Phosphor mixture and light emitting device

• US 20060197432A1
• Filed: 08/08/2005
• Published: 09/07/2006
• Est. Priority Date: 03/01/2005
• Status: Active Grant

• Current Assignee: Citizen Electronics Company Limited
• Original Assignee: Dowa Mining Company Limited (DOWA Holdings Company Limited)
• Inventors: Gotoh, Masahiro, Nagatomi, Akira, Sakane, Kenji
• Granted Patent: US 7,477,009 B2
• Time in Patent Office: Days
• US Class Current: 313/487
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3852 Nitrides, e.g. oxynitrides, carbonitrides, oxycarbonitrides, lithium nitride, magnesium nitride
• CPC Class Codes: C04B 2235/3865 Aluminium nitrides
• CPC Class Codes: C04B 2235/3873 Silicon nitrides, e.g. silicon carbonitride, silicon oxynitride
• CPC Class Codes: C04B 35/581 based on aluminium nitride
• CPC Class Codes: C04B 35/584 based on silicon nitride
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48257 connecting the wire to a die pad of the item
• 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 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials

Abstract

To provide a phosphor mixture realizing a light emitting device having a phosphor and a light emission element, by which light emission is performed, with a small color shift due to a feeding current and having an excellent color rendering properties. CaAlSin3:Eu as a red phosphor and YAG:Ce as a yellow phosphor are manufactured, and emission spectra thereof are obtained. Meanwhile, the emission spectrum of an excitation light emitted by a light emitting part is obtained. From the emission spectra thus obtained, a relative mixing ratio of each phosphor is obtained by simulation, so that a correlated color temperature of the light emitting device becomes a target temperature. Then, based on the relative mixing ratio thus obtained, each phosphor is measured and mixed, and a phosphor mixture is thereby obtained.

Claims

1. A phosphor mixture, which emits a visible light under an excitation of an excitation light of ultraviolet to green color, wherein under the excitation of the excitation light with a wavelength range from 430 nm to 500 nm, a peak value of a relative emission intensity at the temperature of 25°

C. is defined as P₂₅, and the peak value of the relative emission intensity at the temperature of T°

C. is defined as P_T, and when the value of T is changed in a range from 25°

C. to 200°

C., the value of (100×

(P₂₅×

P_T)/P₂₅) is within ±

25.

2. The phosphor mixture according to claim 1, comprising:

a phosphor which is given as a composition formula expressed by MmAaBbOoNn;

Z, (where element M is more than one kind of element having bivalent valency, element A is more than one kind of element having tervalent valency, element B is more than one kind of element having tetravalent valency, O is oxygen, N is nitrogen, and element Z is more than one kind of element acting as an activator, satisfying m=a=b=1, o<

0.5, n=3−

⅔

o); and

more than one kind of phosphor having an emission spectrum with an emission peak in the wavelength range from 500 nm to 630 nm when excited by ultraviolet to green excitation light.

3. The phosphor mixture according to claim 2, wherein

the element M is more than one kind of element selected from the group consisting of Ca, Mg, Sr, Ba, and Zn;

the element A is more than one kind of element selected from the group consisting of Al, and Ga;

the element B is more than one kind of element selected from the group consisting of Si and Ge; and

the element Z is more than one kind of element selected from rare earth elements and transitional metal elements.

4. The phosphor mixture according to claim 3, wherein the element Z is Eu.

5. The phosphor mixture according to claim 2, wherein the phosphor expressed by the composition formula MmAaBbOoNn:

Z is the phosphor having the composition formula CaAlSiN₃;

Eu.

6. The phosphor mixture according to claim 2, wherein the phosphor having an emission spectrum with an emission peak in the wavelength range from 500 nm to 630 nm when excited by ultraviolet to green excitation light is the phosphor having a garnet crystal structure with Ce as an activator.

7. The phosphor mixture according to claim 6, wherein the phosphor having the garnet crystal structure with the Ce as the activator, is an Al garnet phosphor containing Y and/or Tb.

8. The phosphor mixture according to claim 6, wherein the phosphor having the garnet crystal structure with the Ce as the activator, is a Si garnet phosphor containing Sc.

9. The phosphor mixture according to claim 1, wherein each of the phosphors is a particle with an average particle size (D50) of 1 to 20 μ

m.

10. The phosphor mixture according to claim 1, wherein each of the phosphors has the emission spectrum with a half value width of 50 nm or more.

11. The phosphor mixture according to claim 1, having the emission spectrum with two or more emission peaks in the wavelength range from 500 nm to 780 nm, and having a continuous spectrum without a break in the wavelength range from 500 nm to 780 nm, in the emission spectrum under an excitaion of the excitation light in the wavelength range from 430 nm to 500 nm.

12. The phosphor mixture according to claim 1, wherein a chromaticity of the emission spectrum satisfies x>

0.2, and y>

0.2, in the emission spectrum under the excitation of the excitation light with the wavelength range from 430 nm to 500 nm.

13. A light emitting device, comprising the phosphor mixture according to claim 1, and a light emitting part emitting light with the wavelength range from 430 nm to 500 nm.

14. The light emitting device according to claim 13, wherein the light emitting part is a light emitting diode (LED).

15. The light emitting device according to claim 14, wherein the light emitting part is a light emitting diode (LED) composed of a material containing Ga.

16. The light emitting device according to claim 13, wherein a general color rendering index Ra of the light emitting device is not less than 80.

17. The light emitting device according to claim 13, wherein a special color rendering index R9 of the light emitting device is not less than 60.

18. The light emitting device according to claim 13, wherein the special color rendering index R15 of the light emitting device is not less than 80.

19. The light emitting device according to claim 13, wherein a correlated color temperature of the light emitting device is in a range from 7000K to 2500K.