Light directing film and method for making the same

Patent metadata

Field	Value
Publication number	US-9810817-B2
Application number	US-93485509-A
Country	US
Kind code	B2
Filing date	Apr 1, 2009
Priority date	Apr 2, 2008
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

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.

First claim

The invention claimed is:

1. A light directing film comprising a structured major surface, wherein the structured major surface comprises a plurality of microstructures, wherein at least a portion of the microstructures are linear and extend along a first direction, and wherein each microstructure comprises:
first regions with a constant height along a second direction normal to the first direction and a first apex having first dihedral angle α 1 , and
second regions adjacent to the first regions, wherein the second regions have a non-constant height along the second direction and a maximum height greater than the constant height of the first regions and a second apex having a second dihedral angle α 2 the same as α 1 , and wherein the second regions extend outwardly along a third direction normal to the first and the second directions such that the first regions and the second regions have the same lateral cross sectional shape; and
wherein the second regions are arranged on the structured major surface such that at least one of: (1) the average density of the second regions on the structured major surface, (2) the average period of the second regions on the structured major surface, and (3) the height of the second regions relative to the height of the first regions, are sufficient to control the physical proximity of a second major surface to the structured major surface such that the second major surface contacts the second regions on the structured major surface and optical coupling between the structured major surface and the second major surface occurs primarily within the second regions.

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 distributions are periodic.

6. The light directing film of claim 4 , wherein the regular distributions are 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 the microstructures are linear and extend continuously along the first direction.

10. The light directing film of claim 9 , wherein the microstructures are adjacent one another.

11. The light directing film of claim 9 , wherein the microstructures have a triangular cross sectional shape.

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

13. The light directing film of claim 9 , wherein the maximum height in the second regions is about 0.5 μm to about 3 μm greater than the constant height.

14. The light directing film of claim 9 , wherein a density of the second regions is from about 200 to about 6000 per cm 2 of the structured surface.

15. The light directing film of claim 9 , wherein a period of the second regions is about 1000 to about 20,000 μm.

16. The light directing film of claim 9 , wherein the second regions have an average height of about 1 μm to about 2.5 μm and a density of about 200 to about 3500 per cm 2 of the structured surface.

17. The light directing film of claim 9 , wherein the second regions have an average height of about 1.5 μm to about 2.0 μm and a density of about 200 to about 2500 per cm 2 of the structured surface.

18. The light directing film of claim 8 , wherein the microstructures have a triangular cross sectional shape and a dihedral angle of about 70° to about 110°.

19. The light directing film of claim 8 , wherein the microstructures have a triangular cross sectional shape and the constant height of the first regions is about 1 μm to about 200 μm.

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

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

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

23. The light directing film of claim 22 , wherein the maximum height of the second regions varies regularly.

24. The light directing film of claim 22 , wherein the maximum height of the second regions varies randomly.

25. 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.

26. The light directing film of claim 25 , wherein the second major surface comprises structures.

27. 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 linear microstructures extending along a first direction, and wherein each microstructure comprises:
a first region having a first apex having first dihedral angle α 1 , and
a second region having a second apex having a second dihedral angle α 2 the same as α 1 , wherein the second region is different from and adjacent to the first region, and wherein a microstructure has a substantially constant height along a second direction normal to the first direction in the first region and non-constant height along the second direction in the second region with a maximum height about 0.5 to about 3 microns greater than the substantially constant height in the first region, and wherein the second region extends outwardly along a third direction normal to the first and the second directions such that the first region and the second region have a 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 direction approximately perpendicular to the first direction; and

wherein the second regions of the structured surface of the first light directing film are arranged such that at least one of: (1) the average density of the second regions on the structured major surface of the first sheet of light directing film, (2) the average period of the second regions on the structured major surface of the first sheet of the light directing film, and (3) the height of the second regions relative to the height of the first regions, are sufficient to cause optical coupling between the first and second sheets of light directing film to occur predominately in the second regions on the structured major surface of the first sheet of the light directing film.

28. An optical display, comprising
a light source;
a viewing screen

Assignees

• Campbell Alan B
• Ehnes Dale L
• Van Derlofske Iii John F
• Dupre Mark R
• Dreyer Stephen J
• Marushin Patrick H
• Johnson Todd M
• Hunt Bryan V
• 3M Innovative Properties Co

Inventors

• Campbell Alan B
• Ehnes Dale L
• Van Derlofske Iii John F
• Dupre Mark R
• Dreyer Stephen J
• Marushin Patrick H
• Johnson Todd M
• Hunt Bryan V

Classifications

• G02B6/0053 Primary

  Prismatic sheet or layer; Brightness enhancement element, sheet or layer · CPC title

• G02F2001/133607

  Physics · mapped topic

• G02B5/045 Primary

  Prism arrays · CPC title

• G02F1/133615

  Edge-illuminating devices, i.e. illuminating from the side · CPC title

• G02F1/133607

  the light controlling member including light directing or refracting elements, e.g. prisms or lenses · CPC title