LIGHT EMITTING DEVICE

• US 20130257266A1
• Filed: 11/08/2011
• Published: 10/03/2013
• Est. Priority Date: 12/09/2010
• Status: Active Grant

• Current Assignee: Citizen Electronics Company Limited
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ishizaki, Shinya
• Granted Patent: US 9,351,371 B2
• Time in Patent Office: Days
• US Class Current: 313/503
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: H05B 33/12 Light sources with substantially two-dimensional radiating surfaces

Abstract

Provided is a light emitting device in which with the general color rendering index Ra and the special color rendering index R9 maintained at high numeric values, the light emission efficiency is prevented from being reduced as much as possible, and the high color rendering and the high efficiency are achieved so as to be usable for general lighting usage. The device includes at least one light emitting element 6 emitting a light having a peak emission wavelength in a near-ultraviolet to blue region, and a phosphor layer 5 containing a green phosphor excited by a primary light emitted from the light emitting element 6 and emitting a light having a peak emission wavelength in a green region, a first red phosphor excited by the primary light and emitting a light having a peak emission wavelength in a red region, and a second red phosphor exited by the primary light and emitting a light having a peak emission wavelength different from that of the first red phosphor in the red region.

Claims

1. A light emitting device comprising:

at least one light emitting element emitting a light having a peak emission wavelength in a near-ultraviolet to blue region; and

a phosphor layer containing a green phosphor excited by a primary light emitted from the light emitting element and emitting a light having a peak emission wavelength in a green region, a first red phosphor excited by the primary light and emitting a light having a peak emission wavelength in a red region, and a second red phosphor exited by the primary light and emitting a light having a peak emission wavelength different from that of the first red phosphor in the red region.

2. The light emitting device according to claim 1, wherein

the peak emission wavelength of the green phosphor falls within a wavelength range of 510 nm or more and 550 nm or less,

the peak emission wavelength of the first red phosphor falls within a wavelength range of 610 nm or more and less than 625 nm, and

the peak emission wavelength of the second red phosphor falls within a wavelength range of 625 nm or more and 670 nm or less.

3. The light emitting device according to claim 1, wherein

the light emitting element is an LED chip emitting a light having a peak emission wavelength within a wavelength range of 350 nm or more and 490 nm or less.

4. The light emitting device according to claim 1, wherein

the light emitting element is an LED chip emitting a light having a peak emission wavelength within a wavelength range of 430 nm or more and 490 nm or less.

5. The light emitting device according to claim 1, wherein

the light emitting element is an LED chip emitting a light having a peak emission wavelength within a wavelength range of 350 nm or more and less than 430 nm, and

the phosphor layer further contains a blue phosphor excited by the primary light emitted from the light emitting element and emitting a light having a peak emission wavelength in a wavelength range of 430 nm or more and 490 nm or less.

6. The light emitting device according to claim 3, wherein the light emitting element is an InGaN series LED chip.

7. The light emitting device according to claim 1, wherein the green phosphor contains any one of an Al₅Lu_xO_y:

Ce series phosphor, a Ca₃(Sc, Mg)₂Si₃O₁₂;

Ce series phosphor, and an Al₅O₁₂Y₃;

Ce series phosphor.

8. The light emitting device according to claim 1, wherein each of the first and second red phosphors is a (Sr, Ca)AlSiN₃:

Eu series phosphor, or a CaAlSiN₃;

Eu series phosphor.

9. The light emitting device according to claim 1, wherein each weight allocation to total weight of the first and second red phosphors is adjusted so that a general color rendering index Ra shows that 80≦

Ra≦

97.

10. The light emitting device according to claim 9, wherein a weight ratio of the second red phosphor to the total weight of the first and second red phosphors is adjusted to be 25% or less so that the general color rendering index Ra shows that 80≦

Ra≦

85.

11. The light emitting device according to claim 9, wherein the weight ratio of the second red phosphor to the total weight of the first and second red phosphors is adjusted to be 25% or more and 75% or less so that the general color rendering index Ra shows that 85≦

Ra≦

90.

12. The light emitting device according to claim 9, wherein the weight ratio of the second red phosphor to the total weight of the first and second red phosphors is adjusted to be 75% or more so that the general color rendering index Ra shows that 90≦

Ra≦

97.

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

the phosphor layer is formed such that grains of the green phosphor, grains of the first red phosphor, and grains of the second red phosphor are mixed in a transparent resin, and

the light emitting element is sealed with the phosphor layer, or a transparent resin layer provided to be closer to the light emitting element than the phosphor layer and not containing a phosphor.

14. The light emitting device according to claim 1, wherein

the phosphor layer is formed to have a laminated structure composed of a green phosphor layer having grains of the green phosphor mixed in a transparent resin, a first red phosphor layer having grains of the first red phosphor mixed in a transparent resin, and a second red phosphor layer having grains of the second red phosphor mixed in a transparent resin, and

the light emitting element is sealed with a lowermost layer of the phosphor layer, or a transparent resin layer provided to be closer to the light emitting element than the phosphor layer and not containing a phosphor.

15. The light emitting device according to claim 1, wherein

the phosphor layer is formed to have a laminated structure composed of a green phosphor layer having grains of the green phosphor mixed in a transparent resin, and a red phosphor layer having grains of the first red phosphor and grains of the second red phosphor mixed in a transparent resin, and

the light emitting element is sealed with a lowermost layer of the phosphor layer, or a transparent resin layer provided to be closer to the light emitting element than the phosphor layer and not containing a phosphor.

16. The light emitting device according to claim 14, wherein the green phosphor layer is positioned above a layer in which the first red phosphor and the second red phosphor exist.

17. The light emitting device according to claim 13, wherein a median value of a grain diameter of the green phosphor is 8 μ

m or more and 20 μ

m or less.

18. The light emitting device according to claim 13, wherein a median value of a grain diameter of each of the first red phosphor and the second red phosphor is 5 μ

m or more and 15 μ

m or less.

19. The light emitting device according to claim 13, wherein the transparent resin of each layer of the phosphor layer is a silicone resin having a viscosity of 3 Pa˜

s or more and 20 Pa˜

s or less before being hardened.