LIGHT DIRECTING FILM AND METHOD FOR MAKING THE SAME

• US 20110199697A1
• Filed: 04/01/2009
• Published: 08/18/2011
• Est. Priority Date: 04/02/2008
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Campbell, Alan B., Dreyer, Stephen J., Johnson, Todd M., Marushin, Patrick H., Hunt, Bryan V., Dupre, Mark R., Ehnes, Dale L., Van Derlofske, John F. III
• Granted Patent: US 9,810,817 B2
• Time in Patent Office: Days
• US Class Current: 359/831
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

A light directing film includes a structured major surface with a plurality of microstructures extending along a first direction. Each microstructure has a first region and a second region different from the first region, a substantially constant height in the first region and a non-constant maximum height in the second region greater than the substantially constant height in the first region, and a same lateral cross sectional shape in the first region and the second region.

Claims

1. A light directing film comprising a structured major surface, wherein the structured major surface comprises a plurality of microstructures extending along a first direction, and wherein a microstructure comprises:

a first region with a constant height, and

a second region adjacent to the first region, wherein the second region has a non-constant height and a maximum height greater than the constant height of the first region, and wherein the first region and the second region have the same lateral cross sectional shape.

2. The light directing film of claim 1, wherein each microstructure comprises a plurality of first and second regions, and wherein the second regions are discontiguous.

3. The light directing film of claim 2, wherein the second regions are distributed randomly on the microstructures on the major surface of the film.

4. The light directing film of claim 2, wherein the second regions are distributed regularly on the microstructures on the major surface of the film.

5. The light directing film of claim 4, wherein the regular pattern is periodic.

6. The light directing film of claim 4, wherein the regular pattern is aperiodic.

7. The light directing film of claim 2, wherein the second regions are distributed semi-randomly on the microstructures on the major surface of the film.

8. The light directing film of claim 3, wherein the microstructures comprise a cross sectional shape selected from at least one of triangular, circular, lenticular, elliptical, conical, or having a curved portion.

9. The light directing film of claim 8, wherein at least a portion of the microstructures are linear and extend along the first direction.

10. The light directing film of claim 8, wherein the microstructures are linear and extend continuously along the first direction.

11. The light directing film of claim 10, wherein the microstructures are adjacent one another.

12. The light directing film of claim 10, wherein the microstructures have a triangular cross sectional shape.

13. The light directing film of claim 11, wherein the microstructures have a triangular cross sectional shape.

14. The light directing film of claim 10, wherein the maximum height in the second regions is about 0.5 μ

m to about 3 μ

m greater than the constant height

15. The light directing film of claim 10, wherein the density of the second regions is from about 200 to about 6000 per cm² of the structured surface.

16. The light directing film of claim 10, wherein the period of the second regions is about 1000 to about 20,000.

17. The light directing film of claim 10, wherein the second regions have an average height of about 1 μ

m to about 2.5 μ

m and a density of about 200 to about 3500 per cm² of the structured surface.

18. The light directing film of claim 10, wherein the second regions have an average height of about 1.5 μ

m to about 2.0 μ

m and a density of about 200 to about 2500 per cm² of the structured surface.

19. The light directing film of claim 8, wherein the prisms have a triangular cross sectional shape and a dihedral angle of about 70°

to about 110°

.

20. The light directing film of claim 8, wherein the prisms have a triangular cross sectional shape and the substantially constant height of the first regions is about 1 μ

m to about 200 μ

m.

21. The light directing film of claim 8, wherein the cross-sectional shape of the prisms is asymmetric.

22. The light directing film of claim 8, wherein at least two second regions have the same maximum height.

23. The light directing film of claim 8, wherein at least two second regions have different maximum heights.

24. The light directing film of claim 23, wherein the maximum height of the second regions varies regularly.

25. The light directing film of claim 23, wherein the maximum height of the second regions varies randomly.

26. The light directing film of claim 1, wherein the film comprises a second major surface opposite the structured surface, and wherein the second major surface is substantially smooth.

27. The light directing film of claim 26, wherein the second major surface comprises structures.

28. A light directing article comprising

a first sheet of light directing film comprising a structured major surface, wherein the structured major surface comprises a plurality of microstructures extending along a first direction, and wherein a microstructure comprises:

a first region and a second region, wherein the second region is different from and adjacent to the first region, and wherein a microstructure has a substantially constant height in the first region and a maximum, non-constant height in the second region about 0.5 to about 3 microns greater than the constant height in the first region, and wherein the first region and the second region have the same lateral cross sectional shape; and

a second sheet of light directing film having a substantially planar surface and a structured surface opposite the substantially planar surface, wherein the substantially planar surface is adjacent the structured surface of the first sheet of light directing film, and wherein the structured surface of the second sheet of light directing film comprises a plurality of microstructures extending along a second major axis approximately perpendicular to the first major axis; and

wherein any optical coupling between the first and second sheets occurs predominately in the second regions.

29. An optical display, comprising

a light source;

a viewing screen; and

a light directing film that directs light from the light source to the viewing screen, wherein the light directing film has

a first major surface; and

a structured second major surface comprising a plurality of microstructures, wherein a microstructure has a repeating pattern that comprises a first region and an adjacent second region, wherein;

the first region has a constant height; and

the second region has a non-constant, maximum height greater than the constant height of the first region, wherein the maximum height of the second regions is about 0.5 μ

m to about 3 μ

m greater than the constant height of the first regions, and wherein the repeating pattern has a density of at least 200 second regions per cm²; and

wherein the first region and the second region have a same lateral cross sectional shape.

30. The optical display of claim 29, wherein the peaks of the microstructures face toward the viewing screen.

31. The optical display of claim 29, wherein the peaks of the microstructures face away from the viewing screen.

32. A method of making a light directing film, comprising:

cutting a tool with a structured major surface, wherein the structured major surface comprises a plurality of grooves extending along a first direction, wherein a groove comprises;

a first region and a second region, wherein the second region is different from and adjacent to the first region, and

a constant height in the first region and a maximum height in the second region greater than the substantially constant height in the first region, wherein the first region and the second region have the same lateral cross sectional shape; and

applying a polymeric material to the tool to form a film, wherein the film comprises an arrangement of microstructures corresponding to the grooves in the tool.

33. A method of reducing wet out in a display device, comprising incorporating into the device a light directing film, wherein the light directing film comprises a structured major surface, wherein the structured major surface comprises a plurality of microstructures extending along a first direction, and wherein a microstructure comprises:

a first region and a second region, wherein the second region is different from and adjacent to the first region, and

a substantially constant height in the first region and a maximum height in the second region greater than the substantially constant height in the first region, wherein the first region and the second region have the same lateral cross sectional shape.