Integrated liquid crystal display and digitizer having a black matrix layer adapted for sensing screen touch location

• US 5,847,690 A
• Filed: 10/24/1995
• Issued: 12/08/1998
• Est. Priority Date: 10/24/1995
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Krukar, Richard H., Kmetz, Allan Robert, Lu, Po-Yen, Boie, Robert Albert, Gottscho, Richard Alan, Morris, John Robert Jr.
• Primary Examiner(s): Brier, Jeffery
• Assistant Examiner(s): Bell, Paul A.
• Application Number:
  US08/547,636
• Time in Patent Office: 1,141 Days
• Field of Search: 345/104, 345/173, 345/174, 345/179, 359/54, 359/68, 349/110
• US Class Current: 345/104
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

A unitary display and sensing device integrates liquid crystal display module elements of a liquid crystal display module for detecting input on a flat panel display screen with the capability for digitizing the detected inputs. In accordance with an illustrative embodiment of the present invention, display elements of a liquid crystal display module are modified to sense input on the display screen. An electrical signal is applied to modified display elements of the liquid crystal display module so that contact with a surface portion of the display screen produces an output signal indicative of its location. The integrated display and sensing device is active matrix addressed for finger input, but may also incorporate display systems for active pen input.

Claims

1. A liquid crystal display comprising:

a display screen;

an active matrix plate spaced apart from the display screen wherein the active matrix plate has a plurality of switching elements connected to an array of thin film transistors formed thereon;

a color filter plate positioned between the display screen and the active matrix plate wherein the color filter plate has a layer of black matrix material formed on a surface thereof; and

a transparent conductive layer positioned between the active matrix plate and the color filter plate wherein the layer of black matrix material and the transparent conductive layer are adapted to sense the location of an object touching the display screen based upon the relative size of the displacement current generated at the point of contact between the object and the display screen.

2. The liquid crystal display of claim 1 wherein the object is a finger.

3. The liquid crystal display of claim 1 wherein the object is a stylus.

4. The liquid crystal display of claim 1 wherein the layer of black matrix material is patterned into a plurality of strips of conducting material which are separated from each other by a plurality of isolation areas.

5. The liquid crystal display of claim 1 wherein the plurality of switching elements are adapted to have a plurality of gate lines and a plurality of row lines and wherein at least one of the plurality of isolation areas are aligned to one of the plurality of gate lines and the plurality of row lines of the plurality of switching elements on the active matrix plate.

6. The liquid crystal display of claim 4 wherein the layer of black matrix material is further patterned to have a plurality of resistive strings and a plurality of contact pads.

7. The liquid crystal display of claim 4 wherein at least one of the isolation areas is non-continuous.

8. The liquid crystal display of claim 7 further comprising a color filter array having a red filter, a blue filter and a green filter, wherein the at least one isolation area that is non-continuous is aligned to the blue filter of the color filter array.

9. A method of sensing the location of an object touching a surface portion of a display screen of a liquid crystal display comprising the steps of:

applying a signal to a black matrix layer of a liquid crystal display wherein the black matrix layer is patterned into a plurality of stripes of conducting material which are separated from each other by a plurality of isolation areas, and wherein the signal generates a current in the black matrix layer; and

generating a displacement current in response to an object touching a portion of a display screen of the liquid crystal display wherein the black matrix layer and a transparent conductive layer of the liquid crystal display sense the location of the object touching the display screen based upon the relative size of the displacement current generated at the point of contact between the object and the display screen.

10. The method of claim 9 wherein the object is a stylus.

11. The method of claim 9 wherein the object is a finger.

12. The method of claim 9 further comprising applying the signal to a transparent conductor of the liquid crystal display.

13. A method of sensing the location of an object touching a surface portion of a display screen of a liquid crystal display comprising the steps of:

applying a signal to a black matrix layer and a transparent conductor of a liquid crystal display wherein the black matrix layer is patterned into a plurality of strips of conducting material which are separated from each other by a plurality of isolation areas, and wherein the signal generates a current in the black matrix layer; and

generating a displacement current in response to an object touching a portion of a display screen of the liquid crystal display wherein the black matrix layer and the transparent conductive layer of the liquid crystal display sense the location of the object touching the display screen based upon the relative size of the displacement current generated at the point of contact between the object and the display screen.