Phosphor, method for producing phosphor, phosphor-containing composition, light-emitting device, lighting system and image display device

1. A phosphor containing a crystal phase represented by the following formula [I], wherein when its object color is expressed by the L*a*b* color system, the values of a*, b* and (a* 2 +b* 2 ) 1/2 satisfy −20≦a*≦−2, 71≦b* and 71≦(a* 2 +b* 2 ) 1/2 , respectively:

R 3−x−y−z+w2 M z A 1.5x+y−w2 Si 6−w1−w2 Al w1+w2 O y+w1 N 11−y−w1   [I]

wherein R is at least one rare earth element selected from the group consisting of La, Gd, Lu, Y and Sc; M is at least one metal element selected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb; A is at least one bivalent metal element selected from the group consisting of Ba, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2 represent numerical values within the following ranges, respectively:

(1/7)≦(3 −x−y−z+w 2 )/6<(1/2),

0≦(1.5 x+y−w 2)/6<(9/2),

0 ≦x< 3,

0 ≦y< 2,

0 <z< 1,

0 ≦w 1≦5,

0 ≦w 2≦5,

0 ≦w 1 +w 2≦5.

2. The phosphor according to claim 1 , wherein 0<(1.5x+y−w2)/6<(9/2).

3. The phosphor according to claim 1 , wherein the values of b* and (a* 2 +b* 2 ) 1/2 satisfy 71≦b*≦105 and 71≦(a* 2 +b* 2 ) 1/2 ≦105, respectively.

4. The phosphor according to claim 1 , wherein x is 0<x<3.

5. The phosphor according to claims 1 , wherein 0≦(1.5x+y−w2)<(9/2).

6. The phosphor according to claim 1 , wherein the absorption efficiency is at least 88%.

7. A method for producing a phosphor containing a crystal phase represented by the following formula [I], wherein when its object color is expressed by the L*a*b* color system, the values of a*, b* and (a* 2 +b* 2 ) 1/2 satisfy −20<a*<−2, 71<b* and 71<(a* 2 +b* 2 ) 1/2 , respectively, which comprises nitriding an alloy for production of a phosphor, containing at least elements of R, A and Si, wherein said alloy is subjected to firing in the presence of a flux:

R 3−x−y−z+w2 M z A 1.5x+y−w2 Si 6−w1−w2 Al w1+w2 O y+w1 N 11−y−w1   [I]

wherein R is at least one rare earth element selected from the group consisting of La, Gd, Lu, Y and Sc; M is at least one metal element selected from the group consisting of Ce, Eu, Mn, Yb, Pr and Tb; A is at least one bivalent metal element selected from the group consisting of Ba, Sr, Ca, Mg and Zn; and x, y, z, w1 and w2 represent numerical values within the following ranges, respectively:

(1/7)≦(3 −x−y−z+w 2)/6<(1/2),

0≦(1.5 x+y−w 2)/6<(9/2),

0 ≦x< 3,

0 ≦y< 2,

0 <z< 1,

0 ≦w 1≦5,

0 ≦w 2≦5,

0 ≦w 1 +w 2≦5.

8. The method for producing a phosphor according to claim 7 , wherein 0<(1.5x+y−w2)/6<(9/2).

9. The method for producing a phosphor according to claim 7 , wherein 0≦(1.5x+y−w2)<(9/2).

10. The method for producing a phosphor according to claim 7 , wherein the firing is carried out under a temperature condition such that the rate of temperature rise during the firing is at most 0.5° C./min within a temperature range corresponding to at least a part of the low temperature side of an exothermic peak obtainable by TG-DTA (Thermogravimetry/Differential Thermal Analysis) during the nitriding reaction of the alloy for production of a phosphor.

11. The method for producing a phosphor according to claim 7 , wherein the firing is carried out in a hydrogen-containing nitrogen gas atmosphere.

12. The method for producing a phosphor according to claim 7 , wherein after the firing, the obtained fired product is washed with an acidic aqueous solution.

13. A phosphor containing a composition represented by the following formula [I′], wherein when its object color is expressed by the L*a*b* color system, the values of a*, b* and (a* 2 +b* 2 ) 1/2 satisfy −20≦a*≦−2, 71≦b* and 71≦(a* 2 +b* 2 ) 1/2 , respectively:

(Ln,Ca,Ce) 3+α Si 6 N 11   [I′]

wherein Ln is at least one rare earth element selected from the group consisting of La, Gd, Lu, Y and Sc, and α is a numerical value within a range of −0.1≦α≦1.5.

14. A phosphor-containing composition comprising the phosphor as defined in claim 1 and a liquid medium.

15. A light-emitting device having a first illuminant and a second illuminant which emits visible light under irradiation with light from the first illuminant, wherein the second illuminant contains, as a first phosphor, at least one phosphor selected from the group consisting of the phosphor as defined in claim 1 .

16. The light-emitting device according to claim 15 , wherein the first phosphor has an emission peak wavelength within a wavelength range of from 420 nm to 450 nm.

17. The light-emitting device according to claim 15 , wherein the second illuminant contains, as a second phosphor, at least one phosphor different in the emission peak wavelength from the first phosphor.

18. The light-emitting device according to claim 15 , wherein the first phosphor has an emission peak within a wavelength range of from 420 nm to 500 nm, and the second illuminant contains, as a second phosphor, at least one phosphor having an emission peak within a wavelength range of from 565 nm to 780 nm.

19. The light-emitting device according to claim 15 , wherein the first phosphor has an emission peak within a wavelength range of from 300 nm to 420 nm, and the second illuminant contains, as a second phosphor, at least one phosphor having an emission peak within a wavelength range of from 420 nm to 500 nm.

20. The light-emitting device according to claim 15 , wherein the first phosphor has an emission peak within a wavelength range of from 300 nm to 420 nm, and the second illuminant contains, as a second phosphor, at least one phosphor having an emission peak within a wavelength range of from 420 nm to 500 nm, at least one phosphor having an emission peak within a wavelength range of from 500 nm to 550 nm, and at least one phosphor having an emission peak within a wavelength range of from 565 nm to 780 nm.

21. A lighting system provided with the light-emitting device as defined in claim 15 .

22. An image display device provided with the light-emitting device as defined in claim 15 .