Light-emitting unit having specific fluorescent material

Abstract

A light-emitting device with an emission wavelength range of from 360 nm to 550 nm and a fluorescent material made of Ca—Al—Si—O—N oxynitride activated with Eu 2+ are used so that a part of light emitted from the light-emitting device is emitted while the wavelength of the part of light is converted by the fluorescent material.

1. A light-emitting unit comprising:
 a light-emitting device for emitting light with a wavelength range of from 360 nm to 550 nm; and  
 a fluorescent material comprising Ca—Al—Si—O—N oxynitride activated with Eu 2+ ,  
 wherein at least a part of said light emitted from said light-emitting device is subjected to wavelength conversion by said fluorescent material.  
 
     
     
       2. A light-emitting unit according to  claim 1 , wherein said light-emitting device emits light with a wavelength range of from 450 nm to 550 nm, and wherein said part of said light with the converted wavelength is mixed with the other part of said light emitted from said light-emitting device, so that white light is emitted. 
     
     
       3. A light-emitting unit according to  claim 1 , further comprising:
 a light transmissible material,  
 wherein said fluorescent material comprises one of a powdery material and a granular material and is formed in said light-transmissible material.  
 
     
     
       4. A light-emitting unit according to  claim 1 , wherein said fluorescent material comprises a glassy material. 
     
     
       5. A light-emitting unit according to  claim 1 , wherein said light-emitting device comprises a group III nitride compound semiconductor light-emitting device. 
     
     
       6. A light-emitting unit according to  claim 3 , wherein the light-emitting device is mounted in a cup portion provided in a lead frame, and the cup portion is filled with the light-transmissible material including the fluorescent material. 
     
     
       7. A light-emitting unit according to  claim 3 , wherein the light-emitting device is mounted in a cup portion provided in a lead frame, and a fluorescent layer made from the light-transmissible material including the fluorescent material is provided on a surface of the light-emitting device. 
     
     
       8. A light-emitting unit according to  claim 3 , wherein the light-emitting device is mounted in a cup portion provided in a lead frame, and the light-emitting device and a part of the lead frame are covered with the light-transmissible material including the fluorescent material. 
     
     
       9. A light-emitting unit according to  claim 3 , wherein the light-emitting device is mounted on a substrate, and a fluorescent layer comprising the light-transmissible material including the fluorescent material is provided on a surface of the light-emitting device. 
     
     
       10. A light-emitting unit according to  claim 3 , wherein the light-emitting device is mounted on a substrate, and the light-emitting device is sealed with the light-transmissible material including the fluorescent material. 
     
     
       11. A light-emitting unit according to  claim 3 , wherein the light-emitting device is mounted in a cup portion provided in a substrate, and the cup portion is filled with the light-transmissible material including the fluorescent material. 
     
     
       12. A light-emitting unit according to  claim 3 , wherein the light-emitting device is mounted in a cup portion provided in a substrate, and a fluorescent layer made from the light-transmissible material including the fluorescent material is provided on a surface of the light-emitting device. 
     
     
       13. A light-emitting unit according to  claim 3 , wherein a fluorescent layer made from the light-transmissible material including the fluorescent material is provided on a substrate surface of the light-emitting device. 
     
     
       14. A light-emitting unit according to  claim 3 , wherein a fluorescent layer made form  from the light-transmissible material including the fluorescent material is also provided on a side surface of the light-emitting device. 
     
     
       15. A light-emitting unit according to  claim 3 , wherein a reflection plate is provided in a light-emitting direction of the light-emitting device. 
     
     
       16. A light-emitting unit according to  claim 15 , wherein a fluorescent layer made from the light-transmissible material including the fluorescent material is provided on a surface of the reflection plate opposite to the light-emitting device. 
     
     
       17. A light-emitting unit according to  claim 3 , wherein a fluorescent layer made from the light-transmissible material including the fluorescent material is provided in a light-emitting direction of the light-emitting device. 
     
     
       18. A light-emitting unit according to  claim 17 , further comprising:
 a light guide having a light introduction surface and a light-emitting surface,  
 wherein the light-emitting device is disposed so as to face the light introduction surface of the light guide, and the fluorescent layer is disposed between the light-emitting device and the light introduction surface of the light guide.  
 
     
     
       19. A light-emitting unit according to  claim 17 , further comprising:
 a light guide having a light introduction surface and a light-emitting surface,  
 wherein the light-emitting device is disposed so as to face the light introduction surface of the light guide, and the fluorescent layer is disposed on the light-emitting surface side of the light guide.  
 
     
     
       20. A light-emitting unit according to  claim 19 , further comprising:
 a layer of a light-transmissible material disposed between the light guide and the fluorescent layer.  
 
     
     
       21. A light-emitting unit according to  claim 4 , wherein a fluorescent layer comprising the fluorescent material is provided on a substrate surface of the light-emitting device. 
     
     
       22. A light-emitting unit according to  claim 21 , wherein a fluorescent layer comprising the fluorescent material is also provided on a side surface of the light-emitting device. 
     
     
       23. A light-emitting unit according to  claim 4 , wherein a reflection plate is provided in a light-emitting direction of the light-emitting device. 
     
     
       24. A light-emitting unit according to  claim 23 , wherein the reflection plate comprises the fluorescent material, and a surface of the reflection plate opposite to a surface facing the light-emitting device is planished as a mirror surface. 
     
     
       25. A light-emitting unit according to  claim 4 , wherein a fluorescent layer comprising the fluorescent material is provided in a light-emitting direction of the light-emitting device. 
     
     
       26. A light-emitting unit according to  claim 25 , further comprising:
 a light guide having a light introduction surface and a light-emitting surface,  
 wherein the light-emitting device is disposed so as to face the light introduction surface of the light guide, and the fluorescent layer is disposed between the light-emitting device and the light introduction surface of the light guide.  
 
     
     
       27. A light-emitting unit according to  claim 25 , further comprising:
 a light guide having a light introduction surface and a light-emitting surface,  
 wherein the light-emitting device is disposed so as to face the light introduction surface of the light guide, and the fluorescent layer is disposed on the light-emitting surface side of the light guide.  
 
     
     
       28. A light-emitting unit according to  claim 27 , further comprising:
 a layer of a light-transmissible material disposed between the light guide and the fluorescent layer.  
 
     
     
       29. A light-emitting method comprising:
 irradiating a fluorescent material made of Ca—Al—Si—O—N oxynitride activated with Eu 2+  with light emitted from a light-emitting device with an emission wavelength range of from 360 nm to 550 nm to thereby convert the wavelength of a part of said light; and  
 mixing said part of said light with the converted wavelength with the other part of said light emitted from said light-emitting device to thereby emit resultant light,  
 wherein said light-emitting device is turned on intermittently.  
 
     
     
       30. A light-emitting method according to  claim 29 , wherein the time when said light-emitting device is turned on is adjusted to thereby adjust the color of light emitted from said light-emitting unit. 
     
     
       31. A light-emitting method according to  claim 30 , wherein said light-emitting device emits light with an emission wavelength range of from 480 nm to 550 nm, and wherein said color of said emitted light is white. 
     
     
       32. A light-emitting method according to  claim 29 , wherein said light-emitting device comprises a group III nitride compound semiconductor light-emitting device. 
     
     
       33. A light-emitting unit according to  claim 1 , wherein said fluorescent material has a mean grain size which is not greater than 20 μm. 
     
     
       34. A light-emitting unit according to  claim 1 , wherein said fluorescent material has a mean grain size which is not greater than 10 μm. 
     
     
       35. A light-emitting unit according to  claim 1 , wherein said fluorescent material has a mean grain size which is not greater than 5 μm. 
     
     
       36. A light-emitting unit according to  claim 3 , wherein said light transmissible material comprises one of epoxy resin, silicone resin, urea resin and glass. 
     
     
       37. A fluorescent material for a light-emitting unit, said material comprising Ca—Al—Si—O—N oxynitride activated with Eu 2+ . 
     
     
       38. A light- emitting unit comprising:      a light - emitting device for emitting light with a wavelength range of from  360  nm to  550  nm; and        a fluorescent material comprising an alkaline earth metal, Al, Si and N, and said fluorescent material being activated with a rare earth element,        wherein at least a part of said light emitted from said light - emitting device is subjected to wavelength conversion by said fluorescent material.      
     
     
       39. A light- emitting unit according to    claim 38   , wherein said rare - earth element comprises Eu   2+   .    
     
     
       40. A light- emitting unit according to    claim 38   , wherein said fluorescent material further comprises oxygen.    
     
     
       41. A light- emitting unit according to    claim 38   , wherein said alkaline earth metal comprises calcium.    
     
     
       42. A light- emitting unit according to    claim 38   , further comprising:      a light - transmissible material,        wherein said fluorescent material comprises one of a powdery material and a granular material and is formed in said light - transmissible material.      
     
     
       43. A light- emitting unit according to    claim 42   , wherein said light - transmissible material is formed as a fluorescent layer which is formed in a light - emitting direction of the light - emitting device.    
     
     
       44. A light- emitting unit according to    claim 38   , wherein said light - emitting device emits light with a wavelength range of from  450  nm to  550  nm,      wherein at least a part of said light emitted from said light - emitting device is subjected to wavelength conversion by said fluorescent material, and        wherein said part of said light with the converted wavelength is mixed with the other part of said light emitted from said light - emitting device, such that white light is emitted.      
     
     
       45. A light- emitting unit according to    claim 38   , wherein said light - emitting device comprises a group III nitride compound semiconductor light - emitting device.    
     
     
       46. A light- emitting unit according to    claim 38   , wherein said fluorescent material comprises a mean grain size which is not greater than  20  μm.    
     
     
       47. A light- emitting unit according to    claim 42   , wherein said light - transmissible material comprises one of epoxy resin, silicone resin, urea resin and glass.    
     
     
       48. A method of preparing a fluorescent material for a light- emitting unit, said method comprising:      forming a mixture comprising an alkaline earth metal, Al, Si, N and a rare earth element, and        processing said mixture to obtain said fluorescent material,        wherein an amount of nitrogen in said fluorescent material is controlled to obtain a desired emission wavelength of said fluorescent material.