Light emitting device including first and second red phosphors and a green phosphor

1. A light emitting device comprising:

a light emitting element emitting light having a wavelength of 380 nm to 470 nm;

a first red phosphor disposed on the light emitting element, the first red phosphor having a composition expressed by equation (1);

a second red phosphor disposed on the light emitting element, the second red phosphor having a composition expressed by equation (2); and

a green phosphor disposed on the light emitting element, the green phosphor having a composition expressed by equation (3),

(Ca 1−x1 Eu x1 ) a1 AlSi b1 O c1 N d1 :Eu  (1)

wherein, in the equation (1), x1, a1, b1, c1 and d1 satisfy the following relationship: 0<x1<0.03, 0.90<a1<1.1, 0.9<b1<1.1, 0.20<c1<0.45, 2.40<d1≦3.00,

(Sr 1−x2 Eu x2 ) a2 Si b2 AlO c2 N d2 :Eu  (2)

wherein, in the equation (2), x2, a2, b2, c2, and d2 satisfy the following relationship: 0<x2≦1, 0.60<a2<0.95, 2.0<b2<3.9, 0.04≦c2≦0.6, 4<d2<5.7,

(Sr 1−x Eu x ) 3−y Si 13−z Al 3+z O 2+u N 21−w :Eu  (3)

wherein, in the equation (3), x, y, z, u, and w satisfy the following relationship: 0<x≦1, −0.1≦y≦0.15, −1≦z≦1, −1<u−w≦1.5.

2. The device according to claim 1 , wherein the light emitting element emits light having a wavelength of 440 nm to 470 nm.

3. The device according to claim 1 , wherein x2, a2, b2, c2, and d2 satisfy a relationship of 0.01<x2≦0.10, 0.62≦a2≦0.70, 2.1≦b2≦2.5, 0.4≦c2≦0.5, 4.1≦d2≦4.5 in the equation (2).

4. The device according to claim 2 , wherein x2, a2, b2, c2, and d2 satisfy the relationship of 0.01<x2≦0.10, 0.62≦a2≦0.70, 2.1≦b2≦2.5, 0.4≦c2≦0.5, 4.1≦d2≦4.5 in the equation (2).

5. The device according to claim 1 , further comprising a blue phosphor disposed on the light emitting element.

6. The device according to claim 5 , wherein the light emitting element emits light having a wavelength of 380 nm to 420 nm.

7. A device comprising:

a board;

a light emitting element mounted on the board;

a red fluorescent layer formed on the light emitting element, the red fluorescent layer including a first red phosphor having a composition expressed by equation (1) and a second red phosphor having a composition expressed by equation (2), the first red phosphor and the second red phosphor being dispersed in a resin; and

a green fluorescent layer formed on the red fluorescent layer, the green fluorescent layer including a green phosphor dispersed in a resin, the green phosphor having a composition expressed by equation (3),

(Ca 1−x1 Eu x1 ) a1 AlSi b1 O c1 N d1 :Eu  (1)

wherein, in the equation (1), x1, a1, b1, c1 and d1 satisfy the following relationship: 0<x1<0.03, 0.90<a1<1.1, 0.90<b1<1.1, 0.20<c1<0.45, 2.40<d1≦3.00,

(Sr 1−x2 Eu x2 ) a2 Si b2 AlO c2 N d2 :Eu  (2)

wherein, in the equation (2), x2, a2, b2, c2, and d2 satisfy the following relationship: 0<x2≦1, 0.60<a2<0.95, 2.0<b2<3.9, 0.04≦c2≦0.6, 4<d2<5.7,

(Sr 1−x Eu x ) 3−y Si 13−z Al 3+z O 2+u N 21−w :Eu  (3)

wherein, in the equation (3), x, y, z, u, and w satisfy the following relationship: 0<x≦1, −0.1≦y≦0.15, −1≦z≦1, −1<u−w≦1.5.

8. The device according to claim 7 , wherein the light emitting element emits light having a wavelength of 440 nm to 470 nm.

9. The device according to claim 7 , wherein x2, a2, b2, c2, and d2 satisfy a relationship of 0.01<x2≦0.10, 0.62≦a2≦0.70, 2.1≦b2≦2.5, 0.4≦c2≦0.5, 4.1≦d2≦4.5 in the equation (2).

10. The device according to claim 8 , wherein x2, a2, b2, c2, and d2 satisfy a relationship of 0.01<x2≦0.10, 0.62≦a2≦0.70, 2.1≦b2≦2.5, 0.4≦c2≦0.5, 4.1≦d2≦4.5 in the equation (2).

11. The device according to claim 7 , further comprising a blue fluorescent layer formed on the green fluorescent layer, the blue fluorescent layer including a blue phosphor dispersed in a resin.

12. The device according to claim 11 , wherein the light emitting element emits light having a wavelength of 380 nm to 420 nm.

13. The device according to claim 7 , further comprising a transparent resin layer formed between the red fluorescent layer and the green fluorescent layer.

14. A light emitting device comprising:

a board;

a light emitting element mounted on the board;

a first red fluorescent layer formed on the light emitting element, the first red fluorescent layer including a first red phosphor dispersed in a resin, the first red phosphor having a composition expressed by equation (1);

a second red fluorescent layer formed on the first red fluorescent layer, the second red fluorescent layer including a second red phosphor dispersed in a resin, the second red phosphor having a composition expressed by equation (2); and

a green fluorescent layer formed on the second red fluorescent layer, the green fluorescent layer including a green phosphor dispersed in a resin, the green phosphor having a composition expressed by equation (3),

(Ca 1−x1 Eu x1 ) a1 AlSi b1 O c1 N d1 :Eu  (1)

wherein, in the equation (1), x1, a1, b1, c1 and d1 satisfy the following relationship: 0<x1<0.03, 0.90<a1<1.1, 0.90<b1<1.1, 0.20<c1<0.45, 2.40<d1≦3.00,

(Sr 1−x2 Eu x2 ) a2 Si b2 AlO c2 N d2 :Eu  (2)

wherein, in the equation (2), x2, a2, b2, c2, and d2 satisfy the following relationship: 0<x2≦1, 0.60<a2<0.95, 2.0<b2<3.9, 0.04≦c2≦0.6, 4<d2<5.7,

(Sr 1−x Eu x ) 3−y Si 13−z Al 3+z O 2+u N 21−w :Eu  (3)

wherein, in the equation (3), x, y, z, u, and w satisfy the following relationship: 0<x≦1, −0.1≦y≦0.15, −1≦z≦1, −1<u−w≦1.5.

15. The device according to claim 14 , wherein the light emitting element emits light having a wavelength of 440 nm to 470 nm.

16. The device according to claim 14 , wherein x2, a2, b2, c2, and d2 satisfy a relationship of 0.01<x2≦0.10, 0.62≦a2≦0.70, 2.1≦b2≦2.5, 0.4≦c3≦0.5, 4.1≦d2≦4.5 in the equation (2).

17. The device according to claim 15 , wherein x2, a2, b2, c2, and d2 satisfy a relationship of 0.01<x2≦0.10, 0.62≦a2≦0.70, 2.1≦b2≦2.5, 0.4≦c2≦0.5, 4.1≦d2≦4.5 in the equation (2).

18. The device according to claim 14 , further comprising a blue fluorescent layer formed on the green fluorescent layer, the blue fluorescent layer including a blue phosphor dispersed in a resin.

19. The device according to claim 18 , wherein the light emitting element emits light having a wavelength of 380 nm to 420 nm.

20. The device according to claim 14 , further comprising a transparent resin layer formed between the second red fluorescent layer and the green fluorescent layer.