Low reflectivity flat panel display

• US 20030160740A1
• Filed: 02/27/2003
• Published: 08/28/2003
• Est. Priority Date: 02/27/2002
• Status: Active Grant

• Current Assignee: Innovative Solutions and Support Incorporated
• Original Assignee: Innovative Solutions and Support Incorporated
• Inventors: Hedrick, Geoffrey S.M.
• Granted Patent: US 6,879,365 B2
• Time in Patent Office: Days
• US Class Current: 345/32
• CPC Class Codes: G02F 1/133502 Antiglare, refractive index matching layers
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 2201/38 Anti-reflection arrangements
• CPC Class Codes: G02F 2202/28 Adhesive materials or arrangements

Abstract

An improved flat panel display provides reduced reflection of incident light on the display to improve display visibility. The display includes a transparent top cover panel such as glass which is bonded or laminated to the display polarizer. The outer viewing surface of the top cover panel carries a plurality of integral surface features defined in the surface, which may comprise etched bumps or micro-machined tetrahedron-shaped protuberances that may be truncated, smoothed, and/or variously oriented and sized to further reduce incident light reflectivity. A multi-layer HEA coating on the featured surface defines a graduated transition layer with an index of refraction that gradually, and preferably smoothly, varies from layer to layer of the HEA coating from the index of refraction of the top cover panel to the index of refraction of the ambient air or other material which the outermost viewable surface of the display presents an image to an observer or viewer.

Claims

1. A flat panel display for providing improved resolution through decreased reflection of incident light, comprising:

a substrate;

an array of electrodes disposed on said substrate for activating selected pixels of an array of pixels;

a polarizer disposed on said electrode array for polarizing light received by said electrode array;

a layer of anti-reflective transparent material disposed on said polarizer, said transparent material having an index of refraction and a viewing surface containing a plurality of surface details distributed about the viewing surface; and

a layer of anti-reflective coating disposed on said viewing surface and having an index of refraction no greater than the index of refraction of said transparent material, said transparent material and said anti-reflective coating producing very low actual and viewer-perceived reflectance while providing a clear and high contrast display of display-generated images to a viewer of said display.

2. The display of claim 1, wherein said surface details comprise bumps arranged in a matrix on said viewing surface.

3. The display of claim 1, wherein said surface details comprise bumps arranged in a random pattern on said viewing surface.

4. The display of claim 1, wherein said surface details comprise bumps having substantially equal heights relative to said viewing surface.

5. The display of claim 1, wherein said surface details comprise bumps having a range of different heights relative to said viewing surface.

6. The display of claim 1, wherein said layer of transparent material is laminated to said polarizer.

7. The display of claim 1, wherein said layer of transparent material is bonded to said polarizer by a bonding agent comprising one of silicon adhesive and a transparent liquid epoxy, said bonding agent having an index of refraction substantially equal to the index of refraction of said transparent material layer.

8. The display of claim 1, wherein said layer of anti-reflective coating comprises (n) layers of an HEA anti-reflective coating each having an associated index of refraction and disposed one atop another from a first layer on said viewing surface to an outermost layer most remote from the viewing surface for interfacing an environment in which said display is used, said first layer having an index of refraction substantially equal to the index of refraction of the transparent material and said outermost layer having an index of refraction substantially equal to an index of refraction of the environment, and the n−

2 layers between said first and outer layers having indices of refraction that gradually vary from and between the indices of refraction of the first and outer layers.

9. The display of claim 1, wherein said surface details comprise angular tetrahedrons.

10. The display of claim 9, wherein said tetrahedrons are arranged on said viewing surface in a matrix.

11. The display of claim 9, wherein said tetrahedrons are arranged on said viewing surface in a random pattern.

12. The display of claim 9, wherein each said tetrahedron has a longitudinal axis and a height relative to said viewing surface.

13. The display of claim 12, wherein said tetrahedrons have substantially equal heights relative to the viewing surface.

14. The display of claim 9, wherein each said tetrahedron has a truncated apex.

15. The display of claim 12, wherein each said tetrahedron has a common axial alignment.

16. The display of claim 12, wherein each said tetrahedron has a random axial alignment.

17. In a flat panel display operative for generating an image viewable by an observer of the display situated before a front of the display and through an ambient medium that is disposed between the observer and the display and which has an associated index of refraction,

a transparent material sheet located at the front of the display and through which an image operatively generated by the display is viewable by an observer situated before a viewing surface of the transparent material sheet, said material sheet having an associated index of refraction,

a plurality of outwardly projecting surface features defined unitarily on and distributed about the viewing surface of the transparent material sheet so that the surface features project outwardly toward the observer, and

a multi-layer HEA coating applied over said viewing surface of the transparent material sheet so as to cover said plural surface features and thereby provide an anti-reflective coating over said material sheet viewing surface, each layer of the multi-layer coating having a respective index of refraction, the index of refraction of a first layer of the multiple coating layers which is disposed against said viewing surface being substantially equal to the index of refraction of the material sheet, the index of refraction of an outermost layer of the multiple coating layers which is most remote from said first layer being substantially equal to the index of refraction of the ambient medium, and the index of refraction of each other layer of the multiple coating layers between the first and outermost layers being between the indices of refraction of said first and outermost layers so that the multi-layer HEA coating has an effective index of refraction that gradually varies from the substantially the index of refraction of the material sheet to substantially the index of retraction of the ambient medium to thereby define a graduated transition layer for minimized reflectance between the display and the observer of light incident on the display.

18. In a flat panel display in accordance with claim 17, said surface features comprising a plurality of mounds distributed about the viewing surface of the material sheet and defined by etching of the viewing surface to form an irregular viewing surface.

19. In a flat panel display in accordance with claim 17, said surface features comprising a plurality of irregular mounds distributed about the viewing surface of the material sheet and defined by etching of the viewing surface to form a predeterminately frosted viewing surface.

20. In a flat panel display in accordance with claim 17, said surface features comprising a plurality of tetrahedron-shaped projections distributed about the viewing surface of the material sheet and each having a base and a top portion.

21. In a flat panel display in accordance with claim 20, wherein each said tetrahedron-shaped projection is truncated at its top portion.

22. In a flat panel display in accordance with claim 21, wherein said truncated top portions are rounded.

23. In a flat panel display in accordance with claim 20, wherein the bases of said plural tetrahedron-shaped projections defined on said viewing surface are variously oriented about the viewing surface.

24. In a flat panel display in accordance with claim 20, wherein said plural tetrahedron-shaped projections defined on said viewing surface project outwardly toward the observer by various different amounts.

25. In a flat panel display in accordance with claim 20, wherein said plural tetrahedron-shaped projections defined on said viewing surface have bases of variously different aspect ratios.

26. In a flat panel display in accordance with claim 20, said plural tetrahedron-shaped projections being defined at non-regular locations on and about said viewing surface.

27. In a flat panel display in accordance with claim 20, said plural tetrahedron-shaped projections being defined at locations along a predefined grid on and about said viewing surface.

28. A method for improving observer visibility of images generated by a flat panel display as viewed by an observer situated before a transparent material sheet through which the display-generated images are viewable and which is located at the front of the flat panel display, wherein the observer views the display-generated images through an ambient environment disposed between the observer and the display and which has an associated environment index of refraction, comprising the steps of:

processing a front viewing surface of a transparent material sheet of the display through which an image operatively generated by the display is viewable by the observer situated before the viewing surface to define unitarily on the viewing surface a plurality of outwardly projecting surface features distributed about the viewing surface of the transparent material sheet so that the surface features project outwardly toward the observer, the material sheet having an associated material index of refraction, and said surface features being configured for reducing direct reflection from the viewing surface toward the observer of light incident on the display; and

applying a multi-layer HEA coating to the viewing surface on which the plural surface features are defined so as to cover the plural surface features and thereby provide an anti-reflective coating over the material sheet viewing surface, each layer of the multi-layer HEA coating having a respective layer index of refraction, the layer index of refraction of a first layer of the multiple coating layers which is disposed against said viewing surface being substantially equal to the material index of refraction of the material sheet, the layer index of refraction of an outermost layer of the multiple coating layers which is most remote from said first layer being substantially equal to the medium index of refraction of the ambient medium, and the index of refraction of each other layer of the multiple coating layers being between the layer indices of refraction of said first and outermost layers so that the multi-layer HEA coating has an effective index of refraction that gradually varies from the material index of refraction of the material sheet to the medium index of retraction of the ambient medium to thereby define a graduated transition layer for minimized reflectance between the display and the observer of light incident on the display.

29. A method in accordance with claim 28, where said processing step comprises etching the viewing surface of the material sheet so that the surface features comprise a plurality of mounds distributed about the viewing surface of the material to form an irregular viewing surface through which display-generated images are viewable by the observer.

30. A method in accordance with claim 28, wherein said processing step comprises machining the viewing surface of the material sheet to unitarily form on the viewing surface a plurality of tetrahedron-shaped surface features distributed about the viewing surface and each having a base and a top portion that projects outwardly toward the observer.

31. A method in accordance with claim 30, wherein said processing step further comprises machining the tetrahedron-shaped surface features to yield truncated apexes.

32. A method in accordance with claim 30, wherein said processing step further comprises forming said plurality of tetrahedron-shaped surface features in substantial axial alignment with respect to each other.

33. A method in accordance with claim 30, wherein said processing step further comprises forming said plurality of tetrahedron-shaped surface features in random axial alignment with respect to each other.