Optical film for back light unit and back light unit including same

1. An optical film for a back light unit comprising an array of light emitting diodes, the optical film comprising:

a substrate; and

a plurality of regions of spatially modulated microstructures on at least one side of the substrate, wherein at least one of the plurality of regions is positioned directly over a light emitting diode comprising the array of light emitting diodes, the gradient structure within each region being constructed and arranged to cause a first level of spreading of light when positioned directly above an individual light emitting diode and a second level of spreading of light at locations not directly above an individual light emitting diode, the second level being less that the first level, the plurality of regions of spatially modulated microstructures on at least one side of the substrate comprising a plurality of first regions constructed and arranged to cause the first level of spreading of light, and each of the plurality of first regions comprises a first plurality of parallel prisms oriented in a first direction on a first side of the substrate and a second plurality of parallel prisms oriented in a second direction orthogonal to the first direction on a second side of the substrate opposite the first side,

the plurality of regions of spatially modulated microstructures on at least one side of the substrate further comprising a plurality of second regions constructed and arranged to cause the second level of spreading of light, and each of the plurality of second regions comprises the first plurality of parallel prisms oriented in the first direction on the first side of the substrate and a third plurality of parallel prisms oriented in the first direction on the second side of the substrate,

the plurality of regions of spatially modulated microstructures on at least one side of the substrate further comprising a plurality of third regions that surround outer perimeters of the plurality of first regions, and each of the plurality of third regions is constructed and arranged to cause a third level of spreading of light, the third level being less than the first level and greater than the second level, and each of the plurality of third regions comprises a gradient comprising a fourth plurality of elongated prisms on the second side of the substrate continuously varying in angle relative to the first direction and the second direction as the positions of the fourth plurality of elongated prisms move away from the first regions so as to create a swirl-like pattern that surrounds the second plurality of elongated prisms in the first regions on the second side of the substrate.

2. The optical film according to claim 1 , wherein the spatially modulated microstructures comprise a plurality of elongated prisms.

3. The optical film according to claim 1 , wherein the spatially modulated microstructures comprise a plurality of three-sided pyramids.

4. The optical film according to claim 1 , wherein the spatially modulated microstructures comprise a plurality of cones.

5. The optical film according to claim 1 , wherein the first plurality of parallel prisms and the second plurality of parallel prisms have apexes having substantially the same angles.

6. The optical film according to claim 5 , wherein the angles are about 90°.

7. The optical film according to claim 1 , wherein a plurality of third regions is constructed and arranged to cause a third level of spreading of light, the third level being less than the first level and greater than the second level, and each of the plurality of third regions comprises a gradient comprising a mixture of the second plurality of prisms and the third plurality of prisms on the second side of the substrate.

8. A back light unit comprising:

an array of light emitting diodes; and

an optical film positioned above the array of light emitting diodes, the optical film comprising

a substrate, and

a plurality of regions of spatially modulated microstructures on at least one side of the substrate, each of the plurality of regions positioned over a respective light emitting diode, wherein at least one of the plurality of regions is positioned directly over a light emitting diode comprising the array of light emitting diodes, the gradient structure within each region being constructed and arranged to convert light beams emitted by the respective light emitting diode at different angles into a more uniform and higher on-axis luminance upon exiting the back light unit,

the plurality of regions of spatially modulated microstructures on at least one side of the substrate comprising a plurality of first regions constructed and arranged to cause the first level of spreading of light, and each of the plurality of first regions comprises a first plurality of parallel prisms oriented in a first direction on a first side of the substrate and a second plurality of parallel prisms oriented in a second direction orthogonal to the first direction on a second side of the substrate opposite the first side, and wherein centers of the plurality of first regions are positioned directly over centers of the light emitting diodes,

the plurality of regions of spatially modulated microstructures on at least one side of the substrate further comprising a plurality of second regions constructed and arranged to cause the second level of spreading of light, and each of the plurality of second regions comprises the first plurality of parallel prisms oriented in the first direction on the first side of the substrate and a third plurality of parallel prisms oriented in the first direction on the second side of the substrate, and wherein centers of the plurality of second regions are positioned directly over areas between the light emitting diodes,

the plurality of regions of spatially modulated microstructures on at least one side of the substrate further comprising a plurality of third regions that surround outer perimeters of the plurality of first regions, and each of the plurality of third regions constructed and arranged to cause a third level of spreading of light, the third level being less than the first level and greater than the second level, and each of the plurality of third regions comprises a gradient comprising a fourth plurality of elongated prisms on the second side of the substrate continuously varying in angle relative to the first direction and the second direction as the positions of the fourth plurality of elongated prisms move away from the first regions so as to create a swirl-like pattern that surrounds the second plurality of elongated prisms in the first regions on the second side of the substrate.

9. The back light unit according to claim 8 , wherein centers of the regions are positioned directly over centers of the light emitting diodes.

10. The back light unit according to claim 8 , wherein the spatially modulated microstructures comprise a plurality of elongated prisms.

11. The back light unit according to claim 8 , wherein the spatially modulated microstructures comprise a plurality of three-sided pyramids.

12. The back light unit according to claim 8 , wherein the spatially modulated microstructures comprise a plurality of cones.

13. The back light unit according to claim 8 , wherein the first plurality of parallel prisms and the second plurality of parallel prisms have apexes having substantially the same angles.

14. The back light unit according to claim 13 , wherein the angles are about 90°.

15. The back light unit according to claim 8 , wherein a plurality of third regions is constructed and arranged to cause a third level of spreading of light, the third level being less than the first level and greater than the second level, and each of the third plurality of regions comprises a gradient comprising a mixture of the second plurality of prisms and the third plurality of prisms on the second side of the substrate.