Light emitting apparatus with open loop control

• US 20090015137A1
• Filed: 02/08/2008
• Published: 01/15/2009
• Est. Priority Date: 07/13/2007
• Status: Active Grant

• Current Assignee: Lite-On Technology Corporation
• Original Assignee: Lite-On Technology Corporation
• Inventors: Su, Hung-Yuan, Liu, Ru-Shi
• Granted Patent: US 7,838,896 B2
• Time in Patent Office: Days
• US Class Current: 313/503
• CPC Class Codes: H01J 1/63 characterised by the luminescent material
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials

Abstract

A light emitting apparatus includes a blue light emitting diode (LED), a first and second phosphor layers. The second phosphor layer is between the blue LED and the first phosphor layer. When a blue beam of a shorter wavelength excites the phosphor layers, the excitation efficiency of the first phosphor layer is greater than that of the second phosphor layer. When a blue beam of a longer wavelength excites the phosphor layers, the excitation efficiency of the first phosphor layer is less than that of the second phosphor layer. Moreover, the wavelength of the peak intensity of the light beam from the first phosphor layer is shorter than that of the second phosphor layer. And, the dividing value between the shorter wavelength and the longer wavelength is within the range from a first wavelength to a second wavelength.

Claims

1. A light emitting apparatus with open loop control, comprising:

a blue light emitting diode (LED);

a first phosphor layer disposed above the blue LED, wherein the first phosphor layer has a first phosphor material that is excited by a blue beam from the blue LED; and

a second phosphor layer disposed between the blue LED and the first phosphor layer, wherein the second phosphor layer has a second phosphor material that is excited by the blue beam from the blue LED;

wherein when a blue beam of a shorter wavelength excites the first and second phosphor layers, the excitation efficiency of the first phosphor layer is greater than that of the second phosphor layer;

when a blue beam of a longer wavelength excites the first and second phosphor layers, the excitation efficiency of the first phosphor layer is less than that of the second phosphor layer, the wavelength of the peak intensity of the light beam from the first phosphor layer is shorter than that of the second phosphor layer, and the dividing value between the short wavelength and the long wavelength is within the range from a first wavelength to a second wavelength.

2. The light emitting apparatus according to claim 1, wherein the second phosphor layer covers the blue LED directly, and the first phosphor layer covers the second phosphor layer directly.

3. The light emitting apparatus according to claim 1, further comprising:

a transparent sealed body for receiving the blue LED, wherein the second phosphor layer is disposed over the transparent sealed body, and the first phosphor layer is disposed over the second phosphor layer.

4. The light emitting apparatus according to claim 1, wherein the second phosphor layer is formed over the blue LED by coating and the first phosphor layer is formed over the second phosphor layer by coating.

5. The light emitting apparatus according to claim 1, wherein the first wavelength is approximately 440 nm, and the second wavelength is approximately 480 nm.

6. The light emitting apparatus according to claim 1, wherein the weight ratio of the first phosphor material to the second phosphor material is determined according to the emission intensities of the first and second phosphor materials.

7. The light emitting apparatus according to claim 1, wherein when the blue LED comprises a nitride compound semiconductor, the dominant wavelength of the blue beam from the blue LED is within the range from 430 to 490 nm.

8. The light emitting apparatus according to claim 1, wherein the first phosphor material is selected from (Ba_xSr_yCa_z)₂SiO₄:

Eu phosphor, wherein x+y+z=1;

or (Ba_xSr_yCa_z)₃SiO₅;

Eu phosphor, wherein x+y+z=1;

or (Ba_xSr_yCa_z)₃SiO₅;

Ce, Li phosphor, wherein x+y+z=1;

or M_xGa₂S₄;

Eu phosphor, wherein 1≦

x<

1.2, and M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba) and magnesium (Mg) or the above-mentioned metal elements;

or M_1-xSi₂N_2-yO_2-z;

A phosphor, wherein 0<

x≦

1, 0≦

y≦

1, 0≦

z≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba) and magnesium (Mg) or the above-mentioned metal elements, and A is selected from a group consisting of europium (Eu), cerium (Ce), manganese (Mn) and dysprosium (Dy) or the above-mentioned metal elements;

or Ca₃M₂Si₃O₁₂;

Ce phosphor, M is selected from a group consisting of strontium (Sr), scandium (Sc), magnesium (Mg) and barium (Ba) or the above-mentioned metal elements;

or CaSc₂O₄;

Ce phosphor;

or Ca_8-x (Mg, Mn) (SiO₄)₄Cl₂;

Eu phosphor, wherein 0<

x≦

1;

or M_xSi_12-y-zAl_y+zO_zN_16-z;

Ce phosphor, wherein 0<

x≦

1, 0≦

y≦

1, 0≦

z≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba), magnesium (Mg), lithium (Li) and yttrium (Y) or the above-mentioned metal elements;

or M_xSi_12-y-zAl_y+zO_zN_16-z;

Yb phosphor, wherein 0<

x≦

1, 0≦

y≦

1, 0≦

z≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba), magnesium (Mg), lithium (Li) and yttrium (Y) or the above-mentioned metal elements;

or M_xSi_6-zAl_zO_zN_8-z;

Eu phosphor, wherein 0<

z≦

4.2, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba) and magnesium (Mg) or the above-mentioned metal elements.

9. The light emitting apparatus according to claim 8, wherein the mean value of the particle diameters of the first phosphor material is less than 20 μ

m.

10. The light emitting apparatus according to claim 8, wherein

when the number of the particles of the first phosphor material is about 10% of the total number of the particles of the first and second phosphor materials, the particle diameter of the first phosphor material is equal to or less than 5 μ

m;

when the number of the particles of the first phosphor material is about 50% of the total number of the particles of the first and second phosphor materials, the particle diameter of the first phosphor material is equal to or less than 15 μ

m;

when the number of the particles of the first phosphor material is about 90% of the total number of the particles of the first and second phosphor materials, the particle diameter of the first phosphor material is equal to or less than 25 μ

m.

11. The light emitting apparatus according to claim 1, wherein the second phosphor material is selected from a garnet phosphor activated by cerium (Ce) and composed of at least one element of yttrium (Y), terbium (Tb), lanthanum (La), gadolinium (Gd) and samarium (Sm) and at least one element of aluminum (Al), gallium (Ga), indium (In) and iron (Fe);

or M_xS;

Eu phosphor, wherein 1≦

x<

1.2, and M is selected from a group consisting of calcium (Ca), strontium (Sr) and barium (Ba) or the above-mentioned metal elements;

or Ca_xAl_ySi_zN₃;

Ce phosphor, wherein 0<

x≦

1, 0<

y≦

1, 0<

z≦

1;

or (Ca_xAl_1-x) Si_yN_2-zO_z;

Ce phosphor, wherein 0<

x≦

1, 0<

y≦

1, 0<

z≦

1;

or M_1-xSi₂N_2-yO_2-z;

Yb phosphor, wherein 0<

x≦

1, 0<

y≦

1, 0<

z≦

1, and M is selected from a group consisting of calcium (Ca), strontium (Sr) and barium (Ba) or the above-mentioned metal elements;

or M_2-xSi₅N_8-y;

N phosphor, wherein 0<

x≦

1, 0≦

y≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr) and barium (Ba) or the above-mentioned metal elements, and N is selected from a group consisting of europium (Eu), cerium (Ce), manganese (Mn) and dysprosium (Dy) or the above-mentioned metal elements;

or A_2-x(MF₆);

Mn phosphor, wherein 0<

x≦

1, A is selected from a group consisting of potassium (K), rubidium (Rb) and cesium (Cs) or the above-mentioned metal elements, and M is selected from a group consisting of silicon (Si), germanium (Ge) and titanium (Ti) or the above-mentioned metal elements;

or MAlSiN₃;

Eu phosphor, M is selected from a group consisting of calcium (Ca), strontium (Sr) and barium (Ba) or the above-mentioned metal elements;

or M_xS_12-y-zAl_y+zO_zN_16-z;

Eu phosphor, wherein 0<

x≦

1, 0≦

y≦

1, 0≦

z≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba), magnesium (Mg), lithium (Li) and yttrium (Y) or the above-mentioned metal elements.

12. The light emitting apparatus according to claim 11, wherein the mean value of the particle diameters of the second phosphor material is less than 20 μ

m.

13. The light emitting apparatus according to claim 11, wherein

when the number of the particles of the second phosphor material is about 10% of the total number of the particles of the first and second phosphor materials, the particle diameter of the second phosphor material is equal to or less than 5 μ

m;

when the number of the particles of the second phosphor material is about 50% of the total number of the particles of the first and second phosphor materials, the particle diameter of the second phosphor material is equal to or less than 15 μ

m;

when the number of the particles of the second phosphor material is about 90% of the total number of the particles of the first and second phosphor materials, the particle diameter of the second phosphor material is equal to or less than 25 μ

m.

14. The light emitting apparatus according to claim 1, wherein the first and second phosphor materials are selected from a group consisting of (Ba_xSr_yCa_z)₂SiO₄:

Eu phosphor, (Ba_xSr_yCa_z)₃SiO₅;

Eu phosphor, and (Ba_xSr_yCa_z)₃SiO₅;

Ce, Li phosphor, x+y+z=1.

15. A light emitting apparatus with open loop control, comprising:

a blue LED; and

a phosphor layer covering the blue LED, and having a first phosphor material and a second phosphor material, wherein the first and second phosphor materials are excited by a blue beam from the blue LED;

wherein when a blue beam of a shorter wavelength excites the first and second phosphor materials, the excitation efficiency of the first phosphor material is greater than that of the second phosphor material;

when a blue beam of a longer wavelength excites the first and second phosphor materials, the excitation efficiency of the first phosphor material is less than that of the second phosphor material, the wavelength of the peak intensity of the light beam from the first phosphor material is shorter than that of the second phosphor material, and the dividing value between the shorter wavelength and the longer wavelength is within the range from a first wavelength to a second wavelength.

16. The light emitting apparatus according to claim 15, further comprising:

a transparent sealed body for receiving the blue LED, wherein the phosphor layer is disposed over the transparent sealed body.

17. The light emitting apparatus according to claim 15, wherein the first wavelength is approximately 440 nm, and the second wavelength is approximately 480 nm.

18. The light emitting apparatus according to claim 15, wherein the weight ratio of the first phosphor material to the second phosphor material is determined according to the emission intensities of the first and second phosphor materials.

19. The light emitting apparatus according to claim 15, wherein when the blue LED comprises a nitride compound semiconductor, the dominant wavelength of blue beam from the blue LED is within the range from 430 to 490 nm.

20. The light emitting apparatus according to claim 15, wherein at least one of the first and second phosphor materials has a mean value of the particle diameters less than 20 μ

m.

21. The light emitting apparatus according to claim 15, wherein the first phosphor material is selected from (Ba_xSr_yCa_z)₂SiO₄:

Eu phosphor, wherein x++y+z=1;

or (Ba_xSr_yCa_z)₃SiO₅;

Eu phosphor, wherein x+y+z=1;

or (Ba_xSr_yCa_z)₃SiO₅;

Ce, Li phosphor, wherein x+y+z=1;

or M_xGa₂S₄;

Eu phosphor, wherein 1≦

x<

1.2, and M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba) and magnesium (Mg) or the above-mentioned metal elements;

or M_1-xSi₂N_2-yO_2-z;

A phosphor, wherein 0<

x≦

1, 0≦

y≦

1, 0≦

z≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba) and magnesium (Mg) or the above-mentioned metal elements, and A is selected from a group consisting of europium (Eu), cerium (Ce), manganese (Mn) and dysprosium (Dy) or the above-mentioned metal elements;

or Ca₃M₂Si₃O₁₂;

Ce phosphor, M is selected from a group consisting of strontium (Sr), scandium (Sc), magnesium (Mg) and barium (Ba) or the above-mentioned metal elements;

or CaSc₂O₄;

Ce phosphor;

or Ca_8-x(Mg, Mn) (SiO₄)₄Cl₂;

Eu phosphor, wherein 0<

x≦

1;

or M_xSi_12-y-zAl_y+zO_zN_16-z;

Ce phosphor, wherein 0<

x≦

1, 0≦

y≦

1, 0≦

z≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba), magnesium (Mg), lithium (Li) and yttrium (Y) or the above-mentioned metal elements;

or M_xSi_12-y-zAl_y+zO_zN_16-z;

Yb phosphor, wherein 0<

x≦

1, 0≦

y≦

1, 0≦

z≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba), magnesium (Mg), lithium (Li) and yttrium (Y) or the above-mentioned metal elements;

or M_xSi_6-zAl_zO_zN_8-z;

Eu phosphor, wherein 0<

z≦

4.2, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba) and magnesium (Mg) or the above-mentioned metal elements.

22. The light emitting apparatus according to claim 21, wherein

when the number of the particles of the first phosphor material is about 10% of the total number of the particles of the first and second phosphor materials, the particle diameter of the first phosphor material is equal to or less than 5 μ

m;

when the number of the particles of the first phosphor material is about 50% of the total number of the particles of the first and second phosphor materials, the particle diameter of the first phosphor material is equal to or less than 15 μ

m;

when the number of the particles of the first phosphor material is about 90% of the total number of the particles of the first and second phosphor materials, the particle diameter of the first phosphor material is equal to or less than 25 μ

m.

23. The light emitting apparatus according to claim 15, wherein the second phosphor material is selected from a garnet phosphor activated by cerium (Ce) and composed of at least one element of yttrium (Y), terbium (Tb), lanthanum (La), gadolinium (Gd) and samarium (Sm) and at least one element of aluminum (Al), gallium (Ga), indium (In) and iron (Fe);

or M_xS;

Eu phosphor, wherein 1≦

x<

1.2, and M is selected from a group consisting of calcium (Ca), strontium (Sr) and barium (Ba) or the above-mentioned metal elements;

or Ca_xAl_ySi_zN₃;

Ce phosphor, wherein 0<

x≦

1, 0<

y≦

1, 0<

z≦

1;

or (Ca_xAl_1-x) Si_yN_2-zO_z;

Ce phosphor, wherein 0<

x≦

1, 0<

y≦

1, 0<

z≦

1;

or M_1-xSi₂N_2-yO_2-z;

Yb phosphor, wherein 0<

x≦

1, 0≦

y≦

1, 0≦

z≦

1, and M is selected from a group consisting of calcium (Ca), strontium (Sr) and barium (Ba) or the above-mentioned metal elements;

or M_2-xSi₅N_8-y;

N phosphor, wherein 0<

x≦

1, 0≦

y≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr) and barium (Ba) or the above-mentioned metal elements, and N is selected from a group consisting of europium (Eu), cerium (Ce), manganese (Mn) and dysprosium (Dy) or the above-mentioned metal elements;

or A_2-x(MF₆);

Mn phosphor, wherein 0<

x≦

1, A is selected from a group consisting of potassium (K), rubidium (Rb) and cesium (Cs) or the above-mentioned metal elements, and M is selected from a group consisting of silicon (Si), germanium (Ge) and titanium (Ti) or the above-mentioned metal elements;

or MAlSiN₃;

Eu phosphor, M is selected from a group consisting of calcium (Ca), strontium (Sr) and barium (Ba) or the above-mentioned metal elements;

or M_xSi_12-y-zAl_y+zO_zN_16-z;

Eu phosphor, wherein 0<

x≦

1, 0≦

y≦

1, 0≦

z≦

1, M is selected from a group consisting of calcium (Ca), strontium (Sr), barium (Ba), magnesium (Mg), lithium (Li) and yttrium (Y) or the above-mentioned metal elements.

24. The light emitting apparatus according to claim 23, wherein

when the number of the particles of the second phosphor material is about 10% of the total number of the particles of the first and second phosphor materials, the particle diameter of the second phosphor material is equal to or less than 5 μ

m;

when the number of the particles of the second phosphor material is about 50% of the total number of the particles of the first and second phosphor materials, the particle diameter of the second phosphor material is equal to or less than 15 μ

m;

when the number of the particles of the second phosphor material is about 90% of the total number of the particles of the first and second phosphor materials, the particle diameter of the second phosphor material is equal to or less than 25 μ

m.

25. The light emitting apparatus according to claim 15, wherein the first and second phosphor materials are selected from a group consisting of (Ba_xSr_yCa_z)₂SiO₄:

Eu phosphor, (Ba_xSr_yCa_z)₃SiO₅;

Eu phosphor, and (Ba_xSr_yCa_z)₃SiO₅;

Ce, Li phosphor, x+y+z=1.