Fluorescent material having two layer structure and light emitting apparatus employing the same

• US 7,560,859 B2
• Filed: 09/13/2005
• Issued: 07/14/2009
• Est. Priority Date: 09/14/2004
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), Masafumi Harada, Mitsuru Funato, Shizuo Fujita, Yoichi Kawakami
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), Masafumi Harada, Mitsuru Funato, Shizuo Fujita, Yoichi Kawakami
• Inventors: Saito, Hajime, Kawakami, Yoichi, Harada, Masafumi, Fujita, Shizuo, Fujita, legal representative, Funato, Mitsuru, Fujita, Shigeo, Morioka, Tatsuya
• Primary Examiner(s): Tom; Toan
• Assistant Examiner(s): HANLEY, BRITT D
• Application Number:
  US11/224,131
• Publication Number:
  US 20060158089A1
• Time in Patent Office: 1,400 Days
• US Class Current: 313/498
• CPC Class Codes: C09K 11/02 Use of particular materials as binders, particle coatings or suspension media therefor
• CPC Class Codes: C09K 11/62 containing gallium, indium or thallium
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01S 5/0087 for illuminating phosphorescent or fluorescent materials, e.g. using optical arrangements specifically adapted for guiding or shaping laser beams illuminating these materials
• CPC Class Codes: H01S 5/0225 Out-coupling of light
• CPC Class Codes: H01S 5/0232 Lead-frames
• CPC Class Codes: H01S 5/32341 blue laser based on GaN or GaP
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y10S 977/774 Exhibiting three-dimensional carrier confinement, e.g. quantum dots

Abstract

A fluorescent material excellent in emission efficiency in white emission and a light-emitting apparatus employing this fluorescent material and having excellent color rendering are provided with a fluorescent material comprising a two-layer structure of a core of a particle size having a quantum effect and a shell covering this core in which the ground state energy of the core is in the range of 1.85 to 2.05 eV, the high order energy of the core is not in the ranges of 2.3 to 2.5 eV and 2.65 to 2.8 eV, or the ground state energy of the core is in the range of 2.3 to 2.5 eV, the high order energy of the core is not in the range of 2.65 to 2.8 eV an light-emitting apparatus employing these fluorescent materials.

Claims

1. A fluorescent material comprising a two-layer structure of a core of a particle size having a quantum effect and a shell covering said core, wherein

particle size of the core and composition ratio of the fluorescent material are such that the ground state energy of said core is in the range of 2.3 to 2.5 eV and the high order energy of said core is not in the ranges of 2.65 to 2.8 eV,

said fluorescent material coloring red with a peak wavelength of 500 to 540 nm by light absorption.

2. The fluorescent material according to claim 1, wherein the band gap of said shell is larger than 2.8 eV.

3. The fluorescent material according to claim 1, wherein the particle size of said core is not more than twice the Bohr radius.

4. The fluorescent material according to claim 1, wherein the particle size of said shell is at least 1 μ

m.

5. The fluorescent material according to claim 1, wherein

the surface of said shell is coated or adsorbed with a material different from the materials of said shell and said core.

6. The fluorescent material according to claim 5, wherein said material for coating or adsorbing the surface of said shell is an inorganic oxide.

7. The fluorescent material according to claim 1, wherein

said core is made of a group III-V compound semiconductor containing at least In or a group II-VI compound semiconductor containing at least Zn.

8. The fluorescent material according to claim 7, wherein

said shell is made of a group III nitride semiconductor containing at least Ga or a group II-VI compound semiconductor containing at least Zn.

9. The fluorescent material according to claim 8, wherein both said core and shell are made of In_xGa₁₋

xN (0 ≦

x≦

1).

10. A light-emitting apparatus comprising a red fluorescent material and a green fluorescent material homogeneously dispersed in a medium for presenting white emission as a whole by absorbing blue excitation light with said red fluorescent material and said green fluorescent material and generating secondary light, wherein

said red fluorescent material comprises a two-layer structure of a core of a particle size having a quantum effect and a shell covering said core, wherein particle size of the core and composition ratio of the fluorescent material are such that the ground state energy of said core is in the range of 1.85 to 2.05 eV, and the high order energy of said core is not in the ranges of 2.3 to 2.5 eV and 2.65 to 2.8 eV, and

said green fluorescent material comprises a two-layer structure of a core of a particle size having a quantum effect and a shell covering said core, wherein praticle size of the core and composition ratio of the fluorescent material are such that the ground state energy of said core is in the range of 2.3 to 2.5 eV, and the high order energy of said core is not in the range of 2.65 to 2.8 eV.

11. The light-emitting apparatus according to claim 10, further comprising a light-emitting device, having a peak wavelength in the range of 380 to 420 nm, made of a group III nitride semiconductor or a group II-VI compound semiconductor as a light source emitting said excitation light.

12. The light-emitting apparatus according to claim 10, including a blue fluorescent material, comprising a two-layer structure of a core of a particle size having a quantum effect and a shell covering said core with the ground state energy of said core in the range of 2.65 to 2.8 eV, in said medium.

13. The light-emitting apparatus according to claim 10, wherein said medium contains at least any material selected from epoxy resin, silicon resin, polycarbonate resin and acrylic resin.

14. The light-emitting apparatus according to claim 10, wherein said medium is glass.

15. The light-emitting apparatus according to claim 10, wherein said medium includes a light diffusion material scattering and color-mixing primary light and/or said secondary light.

16. The light-emitting apparatus according to claim 10, further comprising a reflector provided oppositely to said medium through a light source emitting said excitation light for reflecting said excitation light and/or said secondary light.

17. The light-emitting apparatus according to claim 10, further comprising an optical film provided between a light source emitting said excitation light and said medium for transmitting said excitation light while blocking said secondary light.

18. The light-emitting apparatus according to claim 17, wherein said optical film blocks ultraviolet light having a wavelength of less than 380 nm.