HOLLOW BACKLIGHT WITH STRUCTURED FILMS

• US 20110051047A1
• Filed: 02/06/2009
• Published: 03/03/2011
• Est. Priority Date: 02/07/2008
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Freier, David G., Lamb, David J., Hart, Shandon D., O'Neill, Mark B., Epstein, Kenneth A.
• Granted Patent: US 8,848,132 B2
• Time in Patent Office: Days
• US Class Current: 349/67
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0096 the lights guides being of the hollow type

Abstract

A backlight (120) that includes a front reflector (130) and a back reflector (160) that form a hollow light recycling cavity (162) having an output surface (164) is disclosed. The front reflector includes at least four directional recycling films (132). The backlight also includes a semi-specular diffuser disposed between the front reflector and the back reflector, and one or more light sources (166) disposed to emit light into the light recycling cavity.

Claims

1. A backlight, comprising:

a front reflector and a back reflector that form a hollow light recycling cavity having an output surface, the front reflector comprising;

a first directional recycling film comprising an array of prisms elongated along a first axis; and

a second directional recycling film disposed such that the first directional recycling film is between the second directional recycling film and the back reflector, the second directional recycling film comprising an array of prisms elongated along a second axis;

a semi-specular diffuser disposed between the front reflector and the back reflector; and

one or more light sources disposed to emit light into the light recycling cavity over a limited angular distribution related to an emission axis;

wherein the first axis is substantially parallel to the emission axis.

2. The backlight of claim 1, wherein the second axis is substantially perpendicular to the first axis.

3. The backlight of claim 1 wherein the second axis is substantially parallel to the first axis.

4. The backlight of claim 1, wherein the front reflector further comprises a third directional recycling film disposed such that the second directional recycling film is between the third directional recycling film and the first directional recycling film.

5. The backlight of claim 4, wherein the third directional recycling film comprises an array of prisms elongated along a third axis.

6. The backlight of claim 5, wherein the first, second and third axes are substantially parallel.

7. The backlight of claim 4, wherein the front reflector further comprises a fourth directional recycling film disposed such that the third directional recycling film is between the fourth directional recycling film and the second directional recycling film.

8. The backlight of claim 7, wherein the front reflector further comprises a fifth directional recycling film disposed such that the fourth directional recycling film is between the fifth directional recycling film and the third directional recycling film.

9. The backlight of claim 1, wherein the semi-specular diffuser is disposed on the back reflector.

10. The backlight of claim 1, wherein the semi-specular diffuser is disposed on the first directional recycling film.

11. The backlight of claim 1, wherein the backlight exhibits a VESA 9 uniformity value of at least 50%.

12. The backlight of claim 1, wherein the output region is generally rectangular and has a diagonal measure of at least 30 mm.

13. The backlight of claim 1, wherein the front reflector has a hemispherical reflectivity for unpolarized visible light of R^f_hemi, and the back reflector has a hemispherical reflectivity for unpolarized visible light of R^b_hemi, and R^f_hemi*R^b_hemi is at least 0.70.

14. A backlight, comprising:

a front reflector and a back reflector that form a hollow light recycling cavity having an output surface, the front reflector comprising at least four directional recycling films;

a semi-specular diffuser disposed between the front reflector and the back reflector; and

one or more light sources disposed to emit light into the light recycling cavity.

15. The backlight of claim 14, wherein the at least four directional recycling films comprise:

three prismatic recycling films each comprising an array of prisms elongated along an axis; and

a gain diffuser film;

wherein the axes of the three prismatic recycling films are substantially parallel, and further wherein the three prismatic recycling films are disposed between the gain diffuser film and the back reflector.

16. The backlight of claim 14, wherein the at least four directional recycling films comprise five directional recycling films comprising:

two prismatic recycling films each comprising an array of prisms elongated along an axis; and

three gain diffuser films;

wherein the axes of the two prismatic recycling films are substantially perpendicular, and further wherein the two prismatic recycling films are disposed such that both prismatic recycling films are between the three gain diffuser films and the back reflector.

17. The backlight of claim 14, wherein the at least four directional recycling films comprise five directional recycling films comprising:

two prismatic recycling films each comprising an array of prisms elongated along an axis; and

three gain diffuser films;

wherein the axes of the two prismatic recycling films are substantially parallel, and further wherein the two prismatic recycling films are disposed such that both prismatic recycling films are between the three gain diffuser films and the back reflector.

18. The backlight of claim 14, wherein the at least four directional recycling films comprise six gain diffuser films.

19. The backlight of claim 14, wherein the front reflector further comprises a reflective polarizer.

20. A display comprising a liquid crystal panel and a backlight that provides light to the liquid crystal panel, wherein the backlight comprises:

a front reflector and a back reflector that form a hollow light recycling cavity having an output surface, the front reflector comprising;

a first directional recycling film comprising an array of prisms elongated along a first axis; and

a second directional recycling film disposed such that the first directional recycling film is between the second directional recycling film and the back reflector, the second directional recycling film comprising an array of prisms elongated along a second axis;

a semi-specular diffuser disposed between the front reflector and the back reflector; and

one or more light sources disposed to emit light into the light recycling cavity over a limited angular distribution related to an emission axis;

wherein the first axis is substantially parallel to the emission axis.

21. A display comprising a liquid crystal panel and a backlight that provides light to the liquid crystal panel, wherein the backlight comprises:

a front reflector and a back reflector that form a hollow light recycling cavity having an output surface, the front reflector comprising at least four directional recycling films;

a semi-specular diffuser disposed between the front reflector and the back reflector; and

one or more light sources disposed to emit light into the light recycling cavity.