Light-emitting device including light-emitting diode and stacked light-emitting phosphor layers

US7897987B2 · kind B2 · utility

Assignee

• TOYODA GOSEI CO., LTD. · JP

Inventors

• Mitsuhiro Inoue · Osaka, JP
• Kenji Ito · Hino, JP
• Kazuyohi Tomita · Nagoya, JP
• Tetsu Kachi · Miyoshi, JP
• Takahiro Kozawa · Miyoshi, JP
• Satoru Kato · Ebeye, US
• Tadashi Ichikawa · Miyoshi, JP

Key dates

• Filing date: Mar 6, 2009
• Grant date: Mar 1, 2011
• Expiry date: Mar 6, 2029

Classification

• Technology area (CPC H): Electricity
• CPC primary: H01L2224/48091

Abstract

A light-emitting device includes a light-emitting diode, a red light-emitting phosphor layer, a yellow light-emitting phosphor layer, and a blue light-emitting phosphor layer. These layers are stacked in the stacking sequence of the yellow, blue, and red phosphor layers in order of increasing distance from the LED. The stacking sequence of the yellow and blue phosphor layers is first determined in such a manner that these layers do not interact with each other. The stacking sequence of the red and yellow phosphor layers and the stacking sequence of the red and blue phosphor layers are determined by the discriminant D. This determination of the stacking sequence suppresses a reduction in the conversion efficiency of the phosphors due to concentration quenching, improving the emission efficiency of the light-emitting device.