# US 9,518,215 B2 · Light-emitting device and light-emitting apparatus

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- Number: US 9,518,215 B2
- Document ID: US9518215B2
- Status: Granted
- Kind: B2
- Application number: 14/618,254
- Filed: 2015-02-10
- Published: 2015-09-03
- Granted: 2016-12-13
- Earliest claimed: 2014-02-28
- Assignees: Panasonic Intellectual Property Management Co., Ltd.
- Applicants: Panasonic Intellectual Property Management Co., Ltd.
- Inventors: Taku Hirasawa; Yasuhisa Inada; Yoshitaka Nakamura; Akira Hashiya; Mitsuru Nitta; Takeyuki Yamaki
- Web page: https://patentgrep.com/patent/US9518215B2

## CPC

- C09K 11/00: Luminescent materials, e.g. electroluminescent or chemiluminescent
- H05B 33/14: characterised by the chemical or physical composition or the arrangement of the electroluminescent material {, or by the simultaneous addition of the electroluminescent material in or onto the light source}
- H10H 20/8516: {having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer or wavelength conversion layer with a concentration gradient}
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS

## Abstract

A light-emitting device includes a photoluminescent layer that emits light containing first light, a light-transmissive layer located on or near the photoluminescent layer, and one or more reflectors. A submicron structure is defined on at least one of the photoluminescent layer and the light-transmissive layer. The one or more reflector are located outside the submicron structure. The submicron structure includes at least projections or recesses and satisfies the following relationship: λa/nwav-a<Dint<λa where Dint is a center-to-center distance between adjacent projections or recesses, λa is the wavelength of the first light in air, and nwav-a is the refractive index of the photoluminescent layer for the first light.

## Claims

### 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
one or more reflectors that are located directly on at least one of the photoluminescent layer and the light-transmissive layer, and at least partially surround the submicron structure, wherein
at least one of the photoluminescent layer and the light-transmissive layer has a submicron structure comprising at least projections or recesses arranged perpendicular to a 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 submicron structure satisfies the following relationship:
λa/nwav-a<Dint<λa
where Dint is a center-to-center distance between adjacent projections or recesses, λa is the wavelength of the first light in air, and nwav-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.

### Claim 2 (depends on 1)

The light-emitting device according to claim 1, wherein the one or more reflectors include at least one reflector comprising a reflective metal surface located on an end surface of the photoluminescent layer.

### Claim 3 (depends on 2)

The light-emitting device according to claim 2, further comprising a phase-matching element between the submicron structure and the reflective metal surface.

### Claim 4 (depends on 1)

The light-emitting device according to claim 1, wherein the one or more reflectors include at least one pair of reflectors that are arranged in a direction of a periodic pattern of the submicron structure in such a way that the submicron structure is located between the pair of reflectors.

### Claim 5 (depends on 1)

A light-emitting apparatus comprising:
the light-emitting device according to claim 1; and
a light source that directs excitation light into the light-emitting device.

### Claim 6 (depends on 1)

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

### Claim 7 (depends on 1)

The light-emitting device according to claim 1, wherein 380 nm≦λa≦780 nm is satisfied.

### Claim 8 (depends on 1)

The light-emitting device according to claim 1, wherein the thickness of the photoluminescent layer, the refractive index of the photoluminescent layer and the center-to-center distance 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.

### Claim 9 (depends on 1)

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

### Claim 10 (depends on 1)

The light-emitting device according to claim 1, wherein the directional angle is limited less than 15 degrees.

### Claim 11 (depends on 1)

The light-emitting apparatus according to claim 1, further comprising a substrate that has refractive index ns-a for the first light and is located on the photoluminescent layer, wherein λa/nwav-a<pa<λa/ns-a is satisfied.

### Claim 12 (depends on 1)

The light-emitting device according to claim 1, wherein the thickness of the photoluminescent layer, the refractive index of the photoluminescent layer and the center-to-center distance 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.

### Claim 13

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 having a higher refractive index than the photoluminescent layer; and
one or more reflectors that are located directly on at least one of the photoluminescent layer and the light-transmissive layer, and at least partially surround the submicron structure, wherein
the light-transmissive layer has a submicron structure comprising a periodic structure having at least projections or recesses arranged perpendicular to a thickness direction,
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 periodic structure satisfies the following relationship:
λa/nwav-a<pa<λa
where pa is the period of the periodic structure, λa is the wavelength of the first light in air, and nwav-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 period of the periodic structure are set to limit a directional angle of the first light emitted from the light emitting surface.

### Claim 14 (depends on 13)

The light-emitting device according to claim 13, wherein a distance between the submicron structure and the photoluminescent layer is more than λa/2.

### Claim 15

A light-emitting device comprising:
a light-transmissive layer having a submicron structure; a photoluminescent layer that has a first surface perpendicular to a thickness direction thereof and is located on the submicron structure and emits light containing first light; and
one or more reflectors that are located directly on the light-transmissive layer and, at least partially surround the submicron structure, wherein
at least one of the photoluminescent layer and the light-transmissive layer has a light emitting surface perpendicular to a thickness direction of the photoluminescent layer, the first light being emitted from the light emitting surface,
the submicron structure comprises a periodic structure having at least projections or recesses arranged perpendicular to the thickness direction,
the periodic structure satisfies the following relationship:
λa/nwav-a<pa<λa
where pa is the period of the periodic structure, λa is the wavelength of the first light in air, and nwav-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 period of the periodic structure are set to limit a directional angle of the first light emitted from the light emitting surface.

### Claim 16

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
one or more reflectors that are located directly on the photoluminescent layer, and at least partially surround the submicron structure, wherein
the photoluminescent layer has a submicron structure comprising a periodic structure having at least projections or recesses arranged perpendicular to a thickness direction of the photoluminescent layer,
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,
the periodic structure satisfies the following relationship:
λa/nwav-a<pa<λa
where pa is the period of the periodic structure, λa is the wavelength of the first light in air, and nwav-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 period of the periodic structure are set to limit a directional angle of the first light emitted from the light emitting surface.

### Claim 17

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 that is located on the photoluminescent layer, wherein
at least one of the photoluminescent layer and the light-transmissive layer has a submicron structure comprising at least projections or recesses arranged perpendicular to a thickness direction of the photoluminescent layer, and one or more distributed Bragg reflectors comprising at least projections or recesses arranged perpendicular to the thickness direction of the photoluminescent layer,
the one or more distributed Bragg reflectors at least partially surround the submicron structure,
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, and
the submicron structure satisfies the following relationship:
λa/nwav-a<Dint<λa
where Dint is a center-to-center distance between adjacent projections or recesses, λa is the wavelength of the first light in air, and nwav-a is the refractive index of the photoluminescent layer for the first light.

### Claim 18 (depends on 17)

The light-emitting device according to claim 17, wherein
the submicron structure comprises a periodic structure including the projections or recesses of the submicron structure,
the distributed Bragg reflector comprises a diffraction grating including at least the projections or recesses of the distributed Bragg reflector,
the periodic structure of the submicron structure has a first period, and
the diffraction grating of the distributed Bragg reflector has a second period that is one-half the first period.

### Claim 19 (depends on 17)

The light-emitting device according to claim 17, further comprising a phase-matching element between the submicron structure and the distributed Bragg reflector.

### Claim 20 (depends on 19)

The light-emitting device according to claim 19, wherein the periodic structure has a first period, the phase-matching element having a length that is one-eighth the first period.