Semiconductor light emitting device, backlight, color image display device and phosphor to be used for them
To provide a semiconductor light emitting device which is capable of accomplishing a broad color reproducibility for an entire image without losing brightness of the entire image. A light source provided on a backlight for a color image display device has a semiconductor light emitting device comprising a solid light emitting device to emit light in a blue or deep blue region or in an ultraviolet region and phosphors, in combination. The phosphors comprise a green emitting phosphor and a red emitting phosphor. The green emitting phosphor and the red emitting phosphor are ones, of which the rate of change of the emission peak intensity at 100° C. to the emission intensity at 25° C., when the wavelength of the excitation light is 400 nm or 455 nm, is at most 40%.
1. A semiconductor light emitting device, comprising:
a solid light emitting device to emit light in a blue or deep blue region or in an ultraviolet region and phosphors, in combination,
wherein the phosphors comprise a green emitting phosphor having at least one emission peak in a wavelength region of from 515 to 550 nm and a red emitting phosphor having at least one emission peak with a half-value width of at most 10 nm in a wavelength region of from 610 to 650 nm;
the red emitting phosphor has substantially no excitation spectrum in the emission wavelength region of the green emitting phosphor and comprises Mn 4+ as an activated element;
the green emitting phosphor and the red emitting phosphor have the variation rate of the emission peak intensity at 100° C. to the emission intensity at 25° C. of at most 40%, when the wavelength of the excitation light is 400 nm or 455 nm; and
wherein the red emitting phosphor comprises a crystal phase having a chemical composition represented by the following formula (1′), wherein the proportion of Mn based on the total mols of M IV′ and Mn is at least 0.1 mol % and at most 6 mol %, and the specific surface area is at most 1.3 m 2 /g:
M I′ 2 M IV′ F 6 :R (1′)
wherein
M I′ is at least one element selected from the group consisting of K and Na,
M IV′ is at least one metal element selected from the group consisting of Groups 4 and 14 of the Periodic Table comprising at least Si, and
R is an activated element comprising at least Mn, and
wherein thermally decomposed F amount per 1 g of the red emitting phosphor is at most 2 μg/min.
2. The semiconductor light emitting device according to claim 1 , wherein the green emitting phosphor comprises at least one compound selected from the group consisting of an aluminate phosphor, a sialon phosphor and an oxynitride phosphor.
3. The semiconductor light emitting device according to claim 1 , wherein the red emitting phosphor has the variation rate of the emission peak intensity at 100° C. to the emission peak intensity at 25° C. of at most 18%, when the wavelength of the excitation light is 455 nm.
4. The semiconductor light emitting device according to claim 1 , wherein the red emitting phosphor has a main emission peak with a half-value width of at most 10 nm in a wavelength region of from 610 to 650 nm.
5. The semiconductor light emitting device according to claim 1 , wherein the red emitting phosphor is a fluoride complex phosphor, and the solid light emitting device is formed on an electrically conductive substrate.
6. The semiconductor light emitting device according to claim 5 , wherein the red emitting phosphor has at least 0.01 μg/min of thermally decomposed fluorine amount per 1 g of the phosphor at 200° C.
7. The semiconductor light emitting device according to claim 6 , wherein the red emitting phosphor has a solubility of at least 0.005 g and at most 7 g in 100 g of water at 20° C.
8. The semiconductor light emitting device according to claim 1 , wherein the red emitting phosphor is a fluoride complex phosphor, and the semiconductor light emitting device comprise a layer comprising the red emitting phosphor and has at least one of the following structures (a) to (c):
(a) a layer of a material not containing the red emitting phosphor between the solid light emitting device and the layer containing the red emitting phosphor,
(b) part or whole of the surface of the light emitting device covered by a layer of a material not containing the red emitting phosphor, and
(c) the layer comprising the red emitting phosphor, covered by a layer of a material not containing the red emitting phosphor.
9. The semiconductor light emitting device according to claim 8 , wherein the red emitting phosphor has at least 0.01 μg/min of thermally decomposed fluorine amount per 1 g of the phosphor at 200° C.
10. The semiconductor light emitting device according to claim 9 , wherein the red emitting phosphor has at least 0.005 g and at most 7 g of solubility in 100 g of water at 20° C.
11. The semiconductor light emitting device according to claim 1 , wherein the red emitting phosphor comprises a crystal phase having a chemical composition represented by any one of the following formulae (1) to (8):
M I 2 [M IV 1−x R x F 6 ] (1)
M I 3 [M III 1−x R x F 6 ] (2)
M II [M IV 1−x R x F 6 ] (3)
M I 3 [M IV 1−x R x F 7 ] (4)
M I 2 [M III 1−x R x F 5 ] (5)
Zn 2 [M III 1−x R x F 7 ] (6)
M I [M III 2−2x R 2x F 7 ] (7)
Ba 0.65 Zr 0.35 F 2.70 :Mn 4+ (8)
wherein in the formulae (1) to (8), M I is at least one monovalent group selected from the group consisting of Li, Na, K, Rb, Cs and NH 4 , M II is an alkaline earth metal element, M III is at least one metal element selected from the group consisting of Groups 3 and 13 of the Periodic Table, M IV is at least one metal element selected from the group consisting of Groups 4 and 14 of the Periodic Table, R is an activated element comprising at least Mn, and x is a numerical value of 0<x<1.
12. A backlight having the semiconductor light emitting device according to claim 1 as a light source.
13. A color image display device comprising light shutters, a color filter having at least trichromatic color elements of red, green and blue corresponding to the light shutters and the backlight as defined in claim 12 , in combination, wherein the relationship between the light use efficiency Y and the NTSC ratio W representing the color reproduction range of the color image display device is represented by the following formula:
Y
≧
-
0.4
W
+
64
(
where
W
≧
85
)
X
=
∫
380
780
x
_
(
λ
)
S
(
λ
)
T
(
λ
)
ⅆ
λ
∫
380
780
y
_
(
λ
)
S
(
λ
)
ⅆ
λ
x
=
X
X
+
Y
+
Z
Y
=
∫
380
780
y
_
(
λ
)
S
(
λ
)
T
(
λ
)
ⅆ
λ
∫
380
780
y
_
(
λ
)
S
(
λ
)
ⅆ
λ
y
=
Y
X
+
Y
+
Z
Z
=
∫
380
780
z
_
(
λ
)
S
(
λ
)
T
(
λ
)
ⅆ
λ
∫
380
780
y
_
(
λ
)
S
(
λ
)
ⅆ
λ
wherein the definitions of the respective symbols are as follows:
x(λ), y(λ), z(λ): color matching functions of XYZ color system
S(λ): relative emission spectrum of the backlight
T(λ): transmittance of the color filter.
14. The color image display device according to claim 13 , wherein the green pixel of the color filter comprises a zinc phthalocyanine bromide pigment.
15. The color image display device according to claim 13 , wherein each pixel of the color filter has a film thickness of at least 0.5 μm and at most 3.5 μm.
16. The color image display device according to claim 14 , wherein each pixel of the color filter has a film thickness of at least 0.5 μm and at most 3.5 μm.
17. The semiconductor light emitting device according to claim 1 , wherein the particle size distribution of the red emitting phosphor has one peak value.
18. The semiconductor light emitting device according to claim 1 , wherein M I′ is K.
19. The semiconductor light emitting device according to claim 1 , wherein M IV′ is Si.
20. The semiconductor light emitting device according to claim 1 , wherein the specific surface area is at most 1.1 m 2 /g.
21. A semiconductor light emitting device comprising a phosphor,
wherein the phosphor comprises a crystal phase having a chemical composition represented by the formula (1′):
M I′ 2 M IV′ F 6 :R (1′)
wherein
M I′ is at least one element selected from the group consisting of K and Na,
M IV′ is at least one metal element selected from the group consisting of Groups 4 and 14 of the Periodic Table comprising at least Si, and
R is an activated element comprising at least Mn, and
wherein the proportion of Mn based on the total mols of M IV′ and Mn is at least 0.1 mol % and at most 6 mol % and the specific surface area is at most 1.3 m 2 /g.
22. The semiconductor light emitting device according to claim 1 , wherein the red phosphor has a uniformly granular shape in triaxial directions.
23. The semiconductor light emitting device according to claim 1 , wherein the red phosphor has a uniformly granular shape in triaxial directions.