CONTRAST ENHANCEMENT FOR AN ELECTRONIC DISPLAY DEVICE BY USING A BLACK MATRIX AND LENS ARRAY ON OUTER SURFACE OF DISPLAY

• US 20020050958A1
• Filed: 02/16/1999
• Published: 05/02/2002
• Est. Priority Date: 02/17/1998
• Status: Active Grant

• Current Assignee: MEC Management, LLC (Three Affiliated Tribes of the Fort Berthold Reservation, North Dakota)
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: STEWART, ROGER GREEN, MATTHIES, DENNIS LEE, ATHERTON, JAMES HAROLD, SHEN, ZILAN
• Granted Patent: US 6,476,783 B2
• Time in Patent Office: Days
• US Class Current: 345/55
• CPC Class Codes: G02F 1/13336 Combining plural substrates to produce large-area displays, e.g. tiled displays
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• CPC Class Codes: G09G 2300/026 Video wall, i.e. juxtaposition of a plurality of screens to create a display screen of bigger dimensions
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2320/048 using evaluation of the usage time
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H10K 50/85 Arrangements for extracting light from the devices
• CPC Class Codes: H10K 50/858 comprising refractive means, e.g. lenses
• CPC Class Codes: H10K 50/86 Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 50/865 comprising light absorbing layers, e.g. light-blocking layers
• CPC Class Codes: H10K 59/17 Passive-matrix OLED displays
• CPC Class Codes: H10K 59/18 Tiled displays

Abstract

A display device having features which enhance the contrast of displayed images includes a pixel structure that defines an active pixel area and an inactive pixel area. The display device may be an emissive device such as an OLED or electroluminescent device, a transmissive device such as a liquid crystal light-valve device or a reflective device, such as a Bistable, Reflective Cholesteric (BRC) liquid crystal device. The ratio of the active pixel area to the total pixel area is less than 50 percent. The display device includes a transparent cover plate having a black matrix formed on the viewer side of the cover plate. The display device may be a tiled display in which case the black matrix is formed on an integrator plate to which the individual tiles are bound to form the complete display device. For reflective or emissive display materials, the display device includes an electronics section including a circuit board which provides driving signals for the pixels of the display device. The electronics section is bound to the display section by an adhesive. To provide a light-absorptive background for the active pixel elements, the circuit board or the adhesive are colored black. The individual pixel elements of the display device include four sub-pixel components separated by portions of the inactive pixel area, which four sub-pixel components together define the active area of the pixel. A lens system is provided on the viewer surface of the display to concentrate light emitted by the active area of the pixel elements into a smaller area, thus decreasing the aperture of the display. Areas between the lenses on the viewer surface of the display are coated with a black material to form a black matrix. A black material is selectively deposited on the front cover plate before applying the metal row electrodes to prevent the row electrodes from providing a reflective surface to the viewer.

Claims

1. A display device having a plurality of picture element (pixels), comprising:

a pixel structure for the plurality of pixels which pixel structure defines a pixel area including an active pixel area and an inactive pixel area in which only the active pixel area provides light and in which the ratio of the active pixel area to the pixel area is less than 50 percent;

a transparent cover plate having a outer surface and an inner surface wherein the inner surface is in close proximity to the pixel area;

a black matrix formed on the outer surface of the transparent cover plate, the black matrix defining openings surrounded by a dark colored material, the openings being aligned with the active pixel areas of the display device.

2. A display device according to claim 1, wherein the pixel area has width P including an active pixel area which has a width d_p and the transparent cover plate has an index of refraction n_glass, which defines a critical angle of Θ

c, and a thickness t_glass and the black matrix is formed from dark-colored stripes having a width W_m defined by the inequality W_m≦

P−

2 (t_glass tan (Θ

c))−

d_p.

3. A display device according to claim 2, wherein the width, W_m, of the black matrix stripes is further defined by the inequality W_m≧

2 d_c.

4. A display device according to claim 1, wherein transparent cover plate has an index of refraction n_glass, which defines a critical angle of Θ

c, and a thickness t_glass and the black matrix is formed from dark-colored stripes having a width W_m defined by the inequality W_m≧

2 d_c.

5. A display device according to claim 1, further comprising a filter positioned over the plurality of pixels to pass light provided by the active pixel areas and to attenuate ambient reflected light which passes through the transparent cover plate, the patterned color filter and is reflected by the pixel areas of the display device.

6. A display device according to claim 5, wherein the filter is a neutral gray filter.

7. A display device according to claim 5, wherein the filter is a patterned color filter.

8. A display device according to claim 5, wherein the filter is a polarizing filter.

9. A display device according to claim 1, wherein the outer surface of the transparent cover plate includes an anti-reflective coating.

10. A display device according to claim 1 wherein the pixel structure includes a row electrode and a column electrode for driving the pixel structure, wherein the active pixel area includes a display material selected from a group consisting of an emissive display material a reflective display material and the display device includes an electronics section, coupled to the inner surface of the transparent cover plate, the electronics section including a circuit board which provides electrical signals to the row electrodes and the column electrodes of the pixel structure.

11. A display device according to claim 10, wherein the circuit board is made from a dark-colored material to provide a light-absorptive background for the active pixel area.

12. A display device according to claim 10, wherein the circuit board is joined to the inner surface of the transparent cover plate by an adhesive and the adhesive includes dark-colored material whereby the assembled display device provides a light-absorptive background for the active pixel area.

13. A display device according to claim 10, wherein the column electrodes are transparent and are formed directly on the transparent cover plate, the display material is deposited on the column electrodes and row electrodes are deposited on the display material and on portions of the transparent cover plate, wherein, before depositing the row electrodes, the portions of the transparent cover plate on to which the row electrodes are to be deposited are coated with a dark-colored material.

14. A display device according to claim 1, wherein the display device is a tiled display device including an optical integrator plate and the black matrix is formed on the surface of the optical integrator plate on to which the individual tiles are mounted.

15. A display device according to claim 1, wherein the active area of the pixel structure defines a plurality of spaced sub-pixel elements separated by portions of the inactive pixel area, wherein the sub-pixel elements together define an aperture of less than 50 percent.

16. A display device according to claim 15, wherein the active area of the pixel structure defines a plurality of spaced sub-pixel elements separated by portions of the inactive pixel area, wherein the sub-pixel elements together define an aperture of approximately 25 percent.

18. A display device according to claim 17, further including a black matrix structure coupled to the outer surface of the lens structure, the black matrix structure covering areas of the lens structure which do not transmit light to a viewer.

19. A display device according to claim 17, wherein the individual lenses protrude from the transparent cover plate and have relatively steeply angled sides, the angles of the sides of the lenses being sufficient to form a light trap such that ambient light which enters the lens structure tends to be reflected internally in the lens structure and not to a viewer.

20. A display device according to claim 19, further including a black matrix structure coupled to the outer surface of the lens structure, the black matrix structure covering the sides of the lens structure.

21. A display device according to claim 20, wherein the black matrix structure has a index of refraction and the display device further includes a coating of a material having a lower index of refraction than the black matrix structure which is positioned between the sides of the lens structure and the black matrix structure.

22. A display device according to claim 19, further including a reflective material covering the sides of the lens structure.

23. A display device according to claim 17, further comprising a filter positioned over the plurality of pixels to pass light provided by the active pixel areas and to attenuate ambient reflected light which passes through the transparent cover plate and the apertures of the lens structure, the patterned color filter and is reflected by the pixel areas of the display device.

24. A display device according to claim 23, wherein the filter is a neutral gray filter.

25. A display device according to claim 23, wherein the filter is a patterned color filter.

26. A display device according to claim 23, wherein the filter is a polarizing filter.

27. A display device according to claim 17 wherein the pixel structure includes a row electrode and a column electrode for driving the pixel structure, wherein the active pixel area includes a display material selected from a group consisting of an emissive display material a reflective display material and the display device includes an electronics section, coupled to the inner surface of the transparent cover plate, the electronics section including a circuit board which provides electrical signals to the row electrodes and the column electrodes of the pixel structure.

28. A display device according to claim 27, wherein the circuit board is made from a dark-colored material to provide a light-absorptive background for the active pixel area.

29. A display device according to claim 27, wherein the circuit board is joined to the inner surface of the transparent cover plate by an adhesive and the adhesive includes dark-colored material whereby the assembled display device provides a light-absorptive background for the active pixel area.

17. A display device having a plurality of picture element (pixels), comprising:

a pixel structure for the plurality of pixels which pixel structure defines a pixel area including an active pixel area and an inactive pixel area in which only the active pixel area provides light and in which the ratio of the active pixel area to the pixel area is less than 50 percent;

a transparent cover plate having a outer surface and an inner surface wherein the inner surface is in close proximity to the pixel area; and

a lens structure having an inner surface and an outer surface, the inner surface of the lens structure being coupled to the outer surface of the transparent cover plate, the lens structure defining a plurality of lenses, each lens being positioned with respect to an active pixel area to condense light provided by a first area of the active pixel element into an aperture of the lens, wherein the aperture has an area smaller than the first area of the active pixel element.

30. A display device having a plurality of picture element (pixels), comprising:

a display section including the plurality of pixels, each pixel having a pixel structure which defines a pixel area including an active pixel area and an inactive pixel area in which only the active pixel area provides light, wherein the pixel structure includes a row electrode and a column electrode for driving the pixel structure and the active pixel area includes a display material selected from a group consisting of an emissive display material a reflective display material;

an electronics section, coupled to the display section, the electronics section including a circuit board which provides electrical signals to the row electrodes and the column electrodes of the pixel structure; and

an adhesive which binds the electronics section to the display section.

31. A display device according to claim 30, wherein the circuit board is made from a dark-colored material to provide a light-absorptive background for the active pixel area.

32. A display device according to claim 30, wherein the adhesive includes dark-colored material whereby the assembled display device provides a light-absorptive background for the active pixel area.

33. A display device according to claim 30, wherein the column electrodes are transparent and are formed directly on the transparent cover plate, the display material is deposited on the column electrodes and row electrodes are deposited on the display material and on portions of the transparent cover plate, wherein, before depositing the row electrodes, the portions of the transparent cover plate on to which the row electrodes are to be deposited are coated with a dark-colored material.

34. A display device according to claim 30, wherein the display material is an emissive display material and the display device further comprises a filter positioned over the plurality of pixels to pass light provided by the active pixel areas and to attenuate ambient reflected light which passes through the transparent cover plate, the patterned color filter and is reflected by the pixel areas of the display device.

35. A display device according to claim 34, wherein the filter is a neutral gray filter.

36. A display device according to claim 34, wherein the filter is a patterned color filter.

37. A display device according to claim 34, wherein the filter is a polarizing filter.

38. A display device according to claim 30, further including a transparent cover plate having an inner surface and an outer surface, the inner surface being in close proximity to the plurality of pixels and the outer surface including an anti-reflective coating.