Contrast enhancement for an electronic display device by using a black matrix and lens array on outer surface of display

• US 6,476,783 B2
• Filed: 02/16/1999
• Issued: 11/05/2002
• Est. Priority Date: 02/17/1998
• Status: Expired due to Term

• Current Assignee: MEC Management, LLC (Three Affiliated Tribes of the Fort Berthold Reservation, North Dakota)
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: Shen, Zilan, Atherton, James Harold, Matthies, Dennis Lee, Stewart, Roger Green
• Primary Examiner(s): Saras, Steven
• Assistant Examiner(s): Bell, Paul A.
• Application Number:
  US09/250,347
• Publication Number:
  US 20020050958A1
• Time in Patent Office: 1,358 Days
• Field of Search: 349/44, 349/57, 349/73, 349/95, 349/110, 349/111, 349/122, 349/112, 349/137, 349/138, 349/56, 257/59, 257/91, 257/98, 257/435, 257/436, 257/437, 438/29, 438/30, 345/32, 345/55, 345/60, 345/76, 345/82, 345/84, 345/85, 345/80
• US Class Current: 345/82
• 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, which includes an emissive display material and an inactive pixel area in which only the active pixel area emits 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 where part of the emitted light from the active pixel area passes through the transparent cover plate and another part is reflected internally by the outer surface of the transparent cover plate;

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 and being in contact with the display and through which the emitted light from the active pixel area passes.

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≧

2d_c is the lateral distance traveled by the active pixel light emitted from a point within the transparent cover plate.

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≧

2d_cwherein d_c is the lateral distance traveled by the active pixel light emitted from a point within the transparent cover plate.

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 and the 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 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.

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, which includes an emissive display material and an inactive pixel area in which only the active pixel area emits 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 where part of the emitted light from the active pixel area passes through the transparent cover plate and another part is reflected interally by the outer surface of the transparent cover plate;

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 and being in contact with the display and through which the emitted light from the active pixel area passes and the black matrix being operable to block light emanating from the inactive pixel areas.