Patent ID: 9618697
Date: 2017-04-11
CPC Classifications: G02B,H01L

Claim:
1. A light-emitting device comprising: a photoluminescent layer that has a first surface perpendicular to a thickness direction thereof and emits light containing first light, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface; a light-transmissive layer located on the photoluminescent layer; and a low-refractive-index layer located on the photoluminescent layer so that the photoluminescent layer is located between the low-refractive-index layer and the light-transmissive layer, the low-refractive-index layer having a lower refractive index than the photoluminescent layer, wherein at least one of the photoluminescent layer and the light-transmissive layer has a first submicron structure comprising at least projections or recesses arranged perpendicular to the thickness direction of the photoluminescent layer, at least one of the photoluminescent layer and the light-transmissive layer has a light emitting surface perpendicular to the thickness direction of the photoluminescent layer, the first light being emitted from the light emitting surface, the first submicron structure satisfies the following relationship: where D int is a center-to-center distance between adjacent projections or recesses, λ a is the wavelength of the first light in air, and n wav-a is the refractive index of the photoluminescent layer for the first light, and a thickness of the photoluminescent layer, the refractive index of the photoluminescent layer, and the center-to-center distance are set to limit a directional angle of the first light emitted from the light emitting surface, the light-emitting device further comprises a high-refractive-index layer located on the low-refractive-index layer so that the low-refractive-index layer is located between the high-refractive-index layer and the photoluminescent layer, the high-refractive-index layer having a higher refractive index than the low-refractive-index layer, wherein the first submicron structure comprises the projections and recesses, the high-refractive-index layer has a lower refractive index than the photoluminescent layer, and the light-emitting device satisfies the following relationship: where m is a natural number, h p is the height of the first submicron structure, n p is the refractive index of the first submicron structure, f is the ratio of the volume of the projections to the sum of the volumes of the projections and the recesses in the first submicron structure, n W is the refractive index of the photoluminescent layer, and t W is the thickness of the photoluminescent layer.