Wavelength conversion member and light-emitting device

1. A wavelength conversion member comprising:

phosphors made of (i) phosphor particles which are made of at least one of an oxynitride and a nitride and have a refractive index n 1 , and (ii) a coating which coats each of said phosphor particles and has a refractive index n 2 said coating having multiple layers including an yttrium oxide, a magnesium oxide, an aluminum oxide, and a silicon oxide arranged on said phosphor particles in this order; and

a medium having said phosphors dispersed therein and having a refractive index n 3 ,

wherein the refractive index n 2 of the coating is a value between n 3 and n 1 .

2. The wavelength conversion member according to claim 1 , wherein the refractive index n 2 of said coating varies in a stepwise manner in a direction from a surface of each of the phosphor particles to an interface with the medium.

3. The wavelength conversion member according to claim 1 , wherein said phosphor particles made of the oxynitride are phosphor particles each containing, as compositional elements, Si, Al, O, N, and at least one or two types of lanthanoid-based rare-earth elements.

4. The wavelength conversion member according to claim 1 , wherein said phosphor particles made of the nitride are phosphor particles each containing, as compositional elements, Ca, Si, Al, N, and at least one or two types of lanthanoid-based rare-earth elements.

5. The wavelength conversion member according to claim 1 , wherein the entire film thickness of said coating is not less than 5 nm and not more than 3 μm.

6. The wavelength conversion member according to claim 1 , wherein said coating is formed by a sol-gel method.

7. The wavelength conversion member according to claim 1 , wherein said medium is made of silicone resin.

8. The wavelength conversion member according to claim 1 , wherein said medium is made of glass.

9. The wavelength conversion member according to claim 1 , wherein said medium has

a first type of the phosphors having a fluorescence peak wavelength of not less than 400 nm and less than 500 nm,

a second type of the phosphors having a fluorescence peak wavelength of not less than 500 nm and less than 600 nm, and

a third type of the phosphors having a fluorescence peak wavelength of not less than 600 nm and not more than 700 nm dispersed therein.

10. The wavelength conversion member according to claim 1 , comprising

a first wavelength conversion member layer in which said phosphors having a fluorescence peak wavelength of not less than 400 nm and less than 500 nm are dispersed in said medium,

a second wavelength conversion member layer in which said phosphors having a fluorescence peak wavelength of not less than 500 nm and less than 600 nm are dispersed in said medium, and

a third wavelength conversion member layer in which said phosphors having a fluorescence peak wavelength of not less than 600 nm and not more than 700 nm are dispersed in said medium.

11. A light-emitting device, comprising: a semiconductor light-emitting element; and the wavelength conversion member according to claim 1 , arranged to allow light emitted by said semiconductor light-emitting element to be incident thereon.

12. The light-emitting device according to claim 11 , wherein

a third wavelength conversion member layer in which said phosphors having a fluorescence peak wavelength of not less than 600 nm and not more than 700 nm are dispersed in said medium,

a second wavelength conversion member layer in which said phosphors having a fluorescence peak wavelength of not less than 500 nm and less than 600 nm are dispersed in said medium, and

a first wavelength conversion member layer in which said phosphors having a fluorescence peak wavelength of not less than 400 nm and less than 500 nm are dispersed in said medium

are arranged such that the light emitted by said semiconductor light-emitting element is made incident on the third, second, and first wavelength conversion member layers in this order.

13. The light-emitting device according to claim 11 , wherein

a second wavelength conversion member layer in which said phosphors having a fluorescence peak wavelength of not less than 500 nm and less than 600 nm are dispersed in said medium,

a third wavelength conversion member layer in which said phosphors having a fluorescence peak wavelength of not less than 600 nm and not more than 700 nm are dispersed in said medium, and

a first wavelength conversion member layer in which said phosphors having a fluorescence peak wavelength of not less than 400 nm and less than 500 nm are dispersed in said medium

are arranged such that the light emitted by said semiconductor light-emitting element is made incident on the second, third, and first wavelength conversion member layers in this order.

14. The light-emitting device according to claim 11 , wherein said semiconductor light-emitting element has an emission peak wavelength of not less than 370 nm and not more than 480 nm.

15. The light-emitting device according to claim 11 , wherein said semiconductor light-emitting element is a semiconductor light-emitting element made of a GaN-based semiconductor.

16. The light-emitting device of claim 1 , wherein said coating having multiple layers includes only the yttrium oxide, the magnesium oxide, the aluminum oxide, and the silicon oxide arranged on said phosphor particles in this order.

17. The light-emitting device of claim 1 , wherein the yttrium oxide is provided directly on said phosphor particles.