Optical film

Patent metadata

Field	Value
Publication number	US-9664834-B2
Application number	US-93548509-A
Country	US
Kind code	B2
Filing date	Mar 30, 2009
Priority date	Mar 31, 2008
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

An optical film that includes a reflective polarizer and a stretched polymer film is disclosed. The stretched polymer film is laminated to the reflective polarizer, and the stretched polymer film exhibits a refractive index symmetry point at an angle of incidence in air of at least about 60 degrees in a plane of incidence parallel to a direction of greatest stretch.

First claim

What is claimed is:

1. An optical film, comprising:
a reflective polarizer having a pass axis; and
a stretched polymer film having an x-axis in a direction of greatest stretch, a z-axis normal to a plane of the stretched polymer film, and a y-axis perpendicular to both the x-axis and the z-axis, wherein the stretched polymer film is laminated to the reflective polarizer;
wherein the stretched polymer film exhibits a refractive index symmetry point at an angle of incidence in air of at least about 60 degrees with respect to the z-axis in an x-z plane;
wherein an angle between the y-axis of the stretched polymer film and the pass axis of the reflective polarizer is less than about 10 degrees.

2. The optical film of claim 1 , wherein the stretched polymer film is monolithic.

3. The optical film of claim 1 , wherein the stretched polymer film comprises polyethylene terephthalate.

4. The optical film of claim 1 , further comprising an optical layer disposed proximate the stretched polymer film such that the stretched polymer film is between the optical layer and the reflective polarizer.

5. The optical film of claim 4 , wherein the optical layer is diffuse.

6. The optical film of claim 4 , wherein the optical layer comprises a plurality of refractive elements.

7. The optical film of claim 6 , wherein the plurality of refractive elements comprises beads.

8. The optical film of claim 6 , wherein the plurality of refractive elements comprises elongated prisms.

9. The optical film of claim 1 , wherein the stretched polymer film and the reflective polarizer are laminated with an adhesive.

10. An optical film, comprising:
a reflective polarizer having a pass axis; and
a stretched polymer film having an x-axis in a direction of greatest stretch, a z-axis normal to a plane of the stretched polymer film, and a y-axis perpendicular to both the x-axis and the z-axis, wherein the stretched polymer film is attached to the reflective polarizer;
wherein the stretched polymer film exhibits a refractive index symmetry point at an angle of incidence in air of at least about 60 degrees with respect to the z-axis in an x-z plane, and further wherein the stretched polymer film comprises a polymeric material not present in the reflective polarizer;
wherein an angle between the y-axis of the stretched polymer film and the pass axis of the reflective polarizer is less than about 10 degrees.

11. An optical film, comprising:
a reflective polarizer having first and second major surfaces;
a first stretched polymer film laminated with a first adhesive layer to the first major surface of the reflective polarizer;
a second stretched polymer film laminated with a second adhesive layer to the second major surface of the reflective polarizer; and
an optical layer disposed proximate the second stretched polymer film such that the second stretched polymer film is between the optical layer and the reflective polarizer;
wherein each of the first and second stretched polymer films exhibits a refractive index symmetry point at an angle of incidence in air of at least about 90 degrees.

12. A display system comprising a backlight, wherein the backlight comprises:
an illumination device;
a reflective polarizer having a pass axis; and
a stretched polymer film having an x-axis in a direction of greatest stretch, a z-axis normal to a plane of the stretched polymer film, and a y-axis perpendicular to both the x-axis and the z-axis, the stretched polymer film disposed such that the reflective polarizer is between the illumination device and the stretched polymer film;
wherein the stretched polymer film exhibits a refractive index symmetry point at an angle of incidence in air of at least about 60 degrees with respect to the z-axis in an x-z plane;
wherein an angle between the y-axis of the stretched polymer film and the pass axis of the reflective polarizer is less than about 10 degrees.

13. The display system of claim 12 , further comprising a dichroic polarizer, wherein the stretched polymer film is disposed between the reflective polarizer and the dichroic polarizer.

14. The display system of claim 12 , wherein an angle between the y-axis of the stretched polymer film and the pass axis of the reflective polarizer is less than about 10 degrees.

15. The display system of claim 12 , further comprising a liquid crystal panel positioned such that the stretched polymer film is between the illumination device and the liquid crystal panel.

16. A display system comprising a backlight, wherein the backlight comprises:
a polarized illumination device having a polarization axis; and
a stretched polymer film having an x-axis in a direction of greatest stretch, a z-axis normal to a plane of the stretched polymer film, and a y-axis perpendicular to both the x-axis and the z-axis, the stretched polymer film positioned to receive a polarized light from the polarized illumination device;
wherein the stretched polymer film exhibits a refractive index symmetry point at an angle of incidence in air of at least about 60 degrees with respect to the z-axis in an x-z plane.

17. The display system of claim 16 , wherein an angle between the y-axis of the stretched polymer film and the polarization axis of the polarized illumination device is less than about 10 degrees.

18. A display system comprising a backlight, wherein the backlight comprises:
an illumination device; and
a stretched polymer film;
wherein the stretched polymer film exhibits retardation of at least 3000 nm along all optical paths incident upon the stretched polymer film at an angle of incidence in air less than about 50 degrees.

19. A method of making an optical film comprising forming a stretched polymer film, wherein forming the stretched polymer film comprises:
forming a web of a polyethylene terephthalate;
stretching the web in a length direction by a first amount of about 1.05 to 1.3 times an unstretched length dimension;
stretching the web in a transverse direction by a second amount of about 3 to 7 times an unstretched transverse dimension;
heat-setting the web;
relaxing the web in the transverse direction; and
relaxing the web in an oven while unrestrained in the transverse direction and under minimal tension in the length direction.

20. The method of claim 19 , wherein the resulting stretched polymer film exhibits a refractive index symmetry point at an angle of incidence in air of at least about 90 degrees.

21. The method of claim 19 , wherein the resulting stretched polymer film exhibits retardation of at least 3000 nm along all optical paths incident upon the stretched polymer film at an angle of incidence in air less than about 50 degrees.

22. The method of claim 19 , further comprising disposing an optical layer on the stretched polymer film.

23. The method of claim 19 , further comprising attaching the stretched polymer film to a reflective polarizer.

Assignees

• Bösl Ellen R
• Chien Bert T
• Franke Carsten
• Hart Shandon D
• Hedding Brent A
• Karg Jr Donovan C
• Ludemann Thomas J
• Bradley Meghan A
• O'Neill Mark B
• Peterson Jeffrey A
• Strobel Joan M
• Tai Huiwen
• Van Derlofske Iii John F
• Weber Michael F
• Wong Chiu Ping
• Pokorny Richard J
• Baetzold John P
• 3M Innovative Properties Co

Inventors

• Bösl Ellen R
• Chien Bert T
• Franke Carsten
• Hart Shandon D
• Hedding Brent A
• Karg Jr Donovan C
• Ludemann Thomas J
• Bradley Meghan A
• O'Neill Mark B
• Peterson Jeffrey A
• Strobel Joan M
• Tai Huiwen
• Van Derlofske Iii John F
• Weber Michael F
• Wong Chiu Ping
• Pokorny Richard J
• Baetzold John P

Classifications

• G02F2001/133543

  Physics · mapped topic

• G02F2001/133531

  Physics · mapped topic

• G02F1/13362

  providing polarized light, e.g. by converting a polarisation component into another one · CPC title

• G02F2413/12

  Biaxial compensators · CPC title

• G02F1/133606 Primary

  including a specially adapted diffusing, scattering or light controlling members · CPC title