Method of making optical films and stacks
Methods of making optical films and optical stacks are described. A method of making an optical stack includes providing a thermoform tool centered on a tool axis and having an external surface rotationally asymmetric about the tool axis; heating an optical film resulting in a softened optical film; conforming the softened optical film to the external surface while stretching the softened film along at least orthogonal first and second directions away from the tool axis resulting in a conformed optical film rotationally asymmetric about an optical axis of the conformed film where the optical axis coincident with the tool axis; cooling the conformed optical film resulting in a symmetric optical film rotationally symmetric about the optical axis; and molding an optical lens on the symmetric optical film resulting in the optical stack.
1. A method of making an optical stack comprising a desired optical film having a desired shape, the method comprising:
providing a tool having an external surface having a first shape different than the desired shape;
conforming the optical film to the external surface having the first shape while stretching the optical film along at least orthogonal first and second directions resulting in a conformed optical film having the first shape;
releasing the conformed optical film from the external surface resulting in the desired optical film having the desired shape; and
molding an optical lens on the optical film resulting in the optical stack.
2. The method of making an optical stack of claim 1 , wherein the molding step comprises film insert molding.
3. The method of making an optical stack of claim 1 , wherein the molding step comprises injection molding.
4. The method of claim 1 , wherein the molding step comprises molding a second film on the optical lens opposite the desired optical film.
5. The method of claim 4 , wherein the second film comprises a partial reflector.
6. The method of claim 5 , wherein the second film further comprises a quarter wave retarder.
7. The method of claim 5 , wherein the desired optical film comprises a reflective polarizer.
8. The method of claim 7 , wherein the desired optical film further comprises a quarter wave retarder.
9. The method of claim 7 , wherein the reflective polarizer is a multilayer polymeric reflective polarizer.
10. The method of claim 9 , wherein the reflective polarizer has at least one substantially uniaxially oriented layer.
11. The method of claim 7 , wherein the reflective polarizer is a wire grid polarizer.
12. The method of claim 1 , wherein the desired optical film comprises a reflective polarizer.
13. The method of claim 12 , wherein the desired optical film further comprises a quarter wave retarder.
14. The method of claim 12 , wherein the reflective polarizer is a multilayer polymeric reflective polarizer.
15. The method of claim 14 , wherein the reflective polarizer has at least one substantially uniaxially oriented layer.
16. The method of claim 12 , wherein the reflective polarizer is a wire grid polarizer.
17. The method of claim 1 , wherein the first shape is a shape of a portion of an ellipsoid.
18. The method of claim 1 , wherein conforming the optical film to the external surface comprises heating the optical film.
19. The method of claim 18 , wherein the releasing step further comprises cooling the conformed optical film.
20. The method of claim 1 , wherein conforming the optical film to the external surface comprises softening the optical film.