Totally internally reflecting thin, flexible film

Abstract

A thin, flexible film made of a transparent polymeric material including a structured surface and an opposite smooth surface, wherein light striking either surface, within certain angular ranges, is totally internally reflected. The structured surface includes a linear array of miniature substantially right angled isosceles prisms arranged side-by-side to form a plurality of peaks and grooves. In addition, the perpendicular sides of the prims make an angle of approximately 45° with the smooth surface, and when the film is curled the smooth surface lies in a smooth continuous arcuate curve without materially affecting the performance of the film. Because of the film's flexibility and its ability to totally internally reflect light, it may be utilized in a variety of ways, for example, as a collector of solar energy or as a light conduit. The performance of the film may be manipulated to permit controlled light leakage.

1. A thin, flexible film of a transparent polymeric material, comprising a structured surface on one side and a smooth surface opposite said structured surface on the other side, said structured surface includes a linear array of miniature isosceles prisms having substantially perpendicular sides arranged side-by-side to form a plurality of peaks and grooves said film having at least 40 of said prisms per inch, the perpendicular sides of said prisms make an angle of approximately 45° with said smooth surface opposite said structured surface, said film being capable of being curled such that said smooth surface lies in a smooth continuous arcuate curve having a diameter of approximately 18 inches. 
     
     
       2. The film defined in  claim 1 , wherein the film does not have sufficient strength to be self-supporting. 
     
     
       3. The film defined in  claim 1 , wherein said transparent polymeric material is polycarbonate. 
     
     
       4. The film defined in  claim 1 , wherein said transparent polymeric material is acrylic. 
     
     
       5. The film defined in  claim 1 , wherein incident light striking the smooth surface within certain angular ranges is totally internally reflected. 
     
     
       6. The film defined in  claim 1 , wherein incident light striking the structured surface within certain angular ranges is totally internally reflected. 
     
     
       7. The film defined in  claim 1  wherein said film has a thickness of approximately 0.015 of an inch and about 70 prisms per inch so that when said film is curled said smooth surface lies in a smooth continuous arcuate curve without any discernible discontinuities. 
     
     
       8. A thin, flexible film of a transparent polymeric material, comprising a structured surface on one side and a smooth surface opposite said structured surface on the other side, said structured surface includes a linear array of miniature isosceles prisms having substantially perpendicular sides arranged side-by-side to form a plurality of peaks and grooves, the perpendicular sides of said prisms make an angle of approximately 45° with said smooth surface opposite said structured surface, said film being capable of being curled such that said smooth surface lies in a smooth continuous arcuate curve having a diameter of approximately 18 inches and said film does not have sufficient strength to be self-supporting. 
     
     
       9. The film of  claim 1  wherein said transparent polymeric material is polyurethane. 
     
     
       10. The film of  claim 1  wherein said transparent polymeric material has a high refractive index. 
     
     
       11. The film of  claim 1  wherein said transparent polymeric material has a refractive index greater than or equal to  1 . 493 . 
     
     
       12. The film of  claim 1  wherein said transparent polymeric material has a refractive index greater than or equal to  1 . 586 . 
     
     
       13. The film of  claim 1 ,  3 ,  4 , or  9  wherein said transparent polymeric material is isotropic. 
     
     
       14. The film of  claim 1 ,  3 ,  4 , or  9  wherein said transparent polymeric material is homogeneous. 
     
     
       15. The film of  claim 1  wherein the film diffuses light. 
     
     
       16. The film of  claim 1  wherein the film comprises an optical modification to permit controlled light leakage. 
     
     
       17. The film of  claim 16  wherein the optical modification comprises diffusing particles. 
     
     
       18. The film of  claim 16  wherein the optical modification comprises a window. 
     
     
       19. The film of  claim 16  wherein the optical modification comprises said prisms having non- optically sharp corners.   
     
     
       20. The film of  claim 16  wherein the optical modification comprises said prisms having non- optically smooth perpendicular sides.   
     
     
       21. The film of  claim 16  wherein the optical modification comprises rounding said peaks of the structured surface, said rounding defined in accordance with the ratio r/ρ, where r is the approximate radius of the round peaks and ρ is the groove period. 
     
     
       22. The film of  claim 1  wherein the film comprises a composite structure in which the prisms are bonded to a separate sheet material. 
     
     
       23. The film of  claim 1  wherein the film has about  70  prisms per inch so that when said film is curled said smooth surface lies in a smooth continuous arcuate curve without any discernible discontinuities. 
     
     
       24. The film of  claim 1  wherein the film is self- supporting.   
     
     
       25. The film of  claim 1  in combination with a light source arranged to direct incident light upon one of the structured or smooth surfaces of the film such that the light within certain angular ranges is totally internally reflected upon striking the other of the structured or smooth surfaces. 
     
     
       26. The film of  claim 8  wherein said transparent polymeric material is polyurethane. 
     
     
       27. The film of  claim 8  wherein said transparent polymeric material is acrylic. 
     
     
       28. The film of  claim 8  wherein said transparent polymeric material is polycarbonate. 
     
     
       29. The film of  claim 8  wherein said transparent polymeric material has a high refractive index. 
     
     
       30. The film of  claim 8  wherein said transparent polymeric material has a refractive index greater than or equal to  1 . 493 . 
     
     
       31. The film of  claim 8  wherein said transparent polymeric material has a refractive index greater than or equal to  1 . 586 . 
     
     
       32. The film of  claim 8 ,  26 ,  27 , or  28  wherein said transparent polymeric material is isotropic. 
     
     
       33. The film of  claim 8 ,  26 ,  27 , or  28  wherein said transparent polymeric material is homogeneous. 
     
     
       34. The film of  claim 8  wherein the film diffuses light. 
     
     
       35. The film of  claim 8  wherein the film comprises an optical modification to permit controlled light leakage. 
     
     
       36. The film of  claim 35  wherein the optical modification comprises diffusing particles. 
     
     
       37. The film of  claim 35  wherein the optical modification comprises a window. 
     
     
       38. The film of  claim 35  wherein the optical modification comprises said prisms having non- optically sharp corners.   
     
     
       39. The film of  claim 35  wherein the optical modification comprises said prisms having non- optically smooth perpendicular sides.   
     
     
       40. The film of  claim 35  wherein the optical modification comprises rounding said peaks of the structured surface, said rounding defined in accordance with the ratio r/ρ, where r is the approximate radius of the round peaks and ρ is the groove period. 
     
     
       41. The film of  claim 8  wherein the film comprises a composite structure in which the prisms are bonded to a separate sheet material. 
     
     
       42. The film of  claim 8  wherein the film has about  70  prisms per inch so that when said film is curled said smooth surface lies in a smooth continuous arcuate curve without any discernible discontinuities. 
     
     
       43. The film of  claim 8  in combination with a light source arranged to direct incident light upon one of the structured or smooth surfaces of the film such that the light within certain angular ranges is totally internally reflected upon striking the other of the structured or smooth surfaces.