White light emitting device

1. A backlight of a liquid crystal display device having a white light emitting device,

wherein the white light emitting device comprises:

a light emitting diode having an emission peak in a range of 420 to 460 nm; and

a mixture of a first phosphor having an emission peak in a range of 560 to 590 nm and a second phosphor having an emission peak in a range of 510 to 550 nm disposed above the light emitting diode,

the second phosphor comprising at least one phosphor selected from the group consisting of phosphors having compositions expressed by the following formulae:

—(Sr 1−x−y−z ,Ca x ,Ba y ,Mg z ) 2 SiO 4 :EU w 2+ where 0<x<1, 0.5<y<1, 0<z<1, 0.03<w<0.2 and 0<x+y+z+w<1;

Y 3 (Al 1−x ,Ga x ) 5 O 12 : Ce, where 0<x≦1; and

Eu-activated β-sialon; and

the white light emitting device emits white light in a region of x=0.27 to 0.33, y=0.25 to 0.35 in the 1931 CIE chromaticity coordinates by combination of the light emitting diode and the mixture of the first phosphor and the second phosphor.

2. The backlight of a liquid crystal display device according to claim 1 , the white light emitting device further comprising an encapsulant, for encapsulating the light emitting diode, wherein the mixture of the first phosphor and the second phosphor is dispersed in the encapsulant.

3. The backlight of a liquid crystal display device according to claim 1 , wherein the first phosphor comprises a silicate phosphor having a composition expressed by a following formula:

(3−x−y)SrO.x(Ba,Ca)O.(1−a−b−c−d)SiO 2 .aP 2 O 5 bAl 2 O 3 .cB 2 O 3 .dGeO 2 :yEu 2+ ,

where 0≦x<2.4, 0.005<y<0.5 and 0≦a, b, c, d<0.5.

4. The backlight of a liquid crystal display device according to claim 1 , wherein the first phosphor comprises a phosphor having a composition expressed by a following formula:

Zn 1−x ,Se y S 1−y :Cu x , where 0<x<0.2 and 0.005<y<1.

5. The backlight of a liquid crystal display device according to claim 1 , wherein the first phosphor comprises a Ca-α sialon phosphor having a composition expressed by a following formula:

Ca x ; Si 12−(z+w) Al z+w O w N 16−w :Eu y 2+ , where 0.5<x<0.9, 0.01<y<0.15, 0<z<4, 0<w<4 and 0<z+w<4.

6. The backlight of a liquid crystal display device according to claim 1 , wherein the second phosphor further comprises a phosphor having a composition expressed by a following formula:

(Sr 1−x−y ,Ca x )Ga 2 (Sz,Se 1−z ) 4 :Eu y 2+ , where 0≦x<1,0<y<0.2, 0<x+y≦1 and 0<z≦1.

7. The backlight of a liquid crystal display device according to claim 1 , wherein the second phosphor comprises a phosphor selected from the group consisting of phosphors having compositions expressed by following formulae:

SrSi 2 O 2 N 2 :Eu, Ca 3 Sc 2 Si 3 O 12 :Ce, CaSc 2 O 4 :Eu and combinations thereof.

8. A white light emitting device comprising:

a blue light emitting diode; and

a mixture of orange phosphor and green phosphor disposed above the blue light emitting diode;

wherein the orange phosphor comprises at least two phosphors selected from the group consisting of phosphors having compositions expressed by following formulae:

(3−x−y)SrO.x(Ba,Ca)O.(1−a−b−c−d)SiO 2 .aP 2 O 5 bAl 2 O 3 .cB 2 O 3 .dGeO 2 :yEu 2+ , where 0≦x<2.4, 0.005<y<0.5 and 0≦a, b, c, d<0.5;

Zn 1−x Se y S 1−y :Cu x , where 0<x<0.2 and 0.005<y<1; and

Ca x Si 12−(z+w) Al z+w O w N 16−w :Eu y 2+ , where 0.5<x<0.9, 0.01<y<0.15, 0<z<4, 0<w<4 and 0<z+w<4.

9. A white light emitting device comprising:

a blue light emitting diode; and

a mixture of orange phosphor and green phosphor disposed above the blue light emitting diode;

wherein the green phosphor comprises a phosphor having a composition expressed by a following formula:

—(Sr 1−x−y−z ,Ca x ,Mg z ) 2 SiO 4 :Eu w 2+ where 0<x<1, 0.5<y<1, 0<z<1, 0.03<w<0.2 and 0<x+y+z+w<1.

10. A white light emitting device comprising:

a blue light emitting diode; and

a mixture of orange phosphor and green phosphor disposed above the blue light emitting diode;

wherein the green phosphor comprises at least two phosphors selected from the group consisting of phosphors having compositions expressed by following formulae:

(Sr 1−x−y ,Ca x )Ga 2 (S z ,Se 1−z ) 4 :Eu y 2+ , where 0≦x<1, 0<y<0.2, 0<x+y≦1 and 0<z≦1;

(Sr 1−x−y−z ,Ca x ,Ba y ,Mg z ) 2 SiO 4 :Eu w 2+ , where 0<x<1, 0.5<y<1, 0<z<1, 0.03<w<0.2 and 0<x+y+z+w<1;

Eu-activated β-sialon;

Y 3 (Al 1−x ,Ga x ) 5 O 12 :Ce, where 0<x≦1; SrSi 2 O 2 N 2 :Eu;

CaSc 2 Si 3 O 12 :Ce; and

CaSc 2 O 4 :Eu.

11. A white light emitting device comprising:

a blue light emitting diode; and

a mixture of orange phosphor and green phosphor disposed above the blue light emitting diode; wherein the orange phosphor comprises Zn(Se 0.1 ,S 0.9 ) :Cu and the green phosphor comprises Eu-activated β-sialon.

12. A white light emitting device comprising:

a blue light emitting diode; and

a mixture of orange phosphor and green phosphor disposed above the blue light emitting diode;

wherein the orange phosphor comprises Sr 3 SiO 5 :Eu and the green phosphor comprises SrGa 2 S 4 :Eu.

13. A white light emitting device comprising:

a blue light emitting diode; and

a mixture of orange phosphor and green phosphor disposed above the blue light emitting diode;

wherein the orange phosphor comprises Zn(Se 0.1 S 0.9 ) :Cu and the green phosphor comprises CaGa 2 (S,Se) 4 :Eu.

14. A display device comprising:

a display panel; and

a backlight unit which emits light to the display panel, the backlight unit comprising a while light emitting device,

wherein the white light emitting device comprises:

a light emitting diode having an emission peak in a range of 420 to 460 nm; and

a mixture of a first phosphor having an emission peak in a range of 560 to 590 nm and a second phosphor having an emission peak in a range of 510 to 550 nm disposed above the light emitting diode,

the second phosphor comprising at least one phosphor selected from the group consisting of phosphors having compositions expressed by the following formulae:

(Sr 1−x−y−z Ca x ,Ba y ,Mg z ) 2 SiO 4 :Eu w 2+ , where 0<x<1, 0.5<y<1, 0<z<1, 0.03<w<0.2 and 0<x+y+z+w<1;

Y 3 (Al 1−x ,Ga x ) 5 O 12 :Ce, where 0<x≦1; and

Eu-activated β-sialon; and

the white light emitting device emits white light in a region of x=0.27 to 0.33, y=0.25 to 0.35 in the 1931 CIE chromaticity coordinates by combination of the light emitting diode and the mixture of the first phosphor and the second phosphor.

15. The display device of claim 14 further comprising a driving circuit which drives the backlight unit.

16. The display device of claim 14 , wherein the display panel is a liquid crystal panel.

17. A television comprising the display device of claim 14 .

18. The television of claim 17 further comprising a driving circuit which drives the backlight unit.

19. The television of claim 17 , wherein the display panel is a liquid crystal panel.