Reflective polarizer with polarization splitting microstructure

• US 7,646,453 B2
• Filed: 12/21/2006
• Issued: 01/12/2010
• Est. Priority Date: 06/05/2006
• Status: Active Grant

• Current Assignee: SKC Hi-Tech & Marketing Co., Ltd.
• Original Assignee: SKC Haas Display Films Co., Ltd. (Dow, Inc.)
• Inventors: Kowarz, Marek W., Greener, Jehuda, Anderson, Charles C.
• Primary Examiner(s): Wood; Kevin S
• Application Number:
  US11/643,093
• Publication Number:
  US 20070279554A1
• Time in Patent Office: 1,118 Days
• Field of Search: 349 96-103
• US Class Current: 349/96
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 5/3066 involving the reflection of light at a particular angle of incidence, e.g. Brewster's angle
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one

Abstract

A reflective polarizer contains:

• • (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.

Claims

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.