Light emitting device, vehicle headlamp, illumination device, and vehicle

• US 9,625,121 B2
• Filed: 11/15/2011
• Issued: 04/18/2017
• Est. Priority Date: 12/01/2010
• Status: Active Grant

• Current Assignee: Sharp Fukuyama Laser Co., Ltd. (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Fukai, Yasuo, Takahira, Yoshiyuki, Takahashi, Koji, Maemura, Yosuke, Tomomura, Yoshitaka
• Primary Examiner(s): Coughlin, Andrew
• Assistant Examiner(s): GARLEN, ALEXANDER K
• Application Number:
  US13/297,008
• Publication Number:
  US 20120140504A1
• Time in Patent Office: 1,981 Days
• Field of Search: 362 84, 362260, 362509, 362510, 362516, 362547, 362294
• CPC Class Codes: F21S 41/16 Laser light sources
• CPC Class Codes: F21S 41/176 Light sources where the light is generated by photoluminescent material spaced from a primary light generating element
• CPC Class Codes: F21S 45/47 Passive cooling, e.g. using fins, thermal conductive elements or openings
• CPC Class Codes: F21V 9/30 Elements containing photoluminescent material distinct from or spaced from the light source shades F21V1/17; globes, bowls or cover glasses F21V3/08, F21V3/12; refractors F21V5/10; reflectors F21V7/26, F21V7/30; elements with provision for controlling the spectral properties or intensity F21V9/40

Abstract

A headlamp 1 includes (i) a laser element 2 for emitting a laser beam, (ii) a light emitting section 4, including a sealing material made from an inorganic material, for emitting fluorescence upon receiving the laser beam emitted from the laser element 2, and (iii) a heat sink 7 for releasing, via a contact surface of the heat sink 7 which contact surface is in contact with the light emitting section 4, heat generated in the light emitting section 4 in response to the laser beam emitted onto the light emitting section 4, the light emitting section 4 existing within a range which is determined on the basis of the contact surface and with which desired heat releasing efficiency is obtained.

Claims

1. A light emitting device comprising:

an excitation light source for emitting excitation light;

a light emitting section, including a sealing material made from an inorganic material, for emitting fluorescence upon receiving the excitation light emitted from the excitation light source; and

a heat releasing section having a contact surface and a bottom surface opposite from the contact surface, the contact surface of the heat releasing section being in contact with the light emitting section for releasing heat generated in the light emitting section in response to the excitation light emitted onto the light emitting section,

wherein the light emitting section and the heat releasing section are provided so that the light emitting section is located entirely within a range of 0.2 mm or less from the contact surface,

the excitation light source is a semiconductor laser and provided on a side of the bottom surface with respect to the heat releasing section,

the heat releasing section is made of a rigid transparent material,

the excitation light passes through the heat releasing section so that the light emitting section is irradiated with the excitation light, and

the heat releasing section is placed between the excitation light source and the light emitting section so that the excitation light enters a light incident surface of the light emitting section and fluorescent light is released from a surface of the light emitting section, which is opposite from the light incident surface.

2. The light emitting device as set forth in claim 1, wherein:

the contact surface has recesses and protrusions.

3. The light emitting device as set forth in claim 1, wherein:

the light emitting section includes, in its inside, a heat conductive member capable of conducting heat to the heat releasing section.

4. The light emitting device as set forth in claim 1, wherein:

the light emitting section has a surface on which a heat conductive member is provided, at least one end of the heat conductive member extending to the heat releasing section.

5. The light emitting device as set forth in claim 1, wherein:

the heat releasing section has a plurality of through-holes arranged in a lattice pattern; and

the light emitting section comprises a plurality of light emitting sections, and the plurality of light emitting sections are provided in the plurality of through-holes.

6. The light emitting device as set forth in claim 1, wherein:

the heat releasing section has a plurality of recesses arranged in a lattice pattern; and

the light emitting section comprises a plurality of light emitting sections, and the plurality of light emitting sections are provided in the plurality of recesses.

7. The light emitting device as set forth in claim 1, wherein:

the contact surface is in contact with a plurality of surfaces of the light emitting section.

8. The light emitting device as set forth in claim 1, wherein:

the contact surface is in contact with an irradiated surface of the light emitting section onto which irradiated surface the excitation light is emitted; and

at least a part of the heat releasing section is made from a high reflectance material which reflects the fluorescence emitted from the light emitting section, said part of the heat releasing section being the contact surface.

9. The light emitting device as set forth in claim 1, wherein:

the heat releasing section has a light-transmitting section which is in contact with the light emitting section; and

the fluorescence is emitted from the light emitting section via the light-transmitting section.

10. The light emitting device as set forth in claim 3, wherein:

a percentage of (i) an area of the heat conductive member appearing on a fluorescence emitting surface of the light emitting section with respect to (ii) an area of the fluorescence emitting surface is 40% or less, the fluorescence emitting surface facing another surface of the light emitting section, the another surface of the light emitting section being in contact with the contact surface, and the fluorescence being emitted from the light emitting section via the fluorescence emitting surface.

11. The light emitting device as set forth in claim 4, wherein:

a percentage of (i) an area of the heat conductive member appearing on said surface of the light emitting section with respect to (ii) an area of said surface of the light emitting section is 40% or less, said surface not including a surface of the light emitting section which surface is in contact with the contact surface.

12. The light emitting device as set forth in claim 3, wherein:

the heat conductive member has higher heat conductivity than that of the sealing material which is included in the light emitting section in order to seal a fluorescent material.

13. The light emitting device as set forth in claim 3, wherein:

the heat conductive member is made from a transparent material.

14. The light emitting device as set forth in claim 5, wherein:

in a surface of the heat releasing section, a total area of the plurality of through-holes is 1.5 times or more larger than a total area of a region by which the plurality of through-holes are separated from each other.

15. The light emitting device as set forth in claim 6, wherein:

in a surface of the heat releasing section, a total area of the plurality of recesses is 1.5 times or more larger than a total area of a region by which the plurality of recesses are separated from each other.

16. The light emitting device as set forth in claim 1, wherein:

a relative positional relationship between the light emitting section and the heat releasing section is set so that a temperature of the light emitting section is 300°

C. or lower when the excitation light has an excitation density which is within a range from 0.94 W/mm² to 3.2 W/mm².

17. A vehicle headlamp comprising a light emitting device recited in claim 1.

18. An illumination device comprising a light emitting device recited in claim 1.

19. A vehicle comprising a vehicle headlamp,

the vehicle headlamp including:

an excitation light source for emitting excitation light;

a light emitting section, including a sealing material made from an inorganic material, for emitting fluorescence upon receiving the excitation light emitted from the excitation light source;

a reflecting mirror having a reflecting curved surface for reflecting the fluorescence emitted from the light emitting section; and

a heat releasing section having a contact surface and a bottom surface opposite from the contact surface, the contact surface of the heat releasing section being in contact with the light emitting section for releasing heat generated in the light emitting section in response to the excitation light emitted onto the light emitting section,

wherein the light emitting section and the heat releasing section are provided so that the light emitting section is located entirely within a range of 0.2 mm or less from the contact surface,

the excitation light source is a semiconductor laser and provided on a side of the bottom surface with respect to the heat releasing section,

the heat releasing section is made of a rigid transparent material,

the excitation light passes through the heat releasing section so that the light emitting section is irradiated with the excitation light,

the vehicle headlamp is mounted in the vehicle so that the reflecting curved surface is located on a lower side in a vertical direction, and

the heat releasing section is placed between the excitation light source and the light emitting section so that the excitation light enters a light incident surface of the light emitting section and fluorescent light is released from a surface of the light emitting section, which is opposite from the light incident surface.