Brightness enhancement film using a linear arrangement of light concentrators

• US 20050270798A1
• Filed: 06/03/2004
• Published: 12/08/2005
• Est. Priority Date: 06/03/2004
• Status: Active Grant

• Current Assignee: SKC Hi-Tech & Marketing Co., Ltd.
• Original Assignee: Eastman Kodak Company
• Inventors: Kessler, David, Lee, Junwon
• Granted Patent: US 7,160,017 B2
• Time in Patent Office: Days
• US Class Current: 362/607
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects

Abstract

A brightness enhancement article (30) provides light from a two-dimensional surface. The brightness enhancement article (30) has a plurality of light collecting structures (32), wherein each light collecting structure (32) is longitudinally extended in a length direction along the surface. Each light collecting structure (32) has an input aperture (33) optically coupled to a light-providing surface and an output aperture (35) distal from the input aperture (33), wherein the output aperture (35) has a surface area that is larger than the surface area of the input aperture (33). A pair of curved side walls (38) extend from the output aperture (35) toward the input aperture (33). In a cross section taken orthogonally with respect to the length direction, the curved side walls (38) approximate a parabolic curvature.

Claims

1. A brightness enhancement article for providing light from a surface, the brightness enhancement article comprising:

a plurality of light collecting structures, wherein each light collecting structure is longitudinally extended in a length direction along the light-providing surface,

each light collecting structure comprising;

(a) an input aperture optically coupled to the light-providing surface;

(b) an output aperture distal from said input aperture, wherein the output aperture has a surface area that is larger than the surface area of the input aperture; and

,

(c) a pair of curved side walls extending along the length direction and extended from the output aperture toward the input aperture;

wherein, in a cross section taken orthogonally with respect to the length direction, the curved side walls approximate a parabolic curvature.

2. A brightness enhancement article according to claim 1 wherein the length direction is substantially parallel to the axis of a light bulb that provides source illumination.

3. A brightness enhancement article according to claim 1 wherein adjacent light collecting structures are disposed substantially in parallel with respect to each other.

4. A brightness enhancement article according to claim 1 wherein the light-providing surface and at least one light collecting structure are the same material.

5. A brightness enhancement article according to claim 1 wherein the width of the output aperture varies over the length of the light collecting structure.

6. A brightness enhancement article according to claim 1 wherein the pitch between adjacent light collecting structures is substantially equal.

7. A brightness enhancement article according to claim 1 wherein the pitch between adjacent light collecting structures is varied.

8. A brightness enhancement article according to claim 1 wherein light collecting structures are arranged substantially radially with respect to a light source.

9. A brightness enhancement article according to claim 1 wherein adjacent lengths of the light collecting structure are arranged to follow a curved path.

10. A brightness enhancement article according to claim 1 wherein adjacent lengths of the light collecting structure are arranged to follow a path of varying curvature.

11. A brightness enhancement article according to claim 1 wherein the curved side walls provide total internal reflection to direct light incident at the input aperture to the output aperture.

12. A substrate for enhancing luminance from a light-providing surface, the substrate comprising:

a ribbed surface for collecting off-axis light,

the ribbed surface formed by a series of spaced-apart grooves defining,

between successive grooves, longitudinally extended ribs,

each rib having, in cross-sectional profile, curved side walls tapered from an output aperture to an input aperture, wherein the output aperture has a surface area that is larger than the surface area of the input aperture;

wherein, in a cross section taken orthogonally with respect to a longitudinally extended rib, the curved side walls approximate a parabolic curvature.

13. A substrate according to claim 12 wherein the off-axis light is provided by a light guiding plate.

14. A substrate according to claim 12 wherein the pitch between the spaced-apart grooves is varied along the ribbed surface of the substrate.

15. A substrate according to claim 12 wherein a plurality of the longitudinally extended ribs follow a non-linear path.

16. A substrate according to claim 12 wherein at least one of the longitudinally extended ribs follows a non-linear path.

17. A substrate according to claim 12 wherein the input aperture is optically coupled to a light guiding plate.

18. A substrate according to claim 17 wherein index of refraction of the substrate is substantially equal to the index of refraction of the light guiding plate.

19. A substrate according to claim 12 wherein, for at least one rib, the width of the output aperture varies by more than 10% over the length of the rib.

20. An illumination system comprising:

(a) a light providing element having an output surface;

(b) a brightness enhancement article comprising a plurality of light collecting structures, wherein each light collecting structure is longitudinally extended in a length direction along the output surface of the light providing element, each light collecting structure comprising;

(i) an input aperture optically coupled to the output surface of the light-providing element;

(ii) an output aperture distal from the input aperture, wherein the output aperture has a surface area that is larger than the surface area of the input aperture; and

,

(iii) a pair of curved side walls extending from the output aperture toward the input aperture;

wherein, in a cross section taken orthogonally with respect to the length direction, the curved side walls approximate a parabolic curvature;

(c) a reflective surface, along at least a portion of the surface of the light providing element opposite the output surface, for reflecting light back into the light providing element; and

,

(d) a prism surface optically coupled with the surface of the light providing element and opposite the output surface, the prism surface comprising prism structures longitudinally extended in a width direction, the width direction being substantially orthogonal to the length direction of the brightness enhancement article.

21. An illumination system according to claim 20, further comprising a light conditioning article for conditioning light provided from the brightness enhancement article.

22. An illumination system according to claim 21 wherein the light conditioning article comprises a reflective polarizer.

23. An illumination system according to claim 21 wherein the light conditioning article comprises a diffuser.

24. An illumination system according to claim 20 wherein adjacent light collecting structures are disposed substantially in parallel with respect to each other.

25. An illumination system according to claim 20 wherein the output surface and at least one light collecting structure are the same material.

26. An illumination system according to claim 20 wherein the width of the output aperture varies by more than 10% over the length of at least one light collecting structure.

27. illumination system according to claim 20 wherein the pitch between adjacent light collecting structures is substantially equal.

28. An illumination system according to claim 20 wherein the pitch between any two adjacent light collecting structures is varied by more than 10% over the length of the brightness enhancement article.

29. An illumination system according to claim 20 wherein light collecting structures are arranged substantially radially with respect to a light source.

30. An illumination system according to claim 20 wherein adjacent lengths of the light collecting structure are arranged to follow a curved path.

31. An illumination system according to claim 20 wherein adjacent lengths of the light collecting structure are arranged to follow a path of varying curvature.

32. A display apparatus comprising:

(a) a light providing surface;

(b) a brightness enhancement article coupled with the light providing surface to provide backlight illumination, the brightness enhancement article comprising;

a plurality of light collecting structures, wherein each light collecting structure is longitudinally extended in a length direction along the surface,

each light collecting structure comprising;

(i) an input aperture optically coupled to the light-providing surface;

(ii) an output aperture distal from said input aperture, wherein the output aperture has a surface area that is larger than the surface area of the input aperture; and

,

(iii) a pair of curved side walls extending from the output aperture toward the input aperture;

wherein, in a cross section taken orthogonally with respect to said length direction, the curved side walls approximate a parabolic curvature;

and,

(c) a display panel for modulating the backlight illumination to form an image.

33. An illumination system according to claim 32 wherein the display panel comprises an LCD.

34. An illumination system according to claim 32 further comprising a light conditioning article for conditioning light provided from the brightness enhancement article.

35. An illumination system according to claim 34 wherein the light conditioning article comprises a reflective polarizer.

36. An illumination system according to claim 34 wherein the light conditioning article comprises a diffuser.

37. A method for enhancing on-axis brightness of a backlighting illumination system comprising:

forming a plurality of light collecting structures, wherein each light collecting structure is longitudinally extended in a length direction along a light-providing surface, each light collecting structure comprising;

(i) an input aperture optically coupled to the light-providing surface;

(ii) an output aperture distal from said input aperture, wherein the output aperture has a surface area that is larger than the surface area of the input aperture; and

,

(iii) a pair of curved side walls extending from the output aperture toward the input aperture;

wherein, in a cross section taken orthogonally with respect to said length direction, the curved side walls approximate a parabolic curvature.

38. The method of claim 37 wherein the cross-sectional parabolic curvature in y-z orthogonal axis space is defined by:

(1) determining a range of a variable angle φ

of input light from the light-collecting surface, based on

π

/2−

sin<sup>−

1</sup>(1/n)≦

φ

π

/2

wherein n approximates the index of refraction of the substrate of the brightness enhancement article;

(2) defining an input aperture dimension r_i;

(3) defining a maximum output beam angle θ

_m relative to a normal at the output aperture;

(4) for the range of variable angle φ

, calculating y-z coordinates for the parabolic curvature outline using;

$\begin{array}{c}y<br><br>\left(\mathrm{\varphi <br><br>};<br><br>{\mathrm{\theta <br><br>}}_m,{\mathrm{\theta <br><br>}}_r\right)=\frac{2<br><br>f<br><br>\text{\hspace{1em}<br><br>}<br><br>\sin <br><br>\left(\mathrm{\varphi <br><br>}-{\mathrm{\theta <br><br>}}_r\right)}{1-\cos <br><br>\left(\mathrm{\varphi <br><br>}+{\mathrm{\theta <br><br>}}_m\right)}+r_i<br><br>\left[2<br><br>\cos <br><br>\left({\mathrm{\theta <br><br>}}_r\right)-1\right]\\ z<br><br>\left(\mathrm{\varphi <br><br>};<br><br>{\mathrm{\theta <br><br>}}_m,{\mathrm{\theta <br><br>}}_r\right)=\frac{2<br><br>f<br><br>\text{\hspace{1em}<br><br>}<br><br>\cos <br><br>\left(\mathrm{\varphi <br><br>}-{\mathrm{\theta <br><br>}}_r\right)}{1-\cos <br><br>\left(\mathrm{\varphi <br><br>}+{\mathrm{\theta <br><br>}}_m\right)}-2<br><br>r_i<br><br>\sin <br><br>\left({\mathrm{\theta <br><br>}}_r\right)\end{array}$

wherein angle θ

_r is approximately one-half of angle θ

_m and wherein

f=r_i[1+sin(θ

_m)].

39. The method of claim 37 wherein the step of forming a plurality of light collecting structures comprises the step of extrusion molding.

40. The method of claim 37 wherein the step of forming a plurality of light collecting structures comprises the step of injection roll molding

41. The method of claim 37 wherein the step of forming a plurality of light collecting structures comprises the step of lamination.

42. The method of claim 38 wherein angle θ

_r is in the range from 10 to 30 degrees.