Light-emitting apparatus including photoluminescent layer

• US 9,890,912 B2
• Filed: 07/20/2016
• Issued: 02/13/2018
• Est. Priority Date: 02/28/2014
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Hashiya, Akira, Hirasawa, Taku, Inada, Yasuhisa, Nakamura, Yoshitaka, Nitta, Mitsuru, Yamaki, Takeyuki
• Primary Examiner(s): Vu, Vu A
• Application Number:
  US15/214,837
• Publication Number:
  US 20160327219A1
• Time in Patent Office: 573 Days
• Field of Search: 257 98
• CPC Class Codes: F21K 9/64 using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
• CPC Class Codes: F21S 2/00 Systems of lighting devices, not provided for in main groups F21S4/00 - F21S10/00 or F21S19/00, e.g. of modular construction
• CPC Class Codes: G02B 5/1809 with pitch less than or comparable to the wavelength
• CPC Class Codes: G02B 5/1861 Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G02B 6/0003 the light guides being doped with fluorescent agents
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material
• CPC Class Codes: H01L 33/58 Optical field-shaping elements

Abstract

A light-emitting apparatus includes a light-emitting device and an excitation light source. The light-emitting device includes a photoluminescent layer, a light-transmissive layer. At least one of the photoluminescent layer and the light-transmissive layer has a submicron structure having at least projections or recesses. Light emitted from the photoluminescent layer includes first light having a wavelength λ_a in air. The distance D_int between adjacent projections or recesses and the refractive index n_wav-a of the photoluminescent layer for the first light satisfy λ_a/n_wav-a<D_int<λ_a. A thickness of the photoluminescent layer, the refractive index n_wav-a, and the distance D_int are set to limit a directional angle of the first light emitted from the light emitting surface. The excitation light source emits excitation light. The light-emitting device is integrally provided with the excitation light source.

Claims

1. A light-emitting apparatus comprising a light-emitting device and an excitation light source, wherein

the excitation light source is integrally provided with the light-emitting device and emits excitation light, and

the light-emitting device includes:

a photoluminescent layer having a first surface perpendicular to a thickness direction thereof, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface; and

a light-transmissive layer located on the photoluminescent layer, wherein

at least one of the photoluminescent layer and the light-transmissive layer has a submicron structure having at least projections or recesses arranged perpendicular to the thickness direction of the photoluminescent layer,

the photoluminescent layer receives the excitation light and emits light including first light having a wavelength λ

_a in air,

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,

a distance D_int between adjacent projections or recesses and a refractive index n_wav-a of the photoluminescent layer for the first light satisfy λ

_a/n_wav-a<

D_int<

λ

_a, and

a thickness of the photoluminescent layer, the refractive index n_wav-a, and the distance D_int are set to limit a directional angle of the first light emitted from the light emitting surface.

2. The light-emitting apparatus according to claim 1, wherein the submicron structure includes at least one periodic structure comprising the projections or recesses, and the at least one periodic structure includes a first periodic structure having a period p_a that satisfies λ

_a/n_wav-a<

p_a<

λ

_a.

3. The light-emitting apparatus according to claim 1, wherein

the light-emitting device further includes a low-refractive-index layer between the photoluminescent layer and the excitation light source and between the light-transmissive layer and the excitation light source, and

the low-refractive-index layer has a lower refractive index for the first light than the photoluminescent layer.

4. The light-emitting apparatus according to claim 3, wherein the low-refractive-index layer has second projections facing the excitation light source.

5. The light-emitting apparatus according to claim 1, wherein a light output side of the excitation light source is in direct contact with the photoluminescent layer or the light-transmissive layer.

6. The light-emitting apparatus according to claim 3, wherein a light output side of the excitation light source is in direct contact with the low-refractive-index layer.

7. The light-emitting apparatus according to claim 1, wherein the light-emitting device further includes a selective reflective layer that selectively reflects light passing through the photoluminescent layer.

8. The light-emitting apparatus according to claim 1, wherein the photoluminescent layer is in contact with the light-transmissive layer.

9. The light-emitting apparatus according to claim 1, wherein the submicron structure has both the projections and the recesses.

10. The light-emitting apparatus according to claim 1, wherein the photoluminescent layer includes a phosphor.

11. The light-emitting apparatus according to claim 1, wherein 380 nm≦

λ

_a≦

780 nm is satisfied.

12. The light-emitting apparatus according to claim 1, wherein the thickness of the photoluminescent layer, the refractive index n_wav-a, and the distance D_int are set to allow an electric field to be formed in the photoluminescent layer, in which antinodes of the electric field are located in areas, the areas each corresponding to respective one of the projections and/or recesses.

13. The light-emitting apparatus according to claim 1, wherein the light-transmissive layer is located indirectly on the photoluminescent layer.

14. The light-emitting apparatus according to claim 1, wherein the thickness of the photoluminescent layer, the refractive index n_wav-a, and the distance D_int are set to allow an electric field to be formed in the photoluminescent layer, in which antinodes of the electric field are located at, or adjacent to, at least the projections or recesses.

15. The light-emitting apparatus according to claim 1, wherein the light-emitting device further includes a substrate that has a refractive index n_s-a for the first light and is located on the photoluminescent layer, wherein λ

_a/n_wav-a<

D_int<

λ

_a/n_s-a is satisfied.

16. A light-emitting apparatus comprising a light-emitting device and an excitation light source, wherein

the excitation light source is integrally provided with the light-emitting device and emits excitation light, and

the light-emitting device includes:

a light-transmissive layer having a submicron structure; and

a photoluminescent layer that is located on the submicron structure and emits light in response to the excitation light, wherein

the photoluminescent layer has a first surface perpendicular to a thickness direction thereof, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface,

the light emitted from the photoluminescent layer includes first light having a wavelength λ

_a in air,

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 submicron structure includes at least one periodic structure comprising at least projections or recesses arranged perpendicular to the thickness direction of the photoluminescent layer,

a refractive index n_wav-a of the photoluminescent layer for the first light and a period p_a of the at least one periodic structure satisfy λ

_a/n_wav-a<

p_a<

λ

_a, and

a thickness of the photoluminescent layer, the refractive index n_wav-a, and the period p_a are set to limit a directional angle of the first light emitted from the light emitting surface.

17. A light-emitting apparatus comprising a light-emitting device and an excitation light source, wherein

the excitation light source is integrally provided with the light-emitting device and emits excitation light, and

the light-emitting device includes:

a photoluminescent layer emitting light in response to the excitation light; and

a light-transmissive layer that has a higher refractive index than the photoluminescent layer, and has a submicron structure, wherein the light emitted from the photoluminescent layer includes first light having a wavelength λ

_a in air,

the photoluminescent layer has a first surface perpendicular to a thickness direction thereof, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface,

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 submicron structure includes at least one periodic structure comprising at least projections or recesses arranged perpendicular to the thickness direction of the photoluminescent layer,

a refractive index n_wav-a of the photoluminescent layer for the first light and a period p_a of the at least one periodic structure satisfy λ

_a/n_wav-a<

p_a<

λ

_a, and

a thickness of the photoluminescent layer, the refractive index n_wav-a, and the period p_a are set to limit a directional angle of the first light emitted from the light emitting surface.

18. A light-emitting apparatus comprising a light-emitting device and an excitation light source, wherein

the excitation light source is integrally provided with the light-emitting device and emits excitation light,

the light-emitting device includes a photoluminescent layer emitting light in response to the excitation light, and has a submicron structure,

the photoluminescent layer has a first surface perpendicular to a thickness direction thereof, an area of the first surface being larger than a sectional area of the photoluminescent layer perpendicular to the first surface,

the submicron structure includes at least one periodic structure comprising at least projections or recesses arranged perpendicular to the thickness direction of the photoluminescent layer,

the light emitted from the photoluminescent layer includes first light having a wavelength λ

_a in air,

the photoluminescent 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,

a refractive index n_wav-a of the photoluminescent layer for the first light and a period p_a of the at least one periodic structure satisfy λ

_a/n_wav-a<

p_a<

λ

_a, and

a thickness of the photoluminescent layer, the refractive index n_wav-a, and the period p_a are set to limit a directional angle of the first light emitted from the light emitting surface.