Illumination apparatus and film

• US 7,452,120 B2
• Filed: 02/05/2007
• Issued: 11/18/2008
• Est. Priority Date: 03/24/2006
• Status: Expired due to Fees

• Current Assignee: SKC Haas Display Films Co., Ltd. (Dow, Inc.)
• Original Assignee: Rohm and Haas Denmark Finance A/S
• Inventors: Lee, Junwon, Rankin, Charles M. Jr., Wilson, Randall H., Meissner, Stephen C.
• Primary Examiner(s): TSO, LAURA K
• Application Number:
  US11/671,070
• Publication Number:
  US 20070223247A1
• Time in Patent Office: 652 Days
• Field of Search: 362/618, 362/627, 362/606, 362/607, 362/326, 362/330, 362/332, 362/639, 362/308, 362/309, 362/222, 362/223, 362/329
• US Class Current: 362/627
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 2202/28 Adhesive materials or arrangements

Abstract

An illumination apparatus comprises:

• • (a) at least one light source;
  • (b) a light guide for accepting light from the at least one light source and for guiding the light using total internal reflection, the light guide having a top surface;
  • (c) a light extracting film having an input surface optically coupled with the top surface and an output surface for providing light,
  • wherein the input surface comprises a plurality of features which are optically coupled to the top surface of the light guide, such features having:
    • (i) a first side comprising two or more planar segments; and
    • (ii) a second side comprising two or more planar segments, and
  • wherein either the length of at least some of the features is less than the width of the film or the first and second sides intersect at an apex.

Claims

1. An illumination apparatus comprising:

(a) at least one light source;

(b) a light guide for accepting light from the at least one light source and for guiding the light using total internal reflection, the light guide having a top surface;

(c) a light extracting film having an input surface optically coupled with the top surface and an output surface for providing light,

wherein the input surface comprises a plurality of light extracting features which are optically coupled to the top surface of the light guide, at least some light extracting features having;

(i) a first side comprising two or more planar segments; and

(ii) a second side comprising two or more planar segments, and wherein the first and second sides intersect at an apex.

2. The illumination apparatus of claim 1 wherein the light extracting features are optically coupled to the light guide by being partially embedded in an optical adhesive.

3. The illumination apparatus of claim 2 wherein the area of optical coupling is a function of the area of the light extracting feature in contact with the optical adhesive.

4. The illumination apparatus of claim 2 wherein there is present a material in contact with both the optical adhesive and the light extracting features that has a relatively low refractive index compared to that of the adhesive and the light extracting features in order to allow total internal reflection (TIR) on the surface of the light extracting features.

5. The illumination apparatus of claim 4 wherein the relatively low refractive index material is air.

6. The illumination apparatus of claim 1 wherein the light extracting features have a longitudinal axis and wherein each of at least two of the features extends in the direction of its longitudinal axis, and wherein their respective longitudinal axes are substantially in parallel with each other and in parallel with the plane of the top surface of the light guide.

7. The illumination apparatus of claim 1 wherein all or part of the apexes of intersection of the first and second sides lie along a line parallel to the plane of the top surface of the light guide.

8. The illumination apparatus of claim 1 wherein the angle θ

3 formed at the apex of intersection is in the range of 61 degrees to 120 degrees.

9. The illumination apparatus of claim 1 wherein an optical contact ratio between the light guide and the light extracting film is greater over a central portion of the light guide than over an end portion.

10. The illumination apparatus of claim 2 wherein the index of refraction of the adhesive differs from the index of refraction of the features by no more than 0.02.

11. The illumination apparatus of claim 1 wherein the light guide has a bottom surface opposite the top surface, the bottom surface comprising a plurality of microstructures that are substantially elongated in one direction.

12. The illumination apparatus of claim 11 wherein the microstructures are prismatic, arcuate, semi-circular, conic, aspheric, trapezoidal, or a composite of at least two shapes in cross-section.

13. The illumination apparatus of claim 1 additionally comprising additional optically functional layers.

14. The illumination apparatus of claim 13 wherein the additional layers comprise a diffuser, a polarizer, or a brightness enhancer.

15. The illumination apparatus of claim 1 wherein the light extracting film is also a diffusing film.

16. The illumination apparatus of claim 15 wherein the light extracting film is rendered diffusive by the presence of a diffusive coating.

17. The illumination apparatus of claim 15 wherein the light extracting film is rendered diffusive by the presence of a diffusive substrate.

34. The illumination apparatus of claim 2 wherein, for at least two of the light extracting features, the apex is in contact with the light guide.

18. A light extracting film having an input surface for being optically coupled with the top surface of a light guide and an output surface for providing light, wherein the input surface comprises a plurality of light extracting features, each light extracting feature comprising:

(i) a first side comprising two or more planar segments; and

(ii) a second side comprising two or more planar segments,

wherein the first and second sides intersect at an apex, and at least two of the light extracting features have lengths that are much smaller than the dimension of the light extracting film measured in the same direction.

19. The light extracting film of claim 18 wherein at least two of the light extracting features have different lengths.

20. The light extracting film of claim 18 wherein the light extracting features have end portions that are sloped or curved.

21. The light extracting film of claim 18 wherein, for at least one light extracting feature, the first and second sides are substantially bilaterally symmetrical.

22. The light extracting film of claim 18 wherein the light extracting features are attached to a film substrate.

23. A display apparatus comprising:

(a) at least one light source;

(b) a light guide for accepting light from the at least one light source and for guiding the light using total internal reflection, the light guide having a top surface;

(c) a light extracting film having an input surface optically coupled with the top surface and an output surface for providing light; and

(d) a light gating device for modulating the light to form an image thereby,

wherein the input surface comprises a plurality of light extracting features which are optically coupled to the top surface of the light guide, each light extracting feature having;

(i) a first side comprising two or more planar segments; and

(ii) a second side comprising two or more planar segments, and wherein the first and second sides intersect at an apex.

24. An illumination apparatus comprising:

(a) at least one light source;

(b) a light guide for accepting light from the at least one light source and for guiding the light using total internal reflection;

(c) a light extracting film having an input surface optically coupled with the light guide and an output surface parallel to the input surface for providing light,

wherein the input surface comprises a plurality of light extracting features which are optically coupled to the light guide, such features being extended in a longitudinal direction and having a cross section in the plane perpendicular to the longitudinal direction, the cross section comprising

(i) a first side comprising at least two but not more than six linear segments, and

(ii) a second side comprising at least two but not more than six linear segments,

wherein at least one of the plurality of light extracting features has a length measured in the longitudinal direction that is less than the length of the light extracting film measured in the longitudinal direction.

25. The illumination apparatus of claim 24 wherein the first and second sides intersect at an apex.

26. The illumination apparatus of claim 24 wherein the first and second sides intersect in a curved surface.

27. The illumination apparatus of claim 24 wherein the first and second sides intersect at a small rounded or chamfered tip.

28. The illumination apparatus of claim 24 wherein the lengths of at least two of the light extracting features are at least 100 times shorter than the length of the light extracting film measured in the same direction.

29. The illumination apparatus of claim 24 further comprising an adhesive layer for coupling the light extracting film to the light guide.

30. The illumination apparatus of claim 24 wherein the slope from each linear segment to the next linear segment varies by more than 7 degrees.

31. The illumination apparatus of claim 24 further comprising a microstructured layer disposed on the light guide opposite the light extracting film, wherein the microstructured layer comprises a plurality of microstructures extending in a direction perpendicular to the longitudinal direction.

32. The illumination apparatus of claim 24 wherein an optical contact ratio between the light guide and the light extracting film varies in the longitudinal direction.

33. The illumination apparatus of claim 24 wherein the cross section is substantially constant over the length of the optical contact region of each light extracting feature.