Fluorescent substance, method of manufacturing fluorescent substance, and light emitting device using the fluorescent substance

1. A fluorescent substance comprising an alkaline earth metal silicate having a composition represented by the following general formula (1):

(Sr 1-x-y-z Ba x Ca y Eu z ) 2 Si w O 2+2w   (1)

where x, y, z and w fall within the ranges of:

0≦x≦0.97; 0≦y≦0.97;

0.03≦z≦0.20; 1.00<w<1.10.

2. The fluorescent substance according to claim 1 , wherein an emission spectrum of the fluorescent substance as it is excited by light having a wavelength ranging from 360 nm to 500 nm has a single emission band having a peak wavelength of 500 nm to 600 nm.

3. The fluorescent substance according to claim 1 , wherein a largest peak exists at 6970±4 eV when the fluorescent substance is subjected to the XANES analysis.

4. The fluorescent substance according to claim 1 , wherein z in the general formula (1) falls within a range of 0.035 to 0.075.

5. The fluorescent substance according to claim 1 , wherein Eu 2+ is contained in an amount larger than the amount of Eu 3+ in the fluorescent substance.

6. The fluorescent substance according to claim 1 , wherein a crystal structure of the fluorescent substance is an orthorhombic system.

7. A method for manufacturing a europium-activated alkaline earth metal silicate fluorescent substance comprising:

storing a mixture of raw materials into a vessel;

applying a first baking to the mixture of the raw materials under a reducing gas atmosphere of N 2 /H 2 so as to obtain a first baked material;

pulverizing the first baked material to obtain a pulverized first baked material;

storing the pulverized first baked material into a vessel;

placing the vessel storing the pulverized first baked material in a furnace and substituting a nitrogen gas in the furnace under vacuum; and

applying a second baking to the pulverized first baked material under a reducing gas atmosphere of N 2 /H 2 having a hydrogen concentration of 1 to 100% so as to obtain a second baked material.

8. The method according to claim 7 , wherein the first baking is performed at 1,000 to 1,600° C.

9. The method according to claim 7 , wherein the first baking is performed for 3 to 7 hours.

10. The method according to claim 7 , wherein the vacuum denotes a pressure of 1,000 Pa or less.

11. The method according to claim 7 , wherein the second baking is performed at 1,000 to 1,600° C.

12. The method according to claim 7 , wherein the second baking is performed for 2 to 6 hours.

13. A light-emitting device comprising:

a light-emitting element configured to emit a light having a wavelength of 360 nm to 500 nm, and

a layer comprising a fluorescent substance formed on the light-emitting element, the fluorescent substance comprising an alkaline earth metal silicate having a composition represented by the following general formula (1):

(Sr 1-x-y-z Ba x Ca y Eu z ) 2 Si w O 2+2w   (1)

where x, y, z and w fall within the ranges of:

0≦x≦0.97; 0≦y≦0.97;

0.03≦z≦0.20; 1.00<w<1.10.

14. The light-emitting device according to claim 13 , wherein the light-emitting element emits an ultraviolet light or a visible light.

15. The light-emitting device according to claim 13 , wherein the layer comprises the fluorescent substance in an amount of 5 to 50 wt %.

16. The light-emitting device according to claim 13 , wherein z in general formula (1) falls within a range of 0.035 to 0.075.

17. The light-emitting device according to claim 13 , wherein Eu 2+ is contained in an amount larger than the amount of Eu 3+ in the fluorescent substance.

18. The light-emitting device according to claim 13 , wherein a crystal structure of the fluorescent substance is an orthorhombic system.

19. The light-emitting device according to claim 13 , wherein the light-emitting element emits a blue light having a wavelength of 440 nm to 480 nm, and the layer further comprises at least one selected from the group consisting of a fluorescent substance emitting luminescence of yellowish green, a fluorescent substance emitting luminescence of yellow, and a fluorescent substance emitting luminescence of colors ranging from orange to red light.

20. The light-emitting device according to claim 13 , wherein the light-emitting element emits an ultraviolet to violet light having a wavelength of 360 nm to 440 nm, and the layer further comprises at least one selected from the group consisting of a fluorescent substance emitting luminescence of blue, a fluorescent substance emitting luminescence of yellowish green, a fluorescent substance emitting luminescence of yellow, and a fluorescent substance emitting luminescence of colors ranging from orange to red.