Light-emitting device and phosphor
View Patent ↗The present invention provides a light-emitting device having an excitation source which emits a light having a wavelength of from 420 to 500 nm and a phosphor in combination, and having a high luminance. A light-emitting device having a first illuminant which emits a light having a wavelength of 420 to 500 nm and a second illuminant which emits a visible light when irradiated with the light from the first illuminant, characterized in that the second illuminant contains a phosphor, and the object color of the phosphor satisfies L*≧90, −22≦a*≦−10, and b*≧55, in the L*, a*, b* color system.
1. A light-emitting device having a first illuminant which emits a light having a wavelength of 420 to 500 nm and a second illuminant which emits a visible light when irradiated with the light from the first illuminant, wherein the second illuminant comprises a phosphor, and the object color of the phosphor satisfies L*≧90, −22≦a*≦−10, and b*≧55, in the L*, a*, b* color system and the emission intensity at 100° C. of the phosphor is at least 90% of the emission intensity at 25° C.,
wherein the phosphor is an oxide having a garnet structure and comprises Ce, or Ce and Tb, and at least one element selected from the group consisting of Y, Gd, Sc, Lu and La.
2. The light-emitting device according to claim 1 , wherein the 1/10 afterglow time (t 1 ) of the phosphor is at least 155 ns, and/or the ratio (t 2 /t 1 ) of the 1/100 afterglow time (t 2 ) to the 1/10 afterglow time, is at least 2.05.
3. The light-emitting device according to claim 1 , wherein the first illuminant is a laser diode or a light-emitting diode.
4. The light-emitting device according to claim 3 , wherein the first illuminant is a light-emitting diode.
5. The light-emitting device according to claim 1 , wherein the first illuminant employs a GaN type compound semiconductor.
6. The light-emitting device according to claim 1 , wherein the first illuminant is a surface-emitting GaN type laser diode.
7. The light-emitting device according to claim 1 , wherein the second illuminant is in a film form.
8. The light-emitting device according to claim 7 , wherein the film surface of the second illuminant is contacted directly to the emission surface of the first illuminant.
9. The light-emitting device according to claim 1 , wherein the second illuminant contains another phosphor, and the light-emitting device emits white light.
10. The light-emitting device according to claim 1 , wherein the second illuminant is one having a powder of the phosphor dispersed in a resin.
11. The light-emitting device according to claim 1 , which is an illumination device.
12. An image display device comprising, as a light-emitting source, the light-emitting device according to claim 1 .
13. The light-emitting device according to claim 1 , wherein the object color of the phosphor satisfies b*≧65.
14. The light-emitting device according to claim 1 , wherein the phosphor comprises a crystal phase having a chemical composition of the following formula [1]:
(Ln 1-a-b Ce a Tb b ) 3 M 5 O 12 Formula [1]
wherein Ln is at least one element selected from the group consisting of Y, Gd, Sc, Lu and La, M is at least one element selected from the group consisting of Al, Ga and In, and a and b are numbers which satisfy 0.001≦a≦0.3, and 0≦b≦0.5, respectively.