Light-emitting device, white light-emitting device, illuminator, and image display
View Patent ↗To achieve a light-emitting device emitting light with high brightness, closer to natural light, and less color shift due to a small change in intensity of emitted light, in a light-emitting device including a light source emitting light by driving current and at least one wavelength-converting material absorbing at least part of the light from the light source and emitting light having a different wavelength, the color coordinate x 1 (17.5) and the color coordinate y 1 (17.5) of the light emitted at a driving current density of 17.5 A/cm 2 and the color coordinate x 1 (70) and the color coordinate y 1 (70) of the light emitted at a driving current density of 70 A/cm 2 satisfy the following Expressions (D) and (E): −0.006≦ x 1 (17.5)− x 1 (70)≦0.006 (D), −0.006≦ y 1 (17.5)− y 1 (70)≦0.006 (E).
1. A white light emitting device comprising:
a light source configured to emit light; and
at least one wavelength converting-material configured to absorb at least a part of the light emitted from the light source and configured to emit light having different wavelengths,
wherein the white-light emitting device emits white light comprising the light emitted by the wavelength-converting material,
a maximum intensity of an emission spectrum of the white light at a wavelength range of 500 nm to 650 nm is not higher than 150% of a minimum intensity in the wavelength range, and
said wavelength converting-material comprises at least one green phosphor and comprises at least one red phosphor represented by formula (3):
M a A b D c E d X e (3)
where M is one or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm and Yb; A represents one or two elements selected from the group consisting of divalent metallic elements other than the M; D represents one or more elements selected from the group consisting of quadrivalent metallic elements; E represents one or more elements selected from the group consisting of trivalent metallic elements; X represents one or more elements selected from the group consisting of 0, N, and F; and a, b, c, d, and e are numbers satisfying:
0.00001≦a≦0.1,
a+b=1,
0.5≦c≦4,
0.5≦d≦8,
0.8×(⅔+ 4/3×c+d)≦e, and
e≦1.2×(⅔+ 4/3×c+d).
2. The white light emitting device according to claim 1 , wherein c and d in the formula (3) satisfy:
0.5 ≦c≦ 1.8, and
0.5 ≦d≦ 1.8.
3. The white light emitting device according to claim 1 , wherein a luminance of said green phosphor in 100° C. is 80% or more of a luminance of said green phosphor in 25° C.
4. The white light emitting device according to claim 1 , wherein said green phosphor is at least one selected from the group consisting of an oxide, a nitride, and an oxynitride.
5. The white light emitting device according to claim 1 , wherein said green phosphor is at least one green phosphor selected from the group consisting of MSi 2 N 2 O 2 2:Eu, M-Si—Al—O—N:Ce, M-Si—Al—O—N:Eu (where M represents one or more alkaline earth metals), and a phosphor which comprises at least Ce as a luminescence center ion in a host crystal represented by formula (1) or (2),
M 1 a M 2 b M 3 c O d (1)
where M 1 represents a divalent metallic element, M 2 represents a trivalent metallic element, M 3 represents a quadrivalent metallic element, and a, b, c, d, and e are numbers satisfying:
2.7≦a≦3.3,
1.8≦b≦2.2,
2.7≦c≦3.3, and
11.0≦d≦13.0;
M 4 e M 5 f O g (2)
where M 4 represents a divalent metallic element, M 5 represents a trivalent metallic element, and e, f, and g are numbers satisfying:
0.9≦e≦1.1,
1.8≦f≦2.2, and
3.6≦g≦4.4.
6. The white light emitting device according to claim 1 , wherein a general color rendering index Ra prescribed in JIS-Z8726 is 90 or greater.
7. The white light emitting device according to claim 1 , wherein a brightness of the wavelength-converting material at 100° C. is not less than 80% of a brightness at 25° C.
8. The white light emitting device according to claim 1 , wherein an absorption efficiency of the wavelength-converting material for a light with a peak wavelength emitted by the light source is 50% or more, and an internal quantum efficiency of the wavelength-converting material is 40% or more.
9. A lighting system comprising:
the white light emitting device according to claim 1 .
10. The white light emitting device according to claim 1 , wherein the green phosphor comprises at least one of Ca 3 Sc 2 Si 3 O 12 :Ce and Mg-activated Ca 3 Sc 2 Si 3 O 12 :Ce.
11. The white light emitting device according to claim 1 , wherein the green phosphor is Ca 3 Sc 2 Si 3 O 12 :Ce.
12. The white light emitting device according to claim 1 , wherein the green phosphor is Mg-activated Ca 3 Sc 2 Si 3 O 12 :Ce.
13. The white light emitting device according to claim 1 , wherein the green phosphor comprises at least one of Ca 2.97 Ce 0.03 Se 1.97 Mg 0.03 Si 3 O 12 , Ca 2.97 Ce 0.03 Sc 1.94 Mg 0.06 Si 3 O 12 , Ca 2.94 Ce 0.03 Sc 1.94 Mg 0.06 Si 3 O 12 , Ca 2.94 Ce 0.06 Sc 1.97 Mg 0.03 Si 3 O 12 , Ca 2.94 Ce 0.06 Sc 1.94 Mg 0.06 Si 3 O 12 , Ca 2.94 Ce 0.06 S 1.9 Mg 0.1 Si 3 O 12 , Ca 2.9 Ce 0.1 Sc 1.97 Mg 0.03 Si 3 O 12 , and Ca 2.9 Ce 0.1 Sc 1.94 Mg 0.06 Si 3 O 12 .
14. The white light emitting device according to claim 1 , wherein the green phosphor comprises at least one of Ce 0.01 Ca 0.99 Sc 2 O 4 , Ce 0.007 Ca 0.993 Sc 2 O 4 , and Ce 0.013 Ca 0.987 Sc 2 O 4 .
15. The white light emitting device according to claim 1 , wherein the green phosphor comprises at least one of Ce 0.01 Ca 0.94 Sr 0.05 Se 2 O 4 , Ce 0.01 Ca 0.89 Sr 0.1 Sc 2 O 4 , and Ce 0.01 Ca 0.84 Sr 0.15 Sc 2 O 4 .
16. The white light emitting device according to claim 1 , wherein in the formula (3), X represents N.
17. The white light emitting device according to claim 1 , wherein in the formula (3), X represents a mixture of O and N.
18. The white light emitting device according to claim 1 , wherein the wavelength converting-material is a mixture of Ca 3 Sc 2 Si 3 O 12 :Ce and CaAlSiN 3 :Eu.