Light emitting device and fabricating method thereof

• US 20060226759A1
• Filed: 05/26/2006
• Published: 10/12/2006
• Est. Priority Date: 05/30/2005
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Masuda, Masatsugu, Katoh, Masaaki, Inoguchi, Tsukasa
• Granted Patent: US 7,737,621 B2
• Time in Patent Office: Days
• US Class Current: 313/486
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/77214 Aluminosilicates
• CPC Class Codes: C09K 11/7728 containing europium
• CPC Class Codes: C09K 11/7734 Aluminates
• CPC Class Codes: C09K 11/77342 Silicates
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: C09K 11/7739 with halogens
• CPC Class Codes: H01J 1/63 characterised by the luminescent material
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• 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 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• 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 2933/0041 relating to wavelength conversion elements
• 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 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material

Abstract

A light-emitting device includes a light-emitting element for emitting primary light, and a wavelength conversion unit for absorbing part of the primary light and emitting secondary light having a wavelength longer than that of the primary light, wherein the wavelength conversion unit includes plural kinds of phosphors having light absorption characteristics different from each other, and then at least one kind of phosphor among the plural kinds of phosphors has an absorption characteristic that can absorb the secondary light emitted from at least another kind of phosphor among the plural kinds of phosphors.

Claims

1. A light-emitting device, comprising:

a light-emitting element for emitting primary light; and

a wavelength conversion unit for absorbing part of the primary light and emitting secondary light having a wavelength longer than that of the primary light;

wherein

said wavelength conversion unit includes plural kinds of phosphors different in light absorption characteristic from each other, and

at least one kind of phosphor among said plural kinds of phosphors has an absorption characteristic that can absorb the secondary light emitted by at least another kind of phosphor among said plural kinds of phosphors.

2. The light-emitting device according to claim 1, wherein said plural kinds of phosphors are arranged from the side closer to said light-emitting element in decreasing order of the wavelength of the secondary light emitted therefrom.

3. The light-emitting device according to claim 1, wherein a peak wavelength of the primary light emitted by said light-emitting element falls within the range from 400 nm to 500 nm.

4. The light-emitting device according to claim 1, wherein said wavelength conversion unit includes a combination of a phosphor for emitting blue light, a phosphor for emitting green light and a phosphor for emitting red light, or a combination of a phosphor for emitting green light and a phosphor for emitting red light.

5. The light-emitting device according to claim 4, wherein

said phosphor for emitting blue light includes at least one kind selected from

a divalent europium-activated halophosphate phosphor represented by (M1,Eu)₁₀(PO₄)₆.Cl₂,

a divalent europium-activated aluminate phosphor represented by a(M2,Eu)O.bAl₂O₃, and

a divalent europium-manganese co-activated aluminate phosphor represented by a(M2,Eu_c,Mn_d)O.bAl₂O₃,

where M1 represents at least one kind of element selected from Mg, Ca, Sr and Ba;

M2 represents at least one kind of element selected from Mg, Ca, Sr, Ba and Zn; and

a, b, c and d represent numbers satisfying a>

0, b>

0, 0.1≦

a/b≦

1.0, and 0.001≦

d/c≦

0.2.

6. The light-emitting device according to claim 4, wherein

said phosphor for emitting green light includes at least one kind selected from

a divalent europium-manganese co-activated aluminate phosphor represented by a(M2,Eu_e,Mn_f)O.bAl₂O₃,

a divalent europium-activated silicate phosphor represented by 2(M1₁₋

g,Eu_g)O.SiO₂, and

a trivalent cerium-activated silicate phosphor represented by MI₃(MII<sub>1−

h</sub>,Ce_h)₂(SiO₄)₃,

where M2 represents at least one kind of element selected from Mg, Ca, Sr, Ba and Zn;

a, b, e, and f represent numbers satisfying a>

0, b>

0, 0.1≦

a/b≦

1.0, and 0.3≦

f/e≦

5.0;

Ml represents at least one kind of element selected from Mg, Ca, Sr and Ba;

g represents a number satisfying 0.005≦

g≦

0.10;

MI represents at least one kind of element selected from Mg, Ca, Sr and Ba;

MII represents at least one kind of element selected from Al, Ga, In, Sc, Y, La, Gd and Lu; and

h represents a number satisfying 0.005≦

h≦

0.5.

7. The light-emitting device according to claim 4, wherein said phosphor for emitting red light includes a divalent europium-activated nitride phosphor represented by (MIII₁₋

j,Eu_j)MIVSiN₃, where MIII represents at least one kind of element selected from Mg, Ca, Sr and Ba, MIV represents at least one kind of element selected from Al, Ga, In, Sc, Y, La, Gd and Lu, and j represents a number satisfying 0.001≦

j≦

0.05.

8. The light-emitting device according to claim 4, wherein said light-emitting element is covered with a plurality of resin layers, each of said resin layers including one of said phosphor for red light, said phosphor for green light and said phosphor for blue light, and then the phosphor contained in the resin layer closer to said light-emitting element emits the secondary light having a longer peak wavelength as compared to the phosphor contained in the resin layer farther from said light-emitting element.

9. The light-emitting device according to claim 8, wherein said light-emitting element is placed in a cup of a package, and said cup has an inner wall provided with a terrace to cause each of the phosphor layers containing said plural kinds of phosphors to have a uniform thickness.

10. The light-emitting device according to claim 9, wherein the inner wall of said cup is formed to be inclined steeper in an upper part than in an lower part with a boundary formed by the terrace, in order to reduce shade of the terrace which is caused in the upper phosphor layer by light emitted from the lower phosphor layer.

11. The light-emitting device according to claim 2, wherein said plural kinds of phosphors have median sizes different from each other.

12. The light-emitting device according to claim 1, wherein an optical film for transmitting said secondary light and reflecting only said primary light selectively depending on their wavelengths is provided between an outermost surface of said wavelength conversion unit and an exterior space.

13. A light-emitting device, comprising:

a light-emitting element for emitting primary light; and

a wavelength conversion unit for absorbing at least part of said primary light and emitting secondary light having a wavelength longer than that of the primary light;

wherein

said wavelength conversion unit includes at least a phosphor for emitting green light and a phosphor for emitting red light, and

said phosphor for green light includes a divalent europium-manganese co-activated aluminate phosphor represented by a(M2,Eu_e,Mn_f)O.bAl₂O₃, where M2 represents at least one kind of element selected from Mg, Ca, Sr, Ba and Zn; and

a, b, e and f represent numbers satisfying a>

0, b>

0, 0.1≦

a/b≦

1.0 and 0.3≦

f/e≦

5.0.

14. The light-emitting device according to claim 13, wherein said phosphor for emitting red light includes a divalent europium-activated nitride phosphor represented by (M3₁₋

gEu_g)M4SiN₃, where M3 represents at least one kind of element selected from Mg, Ca, Sr and Ba;

M4 represents at least one kind of element selected from Al, Ga, In, Sc, Y, La, Gd and Lu; and

g represents a number satisfying 0.001≦

g≦

0.05.

15. The light-emitting device according to claim 13, wherein

said wavelength conversion unit further includes a phosphor for emitting blue light, said phosphor for blue light including at least one kind selected from

a divalent europium-activated halophosphate phosphor represented by. (M1,Eu)₁₀(PO₄)₆.Cl₂,

a divalent europium-activated aluminate phosphor represented by a(M2,Eu)O.bAl₂O₃, and

a divalent europium-manganese co-activated aluminate phosphor represented by a(M2,Eu_c,Mn_d)O.bAl₂O₃,

where M1 represents at least one kind of element selected from Mg, Ca, Sr and Ba;

M2 represents at least one kind of element selected from Mg, Ca, Sr, Ba and Zn; and

a, b, c and d represent numbers satisfying a>

0, b>

0, 0.1≦

a/b≦

1.0, and 0.001≦

d/c≦

0.2.

16. The light-emitting device according to claim 13, wherein said light-emitting element is formed of a gallium nitride-based semiconductor, and said primary light has a peak wavelength in the range from 380 nm to 450 nm.

17. The light-emitting device according to claim 15, wherein wavelength components of said primary light emitted from said light-emitting element and wavelength components of said secondary light emitted from each of said phosphors for red light, green light and blue light are adjusted such that light emitted from said light-emitting device has chromaticity that is regarded as blackbody radiation of a prescribed color temperature.

18. The light-emitting device according to claim 15, wherein said light-emitting element is covered with a plurality of resin layers, each of said resin layers including one of said phosphor for red light, said phosphor for green light and said phosphor for blue light, and then the phosphor included in the resin layer closer to said light-emitting element emits the secondary light having a longer peak wavelength as compared to the phosphor included in the resin layer farther from said light-emitting element.

19. The light-emitting device according to claim 18, wherein said light-emitting element is placed in a cup of a package, and said cup has an inner wall provided with a terrace to cause each of the phosphor layers containing said plural kinds of phosphors to have a uniform thickness.

20. The light-emitting device according to claim 19, wherein the inner wall of said cup is formed to be inclined steeper in an upper part than in an lower part with a boundary formed by the terrace, in order to reduce shade of the terrace which is caused in the upper phosphor layer by light emitted from the lower phosphor layer.

21. The light-emitting device according to claim 18, wherein said plural kinds of phosphors have median sizes different from each other.

22. The light-emitting device according to claim 13, wherein an optical film for transmitting said secondary light and reflecting only said primary light selectively depending on their wavelengths is provided between an outermost surface of said wavelength conversion unit and an exterior space.

23. A fabrication method of a light-emitting device, comprising the steps of:

mounting a light-emitting element on a bottom surrounded by a reflective surface of an inner wall in a package;

introducing and setting a first liquid resin kneaded with a first kind of phosphor to cover said light-emitting element mounted in said package; and

introducing and setting a second liquid resin kneaded with a second kind of phosphor on said first liquid resin thus set and on said reflective surface,

wherein the second kind of phosphor has a secondary light wavelength shorter than that of said first kind of phosphor.

24. A fabrication method of a light-emitting device, comprising the steps of:

mounting a light-emitting element on a bottom surrounded by a reflective surface of an inner wall in a package;

introducing a liquid resin kneaded with plural kinds of phosphors having different median values of particle sizes, to cover said light-emitting element mounted in said package; and

leaving said introduced liquid resin at rest for a prescribed time period to cause the phosphor particles to settle such that a particular kind of the phosphor having a greater median value of the particle size has a greater concentration near said light-emitting element.