权利要求：
What is claimed is:
1. An optical film comprising:
a structured top surface comprising a plurality of substantially linear parallel top structures extending along a first direction, each top structure having a cylindrical surface having a radius of curvature R and a height h, h/R not greater than about 0.4; and
a structured bottom surface comprising a plurality of substantially linear parallel spaced apart bottom structures extending along a second direction different from the first direction, each bottom structure comprising opposing first and second faces, the first face being substantially flat, the second face being curved, a spacing between adjacent bottom structures being in a range from about 0.5 microns to about 3 microns.
2. The optical film of claim 1 further comprising a reflective polarizer disposed between the structured top and bottom surfaces, the reflective polarizer substantially reflecting light having a polarization state along a third direction and substantially transmitting light having a polarization state along a fourth direction different from the third direction.
3. The optical film of claim 1, wherein the third direction is along one of the first and second directions and the fourth direction is along the other one of the first and second directions.
4. An optical film comprising a structured surface comprising a plurality of substantially linear parallel structures extending along a first direction, each structure comprising opposing first and second faces extending from respective opposite first and second ends of a base of the structure and meeting at a peak of the structure, such that in a cross-sectional view of the optical film in a direction perpendicular to the first direction, the first face is a piecewise curved arc having a plurality of centers of curvature where at least one is offset from a perpendicular bisector of a line connecting the first end of the base to the peak of the structure.
5. A backlight comprising:
a light source;
a lightguide having an input surface proximate the light source and an output surface; and
the optical film of claim 4 disposed on the outer surface, the structured surface facing the output surface.
6. An optical film comprising:
a structured top surface comprising a plurality of substantially linear parallel top structures extending along a first direction, each top structure comprising opposing first and second substantially flat faces
meeting at a peak of the structure and forming a peak angle, the peak angle in a range from about 90 degrees to about 1 10 degrees; and
a structured bottom surface comprising a plurality of substantially linear parallel bottom structures extending along a second direction different from the first direction, each bottom structure comprising opposing first and second faces extending from respective opposite first and second ends of a base of the structure and meeting at a peak of the structure, such that in a cross-sectional view of the structured bottom surface in a direction perpendicular to the second direction, the first face is substantially a straight line making a first angle with the base in a range from about 50 degrees to about 70 degrees, the second face is an arc having a radius of curvature in a range from about 40 microns to about 100 microns, and a straight line connecting the second end of the base to the peak of the structure makes a second angle with the base in a range from about 60 degrees to about 80 degrees.
7. A backlight comprising:
a light source;
a lightguide having an input surface proximate the light source and an output surface; and
an optical film disposed on the output surface and comprising:
a bottom layer comprising a plurality of substantially linear parallel spaced apart bottom structures extending along a first direction and facing the output surface of the lightguide, a spacing between adjacent bottom structures being in a range from about 0.5 microns to about 3 microns;
a top layer comprising a plurality of substantially linear parallel spaced apart top structures extending along a second direction different from the first direction and facing away from the output surface of the lightguide, a spacing between adjacent top structures being in a range from about 0.5 microns to about 5 microns; and
a reflective polarizer disposed between and adhered to the top and bottom layers, the reflective polarizer substantially reflecting light having a polarization state along a third direction and substantially transmitting light having a polarization state along a fourth direction different from the third direction.
8. The backlight of claim 7, wherein the third direction is along one of the first and second directions and the fourth direction is along the other one of the first and second directions.
9. The backlight of claim 7, wherein the third direction is substantially perpendicular to the fourth direction.
10. The backlight of claim 7, wherein the first direction is substantially perpendicular to the second direction.
11. The backlight of claim 7 further comprising an optical diffuser for diffusing light emitted by the light source disposed on the opposite side of the optical film from the lightguide.
12. The backlight of claim 7, further comprising a buffer layer disposed between the optical film and the lightguide.
13. The backlight of claim 12, wherein the buffer layer includes a top structured surface.
14. The backlight of claim 13, wherein the structured surface of the buffer layer is a surface diffusing structure.
15. The backlight of claim 14, wherein the structured surface of the buffer layer has a higher haze portion and a lower haze portion, and the high haze portion is disposed nearest an edge of the buffer layer proximate the light source.
16. The backlight of claim 15, wherein the high haze portion covers no more than 10% of the top surface of the buffer layer.
17. An optical film comprising:
a structured top surface comprising a plurality of substantially parallel top structures extending linearly along a first direction and arranged with a first pitch; and
a structured bottom surface comprising a plurality of substantially parallel bottom structures extending linearly along a second direction different from the first direction and arranged with a second pitch, a spacing between adjacent bottom structures in a range from about 0.5 microns to about 3 microns, each top and bottom structure comprising opposing first and second faces extending from respective opposite first and second ends of a base of the structure and meeting at a peak of the structure, such that in a cross- sectional view of the structure in a direction perpendicular to the linear extent of the structure, the first and second faces are arcs having a radius of curvature, a ratio of the radius of curvature to the pitch of the structure in a range from about 0.8 to about 10 for each top structure, and about 1.5 to about 20 for each bottom structure.
18. The optical film of claim 17, wherein the structured top surface includes a surface diffusing structure.
19. The optical film of claim 18, wherein the surface diffusing structure has a first slope distribution measured along the first direction and a second slope distribution measured along the second direction, and wherein at least 50% of the magnitude of a first slope distribution is greater than 1 degree.
20. The optical film of claim 19, wherein at least 50% of the magnitude of the second slope distribution is less than 0.1 degrees.
21. The optical film of claim 17, wherein in a cross-sectional view of the structure in a direction perpendicular to the linear extent of the structure, straight lines connecting first and second ends of the base of each structure to the peak of the structure form an angle therebetween in a range from about 60 degrees to about 130 degrees for each top and bottom structure.
22. The optical film of claim 17, wherein an angle between the first and second directions is from about 78 degrees to about 90 degrees.
23. The optical film of claim 17 further comprising a reflective polarizer disposed between the structured top and bottom surfaces, the reflective polarizer substantially reflecting light having a polarization state along a third direction and substantially transmitting light having a polarization state along a fourth direction different from the third direction.
24. The optical film of claim 23, wherein the first direction is substantially perpendicular to the second direction, the third direction is substantially perpendicular to the fourth direction, and one of the first and second directions makes an angle with one of the third and fourth directions between about 0 to 12 degrees.
25. The optical film of claim 17, such that in a cross-sectional view of each bottom structure in a direction perpendicular to the linear extent of the structure, the peak of the structure is an arc having a radius of curvature in a range from about 0.1 microns to about 5 microns.
26. The optical film of claim 25, wherein in a cross-sectional view of each bottom structure in a direction perpendicular to the linear extent of the structure, first and second straight lines going through respective first and second ends of the base of the structure and tangent to respective sides of the curved peak of the structure form an angle therebetween that is in a range from about 50 degrees to about 70 degrees.
27. The optical film of claim 17, wherein in a cross-sectional view of each structure in a direction perpendicular to the linear extent of the structure, a straight line connecting each end of the base of the structure to the peak of the structure forms an angle with the base of the structure between about 5 to 60 degrees for each top structure, and about 25 to 88 degrees for each bottom structure.
28. The optical film of claim 17, wherein in a cross-sectional view of each structure in a direction perpendicular to the linear extent of the structure, a straight line connecting each end of the base of the
structure to the peak of the structure forms an angle with the base of the structure between about 30 to 50 degrees for each top structure, and about 50 to 70 degrees for each bottom structure.
29. The optical film of claim 17, wherein in a cross-sectional view of each top and bottom structure in a direction perpendicular to the linear extent of the structure, straight lines connecting first and second ends of the base of the structure to the peak of the structure make a same angle with the base of the structure.
30. The optical film of claim 17, wherein in each cross-sectional view of each structure in a direction perpendicular to the linear extent of the structure, a straight line connecting each end of the base of the structure to the peak of the structure makes an angle with the base of the structure between about 35 to 45 degrees for each top structure and about 55 to 65 degrees for each bottom structure.
31. The optical film of claim 17, such that in a cross-sectional view of each top and bottom structure in a direction perpendicular to the linear extent of the structure, any radius of curvature at the peak of the structure is smaller than the radius of curvature of the first and second faces of the structure.
32. The optical film of claim 17, such that in each cross-sectional view of each top and bottom structure in a direction perpendicular to the linear extent of the structure, the first and second faces of the structure are arcs not having a same center of curvature.
33. The optical film of claim 17, wherein each of the first and second pitches is between about 10 to 100 microns.
34. The optical film of claim 17, wherein each of the first and second pitches is between about 10 to 50 microns.
35. The optical film of claim 17, wherein in a cross-sectional view of each structure in a direction perpendicular to the linear extent of the structure, the first and second faces of the structure have a same radius of curvature.
36. The optical film of claim 17, wherein in a cross-sectional view of each structure in a direction perpendicular to the linear extent of the structure, the radius of curvature is between about 20 to 40 microns for each top structure, and about 60 to 80 microns for each bottom structure. 37. The optical film of claim 17, wherein in a cross-sectional view of each structure in a direction perpendicular to the linear extent of the structure, the ratio of the radius of curvature of the first and
second faces of the structure to the pitch of the structure is between about 1 to about 3 for each top structure, and about 2 to about 5 for each bottom structure.
38. The optical film of claim 17, wherein a height of at least one structure in the pluralities of top and bottom structures varies along a linear extent of the structure.
39. The optical film of claim 17, wherein the plurality of substantially parallel top structures are arranged with a variable first pitch. 40. The optical film of claim 17, wherein the plurality of substantially parallel bottom structures are arranged with a variable second pitch.
41. The optical film of claim 17 further comprising an optical diffuser for diffusing light. 42. The optical film of claim 17 further comprising a quarter wavelength layer.
43. The optical film of claim 42, wherein the quarter wavelength layer is disposed between the structured top and bottom surfaces. 44. The optical film of claim 42, wherein the quarter wavelength layer is disposed on the structured top surface opposite the structured bottom surface.
45. The optical film of claim 17 further comprising a polarization management optical stack comprising: a reflective polarizer substantially reflecting light having a polarization state along a third direction and substantially transmitting light having a polarization state along a fourth direction different from the third direction; and
a quarter wavelength layer.
46. The optical film of claim 45, wherein the reflective polarizer is adhered to the quarter wavelength layer.
47. The optical film of claim 45, wherein the polarization management optical stack is disposed on the structured top surface opposite the structured bottom surface, the quarter wavelength layer disposed between the reflective polarizer and the structured top surface.
48. The optical film of claim 45, wherein the polarization management optical stack is disposed between the structured top and bottom surfaces, the quarter wavelength layer disposed between the reflective polarizer and the structured top surface. 49. The optical film of claim 45, wherein the polarization management optical stack is disposed between the structured top and bottom surfaces, the quarter wavelength layer disposed between the reflective polarizer and the structured bottom surface.
50. The optical film of claim 45 further comprising an optically birefringent substrate disposed between the structured top and bottom surfaces.
51. A backlight comprising:
a light source;
a lightguide having an input surface proximate the light source and an output surface; and
the optical film of claim 17 disposed on the outer surface, the structured bottom surface facing the output surface.
52. A backlight comprising:
a light source;
a lightguide having an input surface proximate the light source and an output surface; and
an optical film disposed on the output surface and comprising:
a first structured surface comprising a plurality of substantially linear parallel first structures extending along a first direction and facing the output surface of the lightguide;
a second structured surface comprising a plurality of substantially linear parallel second structures extending along a second direction different from the first direction and facing away from the output surface of the lightguide, each first and second structure comprising opposing curved first and second faces extending from respective opposite first and second ends of a base of the structure and meeting at a peak of the structure, the curved first and second faces having different axes of curvature; and
a reflective polarizer substantially reflecting light having a polarization state along a third direction and substantially transmitting light having a polarization state along a fourth direction different from the third direction, such that at least 10% of light emitted by the light source and exiting the backlight is recycled by the second structured surface before exiting the backlight.
53. The backlight of claim 52, wherein the lightguide comprises a back surface opposite the output surface, and wherein the backlight further comprises a reflective layer disposed adjacent the back surface of the lightguide.
54. A multilayer optical film comprising:
an optically birefringent substrate;
a plurality of substantially parallel top structures disposed on the optically birefringent substrate and extending linearly along a first direction;
a plurality of substantially parallel bottom structures disposed on the optically birefringent substrate opposite the top structures and extending linearly along a second direction different from the first direction;
a reflective polarizer disposed between the top structures and the birefringent substrate, the reflective polarizer substantially reflecting light having a polarization state along a third direction and substantially transmitting light having a polarization state along a fourth direction different from the third direction; and
a quarter wavelength layer disposed between the top structures and the reflective polarizer; wherein each top and bottom structure comprises opposing curved first and second faces extending from respective opposite first and second ends of a base of the structure and meeting at a peak of the structure, the curved first and second faces having different axes of curvature.