CURVED OPTICAL FILTERS

• US 20090097117A1
• Filed: 10/10/2008
• Published: 04/16/2009
• Est. Priority Date: 10/11/2007
• Status: Active Grant

• Current Assignee: RealD Incorporated
• Original Assignee: Real D
• Inventors: Coleman, David A.
• Granted Patent: US 8,687,275 B2
• Time in Patent Office: Days
• US Class Current: 359/489.19
• CPC Class Codes: B29D 11/00634 Production of filters
• CPC Class Codes: B29D 11/00644 polarizing
• CPC Class Codes: B29D 11/0073 Optical laminates
• CPC Class Codes: B29K 2995/0034 Polarising
• CPC Class Codes: B32B 2307/40 having particular optical properties
• CPC Class Codes: B32B 37/12 characterised by using adhesives
• CPC Class Codes: B32B 38/1866 conforming the layers or laminate to a convex or concave profile
• CPC Class Codes: G02B 30/25 using polarisation techniques
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor
• CPC Class Codes: Y10T 156/1007 Running or continuous length work
• CPC Class Codes: Y10T 156/1744 Means bringing discrete articles into assembled relationship

Abstract

Curved polarization filters and methods of manufacturing such filters are described in the present disclosure. An exemplary method includes laminating a planar polarization layer to a planar retarder layer at a predetermined orientation and bending the laminate to create a curved filter. The strain on the retarder layer results in stress-induced birefringence, and the predetermined orientation of the retarder substantially compensates for the stress-induced birefringence. In some embodiments, the predetermination is based on mathematical models. In some other embodiment, the predetermination is based on experimental data.

Claims

1. A method for manufacturing a curved filter having a retardation axis in a desired orientation, the method comprising:

providing a planar retarder film having an optical axis;

providing a planar polarization film;

predetermining an angle at which the planar retarder film would be laminated to the planar polarization film;

laminating the planar retarder film and the planar polarization film at the predetermined angle;

bending the laminated retarder and polarization films, whereby a stress is exerted on the retarder film, the stress causing a stress-induced birefringence in the retarder film; and

wherein the predetermined angle substantially compensates for the stress-induced birefringence and allow the optical axis of the retarder film to be in the desired orientation.

2. The method of claim 1, wherein the predetermined angle is determined using a mathematical model.

3. The method of claim 1, wherein the predetermined angle is determined using a chart or table, the chart or table providing a correlation between the radius of the curved filter to the predetermined angle.

4. The method of claim 1, wherein the planar retarder film comprises a quarter-wave plate.

5. The method of claim 1, wherein the planar retarder film comprises a multi-layer retarder stack.

6. The method of claim 1, wherein the planar retarder film is made of cyclic olefin block copolymer or cellulose di-acetate.

7. The method of claim 1, further comprising laminating a non-birefringent film to the planar retarder film, the planar retarder film being laminated between the non-birefringent film and the polarization film.

8. An optical filter in a curved configuration, the filter comprising:

a retarder layer and a polarization layer;

wherein the retarder and polarization layers are configured to have a compound curvature.

9. The filter of claim 8, wherein the retarder layer is made of a material whose strain optic coefficient is between 0.001 to 0.025.

10. The filter of claim 8, wherein the retarder layer has a thickness between 50 to 120 micron.

11. The filter of claim 8, wherein the optical filter was thermoformed.

12. An optical filter in a curved configuration, the filter comprising:

a polarization layer; and

a retarder layer laminated to the polarization layer at a predetermined angle, wherein the retarder and polarization layers are bent to the curved configuration,

wherein the retarder layer has a stress-induced birefringence, and further wherein the predetermined angle substantially compensates for the stress-induced birefringence and disposes the optical axis of the retarder film in a desired orientation.

13. The filter of claim 12, wherein an outer surface of the polarizer layer is laminated to an inner surface of the retarder layer.

14. The filter of claim 13, further comprising a non-birefringent layer laminated to an outer surface of the retarder layer, the non-birefringent layer being operable to compensate the stress birefringence in the retarder layer.

15. The filter of claim 12, wherein an outer surface of the retarder layer is laminated to an inner surface of the polarizer layer.

16. The filter of claim 15, further comprising a non-birefringent layer laminated to an inner surface of the retarder layer, the non-birefringent layer being operable to compensate the stress birefringence in the retarder layer.

17. The filter of claim 12, wherein the polarizer and retarder layers are laminated with a pressure sensitive adhesive.

18. The filter of claim 12, wherein the retarder layer comprises a multi-layer retarder stack.

19. The filter of claim 12, wherein the retarder layer comprises a quarter wave plate.

20. The filter of claim 12, wherein the planar retarder film is made of cyclic olefin block copolymer or cellulose di-acetate.

21. A method for manufacturing a curved optical filter, the method comprising:

providing a drum having a curved surface;

feeding a first optical film onto the curved surface of the drum at a first rate;

feeding a second optical film onto an outer surface of the first film at a second rate;

coating the outer surface of the first film or an inner surface of the second film with an adhesive;

rotating the drum as the first and second films are being fed; and

laminating the first and second films together using a press roller.

22. The method of claim 21, wherein the first and second films are fed into the drum at different angles.

23. The method of claim 21, wherein the drum and an inner surface of the curved filter have the same curvature.

24. The method of claim 21, wherein the first film is a polarizer.

25. The method of claim 21, wherein the first film is a retarder.

26. The method of claim 21, wherein the first film is a polarizer and the second film is a retarder.

27. The method of claim 21, wherein the adhesive is a pressure-sensitive adhesive.

28. The method of claim 21, wherein the second rate is faster than the first rate.

29. An apparatus for laminating curved optical films, comprising:

a curved drum operable to provide a curved surface for bonding first and second optical films;

at least two feeders operable to feed the first and second optical films onto the curve drum;

a coating apparatus operable to apply adhesive to a surface of the first or second optical film; and

a press roller operable to apply pressure against the first and second optical films and laminate the first and second optical films.