LUMINANCE ENHANCEMENT STRUCTURE FOR REFLECTIVE DISPLAY DEVICES

• US 20090231245A1
• Filed: 03/04/2009
• Published: 09/17/2009
• Est. Priority Date: 03/11/2008
• Status: Active Grant

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: SiPix Imaging, Inc. (E Ink Holdings Incorporated)
• Inventors: Lin, Craig
• Granted Patent: US 8,395,836 B2
• Time in Patent Office: Days
• US Class Current: 345/77
• CPC Class Codes: G02F 1/133507 Films for enhancing the luminance
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 3/344 based on particles moving in a fluid or in a gas, e.g. electrophoretic devices electrophoretic devices per se G02F1/167

Abstract

The present invention is directed to luminance enhancement structure for reflective display devices. The luminance enhancement structure comprises grooves and columns, wherein said grooves have a triangular cross-section and a top angle, and said grooves and columns are in alternating order and in a continuous form in one direction. The luminance enhancement structure not only can reduce the total internal reflection, but also especially can enhance the on-axis brightness of a display device.

Claims

1. A luminance enhancement structure, comprising grooves and columns, wherein said grooves have a triangular cross-section and a top angle, said grooves and columns are in alternating order and in a continuous form in one direction.

2. The structure of claim 1, wherein the surface of the grooves is uncoated.

3. The structure of claim 1, wherein the top angles of the grooves are substantially equal.

4. The structure of claim 3, wherein the top angle is in the range of about 5°

to about 50°

.

5. The structure of claim 4, wherein the top angle is in the range of about 20°

to about 40°

.

6. The structure of claim 1, wherein the space within the grooves is filled with air or a low refractive index material.

7. The structure of claim 1, which is formed from a material having a refractive index of about 1.4 to about 1.7.

8. The structure of claim 1, comprising an angle β

which is smaller than the critical angle at the boundary between the top surface of the luminance enhancement structure and air, which angle β

is the angle formed at the intersection of (i) the line connecting the top point of a first groove to the 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) the normal axis of the top surface of the column.

9. A reflective display assembly comprising:

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

(b) a luminance enhancement structure on top of the display panel on the viewing side of the display device, said luminance enhancement structure comprises grooves and columns, wherein said grooves have a triangular cross-section and a top angle, and said grooves and columns are in alternating order and in continuous form in one direction.

10. The display assembly of claim 9, wherein the top angles of the grooves are substantially equal.

11. The display assembly of claim 9, wherein said columns have a top surface which is in optical contact with said top substrate layer.

12. The display assembly of claim 11, wherein said top substrate layer has a thickness in the range of about 1 μ

m to about 175 μ

m.

13. The display assembly of claim 12, wherein said top substrate layer has a thickness in the range of about 1 μ

m to about 25 μ

m.

14. The display assembly of claim 10, wherein said top angle is in the range of about 5°

to about 50°

.

15. The display assembly of claim 14, wherein said top angle is in the range of about 20°

to about 40°

.

16. The display assembly of claim 9, wherein the surface of the grooves is uncoated.

17. The display assembly of claim 9, wherein the space within the grooves is filled with air or a low refractive index material.

18. The display assembly of claim 9, wherein said luminance enhancement structure comprises an angle β

which is smaller than the critical angle at the boundary between the top surface of the luminance enhancement structure and air, which angle β

is the angle formed at the intersection of (i) the line connecting the top point of a first groove to the 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) the normal axis of the top surface of the column.

19. The display assembly of claim 9, wherein the ratio of the width of the top surface of the columns to the distance between the luminance enhancement structure and the top of the display fluid is at least about 2.

20. The display assembly of claim 9, further comprising a common electrode layer and a backplane.