Uniform white color light diffusing fiber

Abstract

Light diffusing optical fibers for use in illumination applications and which have a uniform color gradient that is angularly independent are disclosed herein along with methods for making such fibers. The light diffusing fibers are composed of a silica-based glass core that is coated with a number of layers including both a scattering layer and a phosphor layer.

We claim: 
     
       1. A light diffusing fiber for emitting white light comprising:
 a) a core formed from a silica-based glass;   b) a cladding in direct contact with the core;   c) a scattering layer in direct contact with the cladding; and   d) a phosphor layer surrounding and in direct contact with the scattering layer, wherein the color of the light emitted, as measured by the CIE 1931 x, y chromacity space, comprises x from about 0.20 to about 0.30 and y from 0.26 to about 0.35.   
     
     
       2. The light diffusing fiber of  claim 1 , wherein x is from about 0.23 to about 0.28 and y is from about 0.28 to about 0.33. 
     
     
       3. The light diffusing fiber of  claim 1 , wherein the color of the light emitted falls within the claimed CIE 1931 x, y values for all viewing angles from about 15° to about 170° relative to the direction of the light diffusing optical fiber. 
     
     
       4. The light diffusing fiber of  claim 1 , wherein the light diffusing optical fiber emits light having an intensity along the fiber that does not vary by more than about 20%. 
     
     
       5. The light diffusing fiber of  claim 1 , wherein the scattering induced attenuation loss comprises from about 0.1 dB/m to about 50 dB/m at a wavelength of 550 nm. 
     
     
       6. The light diffusing fiber of  claim 1 , wherein the core comprises a plurality of randomly distributed voids. 
     
     
       7. The light diffusing fiber of  claim 1 , wherein the cladding comprises a polymer. 
     
     
       8. The light diffusing fiber of  claim 7 , wherein the polymer comprises CPC6. 
     
     
       9. The light diffusing fiber of  claim 1 , wherein the scattering layer comprises a polymer. 
     
     
       10. The light diffusing fiber of  claim 9 , wherein the polymer comprises CPC6. 
     
     
       11. The light diffusing fiber of  claim 1 , wherein the scattering layer comprises a plurality of randomly distributed voids or microparticles or nanoparticles of a scattering material. 
     
     
       12. The light diffusing fiber of  claim 11 , wherein the microparticles or nanoparticles comprise TiO 2  or SiO 2 . 
     
     
       13. The light diffusing fiber of  claim 1 , further comprising a light emitting device that emits light with a wavelength from about 300 nm to about 450 nm into the core of the light diffusing fiber. 
     
     
       14. The light diffusing fiber of  claim 1 , wherein the phosphor layer comprises microparticles or nanoparticles of an inorganic phosphorescent or fluorescent material. 
     
     
       15. The light diffusing fiber of  claim 14 , wherein the inorganic phosphorescent or fluorescent material comprises CeYAG, NdYAG, quantum dots, or nanoparticles. 
     
     
       16. The light diffusing fiber of  claim 1 , further comprising a secondary layer in between the cladding and scattering layer. 
     
     
       17. A method of producing the light diffusing fiber of  claim 1  comprising:
 a) forming an optical fiber preform comprising a preform core; 
 b) drawing the optical fiber preform into an optical fiber; 
 c) coating the optical fiber with at least one cladding layer; 
 d) coating the optical fiber with at least one scattering layer; and 
 e) coating the optical fiber with at least one phosphor layer. 
 
     
     
       18. A light emitting device for emitting white light comprising:
 a light diffusing fiber, comprising:
 a core formed from a silica-based glass; 
 a cladding in direct contact with the core; and 
 a single layer comprising a phosphor layer and a scattering medium in direct contact with the cladding, and 
   a light source that emits a high energy light with a wavelength from about 300 nm to about 550 nm into the core of the light diffusing fiber,   wherein the white light comprises a combination of a scattered light and a scattered fluorescent or phosphorescent light, and is uniform in color as a function of viewing angle; and   wherein the scattering medium comprises a plurality of randomly distributed voids or microparticles or nanoparticles of a scattering material.    
     
     
       19. The light emitting device of claim 18, wherein the high energy light source has a wavelength in a range from about 300 nm to about 450 nm.  
     
     
       20. The light emitting device of claim 18, wherein the color of the white light, as measured by the CIE 1931 x, y chromacity space, comprises x from about 0.15 to about 0.30 and y from about 0.20 to about 0.35, and wherein the color of the white light falls within the claimed CIE 1931 x, y values for all viewing angles from about 15° to about 170° relative to the direction of the light diffusing optical fiber.  
     
     
       21. The light emitting device of claim 18, wherein the color of the white light, as measured by the CIE 1931 x, y chromacity space, comprises x from about 0.20 to about 0.30 and y from 0.26 to about 0.35.  
     
     
       22. The light emitting device of claim 18, wherein the light diffusing optical fiber emits light having an intensity along the fiber that does not vary by more than about 20%.  
     
     
       23. The light emitting device of claim 18, further comprising a scattering induced attenuation loss from about 0.1 dB/m to about 50 dB/m at a wavelength of 550 nm.  
     
     
       24. The light emitting device of claim 18, wherein the core comprises a plurality of randomly distributed voids.  
     
     
       25. The light emitting device of claim 18, wherein either one of or both the cladding and the single layer comprises a polymer.  
     
     
       26. The light emitting device of claim 18, wherein the phosphor layer comprises microparticles or nanoparticles of an inorganic phosphorescent or fluorescent material.  
     
     
       27. The light emitting device of claim 26, wherein the inorganic phosphorescent or fluorescent material comprises CeYAG, NdYAG, quantum dots, or nanoparticles.