TENSIONED OPTICAL ELEMENT AND DISPLAY
An optical element comprises at least one optical film wherein at least a portion of the optical film is maintained dimensionally stable by the presence of a mechanism for application of a controlled tensile force via an elastic material bonded to the perimeter of the film.
1 . An optical element comprising at least one optical film wherein at least a portion of the optical film is maintained dimensionally stable by the presence of a mechanism for application of a controlled tensile force to the film wherein the tensile force is applied through a tensioning mechanism comprising an elastic material bonded to the perimeter of the film.
2 . The optical element of claim 1 comprising an optical diffuser film.
3 . The optical element of claim 2 wherein the optical diffuser film comprises voids.
4 . The optical element of claim 1 wherein the tensile force is applied by mechanisms at various locations around the perimeter of the optical film.
5 . The optical element of claim 4 wherein the tensile force is applied in a direction perpendicular to the edge of the film nearest the applied location.
6 . The optical element of claim 1 wherein the tensile force can be substantially maintained for each mechanism over the expected film dimensional change for the design temperature and humidity range of the optical element.
7 . The optical element of claim 6 wherein the maximum change in applied tensile force for each mechanism is less than 50% of the highest force over the expected film dimensional change for the design temperature and humidity range of the optical element.
8 . The optical element of claim 6 wherein the maximum change in applied tensile force is less than 25% of the highest force over the expected film dimensional change for the design temperature and humidity range of the optical element.
9 . The optical element of claim 1 wherein the mechanism includes a supporting frame around the perimeter of the at least one optical film.
10 . The optical element of claim 9 wherein the elastic material connects the at least one optical film to the frame.
11 . The optical element of claim 1 comprising an optical diffuser film and a light directing film.
12 . The optical element of claim 11 further comprising a bead coated collimating diffuser film.
13 . A display comprising a light source and an optical element comprising an optical film, wherein at least a portion of the optical film is maintained dimensionally stable by the presence of a mechanism comprising elastic material bonded to the perimeter of the film for application of a controlled tensile force to the film.
14 . The display of claim 13 wherein the optical element comprises an optical diffuser film.
15 . A process for controlling the planar uniformity of an optical film comprising subjecting at least a portion of the film to a controlled tensile force via an elastic material bonded to the perimeter of the film.
16 . An optical element comprising at least one optical film wherein at least a portion of the optical film is maintained dimensionally stable by the presence of a mechanism for application of a controlled tensile force via an elastic material bonded to the perimeter of the film wherein the optical film is a diffuser film that contains voids.
17 . An optical element comprising at least one optical film wherein at least a portion of the optical film is maintained dimensionally stable by the presence of a mechanism for application of a controlled tensile force via an elastic material bonded to the perimeter of the film wherein the maximum change in applied tensile force for each mechanism is less than 50% of the highest force over the expected film dimensional change for the design temperature and humidity range of the optical element.
18 . The optical element of claim 1 where in the tensile force is applied through a frame that is part of a backlight unit.
19 . The optical element of claim 1 wherein a portion of two optical films are maintained dimensionally stable by the presence of a mechanism for application of a controlled tensile force via an elastic material bonded to the perimeter of the film.
20 . The optical element of claim 19 wherein at least 1 additional film is placed between the two optical films that are maintained dimensionally stable by the presence of a mechanism for application of a controlled tensile force via an elastic material bonded to the perimeter of the film.
21 . The optical element of claim 20 wherein the at least 1 additional film is restrained normal to the film surface by the two optical films that are maintained dimensionally stable by the presence of a mechanism for application of a controlled tensile force.
22 . The optical film of claim 21 wherein the at least 1 additional film is further restrained from translation and rotation in the plane of the film by a hole and slot in the film which are applied over pins.
23 . The optical element of claim 1 wherein the elastic material comprises an elastomer.
24 . The optical element of claim 23 wherein the elastomer comprises Polyurethanes, Silicone rubbers, Polychloroprene, Ethylene-propylene copolymer, Ethylene-propylene terpolymer, Vinylidene fluoride-chloro-trifluoro ethylene random copolymer, Vinylidene fluoride-chloro-hexa fluoro ethylene random copolymer, and High-Strength Buna-N Rubber.
25 . The optical element of claim 24 wherein the elastomer further comprises stabilizers or environmental protective agents.