Light-emitting device including photoluminescent layer

• US 10,012,780 B2
• Filed: 07/21/2016
• Issued: 07/03/2018
• 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: Inada, Yasuhisa, Hirasawa, Taku, Nitta, Mitsuru, Hashiya, Akira, Yamaki, Takeyuki
• Primary Examiner(s): Truong, Bao Q
• Application Number:
  US15/215,592
• Publication Number:
  US 20160327715A1
• Time in Patent Office: 712 Days
• 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 6/0035 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0058 varying in density, size, shape or depth along the light guide
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• CPC Class Codes: G02B 6/0085 Means for removing heat created by the light source from the package heat extraction or cooling elements for semiconductor light sources in general H01L33/64
• CPC Class Codes: G03B 21/204 using secondary light emission, e.g. luminescence or fluorescence using different colours G03B33/00; if related to video signals H04N9/3197
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/58 Optical field-shaping elements

Abstract

A light-emitting device includes a photoluminescent layer and a light-transmissive layer located on the photoluminescent layer. 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. At least one of the photoluminescent layer and the light-transmissive layer has a light emitting surface. The first light has a wavelength λ_a in air. 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. 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.

Claims

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; 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,

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 light has a wavelength λ

_a in air,

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 device according to claim 1, wherein the wavelength λ

_a of the first light is different from a peak wavelength of the light emitted from the photoluminescent layer in air.

3. The light-emitting device according to claim 1, wherein the refractive index n_t-a of the light-transmissive layer for the first light is lower than the refractive index n_wav-a of the photoluminescent layer for the first light.

4. The light-emitting device according to claim 1, wherein the first light has maximum intensity in a first direction determined in advance by the submicron structure.

5. The light-emitting device according to claim 4, wherein the first direction is normal to the photoluminescent layer.

6. The light-emitting device according to claim 4, wherein the first light emitted in the first direction is linearly polarized light.

7. The light-emitting device according to claim 4, wherein the directional angle of the first light with respect to the first direction is less than 15 degrees.

8. The light-emitting device according to claim 4, wherein second light having a wavelength λ

_b different from the wavelength λ

_a of the first light has maximum intensity in a second direction different from the first direction.

9. The light-emitting device according to claim 1, wherein the light-transmissive layer has the submicron structure.

10. The light-emitting device according to claim 1, wherein the photoluminescent layer has the submicron structure.

11. The light-emitting device according to claim 1, wherein

the photoluminescent layer has a flat main surface, and

the light-transmissive layer is located on the flat main surface of the photoluminescent layer and has the submicron structure.

12. The light-emitting device according to claim 11, wherein the photoluminescent layer is supported by a transparent substrate.

13. The light-emitting device according to claim 1, wherein

the light-transmissive layer is a transparent substrate having the submicron structure on a main surface thereof, and

the photoluminescent layer is located on the submicron structure.

14. The light-emitting device according to claim 1, wherein the refractive index n_t-a of the light-transmissive layer for the first light is higher than or equal to the refractive index n_wav-a of the photoluminescent layer for the first light, and each of the projections or recesses in the submicron structure has a height or depth of 150 nm or less.

15. The light-emitting device according to claim 1, wherein the submicron structure includes at least one periodic structure comprising at least 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.

16. The light-emitting device according to claim 1, wherein

the submicron structure includes at least one periodic structure comprising at least 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, and

the first periodic structure is a one-dimensional periodic structure.

17. The light-emitting device according to claim 16, wherein

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

_b different from the wavelength λ

_a in air,

the at least one periodic structure further includes a second periodic structure having a period p_b that satisfies λ

_b/n_wav-b<

P_b<

λ

_b, wherein n_wav-b denotes a refractive index of the photoluminescent layer for the second light, and

the second periodic structure is a one-dimensional periodic structure.

18. The light-emitting device according to claim 1, wherein the submicron structure includes a two-dimensional periodic structure having at least two periodic structures comprising at least the projections or recesses, and the at least two periodic structures have periodicity in different directions.

19. The light-emitting device according to claim 1, wherein

the submicron structure includes periodic structures comprising at least the projections or recesses, and

the periodic structures include periodic structures arranged in a matrix.

20. The light-emitting device according to claim 1, wherein

the submicron structure includes periodic structures comprising at least the projections or recesses, and

the periodic structures include a periodic structure having a period p_ex that satisfies λ

_ex/n_wav-ex<

P_ex<

λ

_ex, wherein λ

_ex denotes the wavelength of excitation light in air for a photoluminescent material contained in the photoluminescent layer, and n_wav-ex denotes the refractive index of the photoluminescent layer for the excitation light.

21. A light-emitting device comprising

photoluminescent layers and light-transmissive layers,

wherein at least two of the photoluminescent layers are independently the photoluminescent layer according to claim 1, and at least two of the light-transmissive layers are independently the light-transmissive layer according to claim 1.

22. The light-emitting device according to claim 21, wherein the photoluminescent layers and the light-transmissive layers are stacked on top of each other.

25. A light-emitting apparatus comprising:

the light-emitting device according to claim 1; and

an excitation light source irradiating the photoluminescent layer with excitation light.

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

29. The light-emitting device according to claim 1, wherein 380 nm≤

λ

_a≤

780 nm is satisfied.

30. The light-emitting device 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.

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

32. The light-emitting device 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.

33. The light-emitting device according to claim 1, further comprising 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.

23. A light-emitting device comprising:

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; and

at least one of the photoluminescent layer and the light-transmissive layer has a submicron structure extending perpendicular to the thickness direction of the photoluminescent layer,

wherein the photoluminescent layer emits light to form a quasi-guided mode in the photoluminescent layer and the light-transmissive layer.

24. A light-emitting device comprising:

a waveguide layer that has a periodic structure and contains a photoluminescent material, wherein

a quasi-guided is formed in the waveguide layer and

light emitted from the photoluminescent material is guided while interacting with the periodic structure in the quasi-guided mode.

26. 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; 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,

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, a wavelength λ

_ex of excitation light in air for a photoluminescent material contained in the photoluminescent layer, and a refractive index n_wav-ex of a medium having the highest refractive index for the excitation light out of media present in an optical path to the photoluminescent layer or the light-transmissive layer satisfy λ

_ex/n_wav-ex<

D_int<

λ

_ex, and

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

27. The light-emitting device according to claim 26, wherein the submicron structure includes at least one periodic structure comprising at least the projections or recesses, and the at least one periodic structure includes a first periodic structure having a period P_ex that satisfies λ

_ex/n_wav-ex<

P_ex<

λ

_ex.