor by dispensing method. Unlike conformal coating by electrophorestic deposition (EPD), this new phosphor coating scheme of PSP represents an environmental friendly solution without Cr ion pollution. Additionally. PSP can be combined with an array blue chips on board (COB) in a manner that is compatible with large-area processing with high manufacture throughput, and can reduce the costs of TFT-LCD backlight applications.