Reflective polarizer with polarization splitting microstructure

1. A reflective polarizer for an LCD backlight unit comprising:

(a) a light-entrance medium having a light-entrance surface and a microstructured surface with a series of prismatic structures, wherein first and second sidewalls of each prismatic structure have an inclination angle of more than 53 degrees with respect to the light-entrance surface;

(b) a polarization-selective thin film optical coating on the series of prismatic structures, for transmitting a first polarization of light and reflecting a second polarization; and

(c) a light-exit medium on the polarization-selective thin film optical coating that provides a smooth light-exit surface for outputting light from the LCD backlight unit.

2. The reflective polarizer of claim 1 , wherein the second polarization of light undergoes three or more reflections before exiting the reflective polarizer film.

3. The reflective polarizer of claim 1 , wherein the second polarization of light undergoes total internal reflection at the smooth light-exit surface.

4. The reflective polarizer of claim 1 , wherein the inclination angle is not more than 70 degrees.

5. The reflective polarizer of claim 1 , wherein the inclination angle is between 60 and 70 degrees.

6. The reflective polarizer of claim 1 wherein standoffs are provided on the light-exit surface of the polarizer to provide an air gap between the polarizer and a surface adjacent to the light-exit surface.

7. The reflective polarizer of claim 1 wherein the first polarization is p-polarization.

8. The reflective polarizer of claim 1 wherein either the light-entrance medium or the light-exit medium comprise an epoxy.

9. The reflective polarizer of claim 8 further comprising a smoothing sheet on the epoxy.

10. The reflective polarizer of claim 1 wherein the polarization-selective thin film optical coating comprises 10 or fewer layers.

11. A method for fabricating a reflective polarizer for an LCD backlight unit comprising the steps of:

(a) providing a prism substrate having a first smooth surface and a microstructured surface with a series of prismatic structures, wherein first and second sidewalls of each prismatic structure have an inclination angle of more than 53 degrees with respect to the light-entrance surface;

(b) depositing a polarization-selective thin film optical coating on the series of prismatic structures, for transmitting a first polarization of light and reflecting a second polarization;

(c) applying an epoxy on top of the polarization-selective thin film optical coating; and

(d) forming a second smooth surface on the epoxy by attaching a flat smoothing sheet for outputting light from the LCD backlight unit.

12. A method for fabricating a reflective polarizer for an LCD backlight unit comprising the steps of:

(a) providing a prism substrate having a first smooth surface and a microstructured surface with a series of prismatic structures, wherein first and second sidewalls of each prismatic structure have an inclination angle of more than 53 degrees with respect to the light-entrance surface;

(b) depositing a polarization-selective thin film optical coating on the series of prismatic structures, for transmitting a first polarization of light and reflecting a second polarization;

(c) applying an epoxy on top of the polarization-selective thin film optical coating; and

(d) forming a second smooth surface on the epoxy for outputting light from the LCD backlight unit.