Luminance enhancement structure for reflective display devices

1. A reflective display assembly comprising:

(a) a display device comprising display cells and a top substrate layer on the viewing side of the display device;

(b) a luminance enhancement structure on top of the display device on the viewing side of the display device, said luminance enhancement structure comprises

i) a top surface,

ii) grooves and columns, wherein each of said grooves has a triangular cross-section with a tilted surface, a top point and a top angle, and said grooves and columns are in alternating order and in continuous form only in one direction; and

(c) color filters,

whereby an incoming light from a light source on the viewing side of the display device transmits through the luminance enhancement structure, strikes the display device, and the light reflected from the display device and the tilted surface of the grooves reaches the top surface of the luminance enhancement structure.

2. The display assembly of claim 1 , wherein the top angles of the grooves are substantially equal.

3. The display assembly of claim 1 , wherein each of said columns has a top surface which is in optical contact with said top substrate layer.

4. The display assembly of claim 3 , wherein said top substrate layer has a thickness in the range of about 1 μm to about 175 μm.

5. The display assembly of claim 4 , wherein said top substrate layer has a thickness in the range of about 1 μm to about 25 μm.

6. The display assembly of claim 2 , wherein said top angle is in the range of about 5° to about 50°.

7. The display assembly of claim 6 , wherein said top angle is in the range of about 20° to about 40°.

8. The display assembly of claim 1 , wherein the titled surface of the grooves is uncoated.

9. The display assembly of claim 1 , wherein said luminance enhancement structure comprises an angle β which is smaller than a critical angle at the boundary between the top surface of the luminance enhancement structure and air, wherein said angle β is an angle formed at the intersection of (i) a line connecting the top point of a first groove to an edge of the base of an adjacent groove, wherein said edge of the base of the adjacent groove is the closest to the first groove, and (ii) a normal axis of the top surface of the column.

10. The display assembly of claim 1 , wherein the color filters are on top of the luminance enhancement structure.

11. The display assembly of claim 10 , wherein the ratio of the width of the top surface of each of the columns to the distance between the luminance enhancement structure and the top of a display fluid in the display cells is at least about 2.

12. The display assembly of claim 1 , wherein the color filters are placed between the luminance enhancement structure and the display device.

13. The display assembly of claim 12 , wherein there are dead spots between the color filters and the grooves of the luminance enhancement structures are aligned with the dead spots.

14. The display assembly of claim 1 , wherein the display cells are sandwiched between a common electrode layer and a backplane.

15. The display assembly of claim 1 , wherein the display device is in an X-Y plane, the columns and grooves are in the Y direction, and the light source is in a Y-Z plane.