Light-redirecting optical structures

• US 20040246599A1
• Filed: 04/23/2004
• Published: 12/09/2004
• Est. Priority Date: 05/02/2003
• Status: Active Grant

• Current Assignee: Orafol Americas Inc. (Orafol Europe GmbH), ZF Lemforder Metallwaren AG
• Original Assignee: Reflexite
• Inventors: Nilsen, Robert B.
• Granted Patent: US 7,330,315 B2
• Time in Patent Office: Days
• US Class Current: 359/831
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer

Abstract

A plurality of microstructures is provided, with each microstructure having at least a first side and at least a second side terminating at a peak. At least some of the peaks can include an elevated portion to space the peaks away from adjacent optical sheets, surfaces, films, substrates, or other layers to minimize wet-out, Newton'"'"'s rings, abrasions, moire fringes, or other undesirable optical conditions. In other embodiments, an optical film is also provided that includes a first plurality of microstructures having a base, a first side, and a second side, and a second plurality of microstructures having a base, a first side, and a second side, the first side including a first planar surface, and the second side including a second planar surface and a third planar surface.

Claims

1. A plurality of microstructures, each microstructure having at least a first side and at least a second side terminating at a peak, at least some of the peaks including an elevated portion extending above the peaks.

2. The microstructures of claim 1, wherein the plurality of microstructures is designed to redirect light in a collimating fashion.

3. The microstructures of claim 1, wherein the elevated portions extend above the peaks to space an adjacent surface away from the peaks to reduce visible defects.

4. The microstructures of claim 3, wherein the elevated portions space the adjacent surface away from the peaks by at least about 0.3 micrometers.

5. The microstructures of claim 1, wherein the microstructures form part of a rear-projection screen, a computer display or monitor, an overhead projection display, or a liquid crystal display.

6. The microstructures of claim 1, wherein the microstructures have a series of base planes and a series of plateaus at a window side of the microstructures, the base planes and the plateaus running along a first axis, the plateaus and base planes alternating along a second axis, the plateaus not being coplanar with the base planes.

7. The microstructures of claim 6, wherein at least some of the plateaus include an elevated portion extending above the plateaus.

8. The microstructures of claim 1, wherein the microstructures include linear prisms, prisms, pyramids, truncated pyramids, lenticulars, cones, moth-eye structured surfaces, diffractive structures, diffractive structured surfaces, textured surfaces, lenses, base planes and plateaus, and/or lens arrays.

9. The microstructures of claim 1, further comprising a microstructure pattern provided on a window side of the microstructures.

10. The microstructures of claim 9, wherein at least some areas of the window side include an elevated portion extending above the window side.

11. The microstructures of claim 1, wherein a differentially-cured pattern is formed on and/or within a window side of the microstructures.

12. The microstructures of claim 11, wherein the pattern is formed by placing a mask over the window side of the microstructures, the mask including opaque areas and transparent areas, and curing the prisms with a radiation source, wherein the opaque areas block the radiation to cause the area of the windows underneath the opaque areas to be cured at a different amount of time or rate than the area underneath the transparent areas, resulting in the pattern.

13. The microstructures of claim 1, further comprising a moth-eye structured surface provided on a window side of the microstructures.

14. The microstructures of claim 13, wherein at least some areas of the window side include an elevated portion extending above the window side.

15. The microstructures of claim 1, wherein the microstructures have an included angle of between about 60 and 120 degrees.

16. An optical film including a plurality of microstructures, at least some of the microstructures including differential height locators.

17. The optical film of claim 16, wherein the film is configured to redirect light in a collimating fashion.

18. The optical film of claim 16, wherein the differential height locators space the optical film away from an adjacent film, surface, or structure.

19. The optical film of claim 18, wherein the adjacent film, surface, or structure includes at least one of a light-redirecting film, collimating film, abrasion reduction layer, light guide, polarizing structure, or a diffuser.

20. The optical film of claim 16, wherein the microstructures are used to collimate light.

21. The optical film of claim 16, wherein the microstructures form part of a rear-projection screen, a computer display or monitor, an overhead projection display, or a liquid crystal display.

22. The optical film of claim 16, wherein the microstructures have a series of base planes and a series of plateaus at a window side of the microstructures, the base planes and the plateaus running along a first axis, the plateaus and base planes alternating along a second axis, the plateaus not being coplanar with the base planes.

23. The optical film of claim 16, further comprising a differentially-cured pattern provided on a window side of the microstructures.

24. The optical film of claim 16, wherein the microstructures include linear prisms, prisms, pyramids, truncated pyramids, lenticulars, cones, moth-eye structured surfaces, diffractive structures, diffractive structured surfaces, textured surfaces, lenses, polarizing surfaces, base planes and plateaus, and/or lens arrays.

25. The optical film of claim 16, wherein a microstructure pattern is provided on a window side of the microstructures.

26. The optical film of claim 16, wherein a differentially-cured pattern is formed on and/or within a window side of the microstructures.

27. An optical film comprising:

a first plurality of microstructures having a base, a first side, and a second side; and

a second plurality of microstructures, which is different than the first plurality, having a base, a first side, and a second side, the first side including a first planar surface, and the second side including a second planar surface and a third planar surface.

28. The optical film of claim 27, wherein the film includes at least a first zone that includes the first plurality of microstructures and at least a second zone that includes the second plurality of microstructures.

29. The optical film of claim 28, wherein the first zone and the second zone alternate along the film.

30. The optical film of claim 27, wherein peaks of the first plurality of microstructures extend above peaks of the second plurality of microstructures.

31. The optical film of claim 30, wherein the peaks of the first plurality of microstructures extend above the peaks of the second plurality of microstructures by at least about 0.3 micrometers.

32. The optical film of claim 27, wherein the first, second, and third planar surfaces each have a different cross-sectional length.

33. The optical film of claim 32, wherein the second plurality of microstructures includes a base and wherein the first side includes the first planar surface extending from the base to a fourth planar surface, the fourth planar surface extending to the second planar surface at an apex of the microstructures.

34. The optical film of claim 27, wherein the first plurality of microstructures has an included angle between the first side and the second side of about 90 degrees.

35. The optical film of claim 27, wherein the second plurality of microstructures has an included angle between the first planar surface and the second planar surface of between about 60 and 120 degrees.

36. The optical film of claim 27, wherein the second planar surface and the third planar surface are concave-shaped as viewed in cross-section.

37. The optical film of claim 27, wherein the second planar surface and the third planar surface are convex-shaped as viewed in cross-section.

38. The optical film of claim 27, wherein the film includes a first cured portion and a second cured portion which are formed from a same radiation-curable material, the first cured portion being cured to a first amount of time or rate and the second cured portion being cured to a second amount of time or rate, the first amount of time or rate being sufficiently different than the second amount of time or rate to result in a discontinuity on the surface of the structure.

39. A microstructure having a first side and a second side terminating at a linear apex, wherein at least one section of the apex extends above the linear apex.

40. The microstructure of claim 39, wherein the at least one section is rounded.

41. The microstructure of claim 39, wherein the at least one section is elongate.

42. An optical film comprising:

a plurality of microstructures oriented in a first direction; and

at least one structure extending above peaks of the microstructures, the at least one structure being randomly positioned on the film.

43. The optical film of claim 42, further comprising differentially-cured patterns provided on a window side of the film.

44. An optical structure comprising:

an optical layer; and

a plurality of microstructures each having at least a first side and a second side terminating at a peak, peaks of the microstructures being spaced sufficiently away from the optical layer by spacing elements on at least some of the peaks to prevent or minimize an undesirable optical condition.

45. The optical structure of claim 44, wherein the optical layer includes a diffuser.

46. The optical structure of claim 44, wherein the plurality of microstructures is a first plurality of microstructures, the optical structure further comprising a second plurality of microstructures positioned below the first plurality of microstructures.

47. The optical structure of claim 46, wherein the second plurality of microstructures is offset relative to the first plurality of microstructures.

48. The optical structure of claim 46, further comprising a diffuser positioned below the second plurality of microstructures.

49. The optical structure of claim 48, further comprising a waveguide positioned below the diffuser.

50. The optical structure of claim 44, wherein the plurality of microstructures is a first plurality of microstructures, further comprising a second plurality of microstructures, the second plurality of microstructures having a base, a first side, and a second side, the first side including a first planar surface, and the second side including a second planar surface and a third planar surface.

51. The optical structure of claim 50, wherein peaks of the first plurality of microstructures extend above peaks of the second plurality of microstructures to space peaks of the second plurality of microstructures away from the optical layer to prevent or minimize an undesirable optical condition.

52. A method of forming a pattern on a film, comprising:

(a) facing a surface of a drum until the surface is substantially smooth;

(b) engraving a negative image of the pattern in the surface of the drum;

(c) refacing and re-engraving the surface of the drum, if necessary, until the negative image of the pattern is a desired depth in the surface of the drum; and

(d) casting, with the surface of the drum, the pattern on the film.

53. The method of claim 52, further comprising casting the pattern on a window side of the film.

54. The method of claim 52, wherein structures in the pattern have a height in the range of between about 0.010 and 3.00 micrometers.