Phosphor mixture and light emitting device

• US 20060091790A1
• Filed: 02/22/2005
• Published: 05/04/2006
• Est. Priority Date: 10/28/2004
• Status: Active Grant

• Current Assignee: Citizen Electronics Company Limited
• Original Assignee: Dowa Mining Company Limited
• Inventors: Gotoh, Masahiro, Nagatomi, Akira, Sakane, Kenji
• Granted Patent: US 7,514,860 B2
• Time in Patent Office: Days
• US Class Current: 313/503
• CPC Class Codes: C04B 2235/3213 Strontium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3215 Barium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3418 Silicon oxide, silicic acids, or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint glass constituents C04B2235/36
• 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 2235/442 Carbonates
• CPC Class Codes: C04B 35/581 based on aluminium nitride
• CPC Class Codes: C04B 35/584 based on silicon nitride
• CPC Class Codes: C04B 35/597 based on silicon oxynitride, e.g. SIALONS
• 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 33/504 Elements with two or more wavelength conversion materials
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

To provide a light emitting device having a phosphor mixture and a light emitting part, the phosphor mixture including a red phosphor and more than one kind of phosphor having an emission spectrum with a peak in a wavelength range from 500 nm to 630 nm, and emitting light having a sufficient luminance and excellent in color rendering properties not only in a white light with high correlated color temperature, but also in a warm white light with low correlated color temperature. CaAlSiN₃:Eu manufactured as a red phosphor and and CaAl₂Si₄N₈:Eu manufactured as an orange phosphor, and for example, commercial YAG:Ce as a yellow-green phosphor, are prepared, and emission spectra of these phosphors are measured when excited by excitation light in the wavelength range from 430 nm to 500 nm. Further, the emission spectrum of the light used as an excitation light are measured, by simulation using their emission spectra, a mixing ratio of each phosphor, by which the correlated color temperature of the phosphor mixture becomes a target color temperature, is obtained. And based on the result of the simulation, each phosphor is measured nad mixed, thus obtaining the phosphor mixture.

Claims

1. A phosphor mixture, comprising:

a red phosphor expressed by a composition formula MmAaBbOoNn;

Z (wherein 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, element Z is the element acting as an activator in the phosphor, expressed by m=a=b=1, o<

0.5, n=3-2/3o.), and more than one kind of phosphor having an emission spectrum with a peak in the wavelength range from 500 nm to 630 nm.

2. The phosphor mixture according to claim 1, wherein one kind of the phosphor having the emission spectrum with a peak in the wavelength range from 500 nm to 630 nm is expressed by the composition formula MmAaBbOoNn:

Z (wherein element M is more than one kind of element having bivalent valency, element A is the 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, element Z is the element acting as an activator in the phosphor, expressed by n=2/3m+a+4/3b-2/3o, m>

0, a≧

0, b>

0, o≧

0).

3. The phosphor mixture according to claim 1, wherein one kind of the phosphor having the emission spectrum with a peak in the wavelength range from 500 nm to 630 nm is expressed by the composition formula MmAaBbOoNn:

Z (wherein 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, element Z is the element acting as an activator in the phosphor, expressed by m=1.0, a=2.0, 3.0≦

b≦

6.0, o<

1.0, n=8/3+4/3b-2/3o).

4. The phosphor mixture according to claim 1, wherein the element M is more than one kind of element selected from a 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 transition metal elements.

5. The phosphor mixture according to claim 1, wherein the element Z is Eu.

6. The phosphor mixture according to claim 1, wherein each of the phosphors has an emission spectrum of 50 nm or more in half-value width.

7. The phosphor mixture according to claim 1 having a continuous emission spectrum which has a correlated color temperature of 7000K to 2000K and has not a break in the wavelength range from 500 nm to 780 nm, when excited by excitation light having an emission spectrum in the wavelength range from 430 nm to 500 nm.

8. The phosphor mixture according to claim 1, having a continuous emission spectrum which has a correlated color temperature from 4500K to 2000K and has two or more emission peaks in the wavelength range from 500 nm to 780 nm, when excited by an excitation light having an emission spectrum in the wavelength range from 430 nm to 500 nm.

9. The phosphor mixture according to claim 1, having the emission spectrum of which the chromaticity satisfies x>

0.2, y>

0.2 when excited by the excitation light having an emission spectrum in the wavelength range from 430 nm to 500 nm.

10. The phosphor mixture according to claim 1, wherein each phosphor comprises particles having an average particle diameter of 0.1 to 20 μ

m.

11. A light emitting device having the phosphor mixture according claim 1, and a light emitting part having an emission spectrum with a peak in the wavelength range from 430 nm to 500 nm.

12. The light emitting device according to claim 11, wherein general color rendering index Ra of the light emitting device is set at not less than 80.

13. The light emitting device according to claim 11, emitting the light of which special color rendering index R9 is set at not less than 60.

14. The light emitting device according to claim 11, emitting the light of which special color rendering index R15 is set at not less than 80.

15. The light emitting device according to claim 11, emitting the light which has a correlated color temperature from 7000K to 2500K.

16. The light emitting device according to claim 11, emitting the light which has a correlated color temperature from 4500K to 2500K.

17. The light emitting device according to claim 11, having the light of which the chromaticity satisfies x>

0.3, y>

0.3.

18. The light emitting device according to claim 11, wherein the light emitting part is an light emitting diode (LED).

19. The light emitting device according to claim 18, wherein the light emitting part is the light emitting diode (LED) formed of a material containing Ga.