Touch overlay for improved touch sensitivity

• US 5,386,219 A
• Filed: 07/28/1993
• Issued: 01/31/1995
• Est. Priority Date: 10/16/1991
• Status: Expired due to Term

• Current Assignee: AU Optronics Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Verrier, Guy F., Greanias, Evon C., Donaldson, Robert L.
• Primary Examiner(s): BRIER, JEFFERY A
• Application Number:
  US08/097,582
• Time in Patent Office: 552 Days
• Field of Search: 340/706, 340/709, 340/711, 340/712, 340/825.79, 340/825.81, 178/18, 178/19, 341/23, 341/26, 341/33, 345/179, 345/182, 345/183, 345/104, 345/173, 345/174, 345/175, 345/176
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer

Abstract

An improved touch overlay for the viewing surface of a display for detecting both finger touch and stylus location is disclosed. An upper and a lower set of transparent conductors are disposed on at least one transparent flexible insulating substrate and are oriented orthogonally with respect to each other. Depending on the orientation of the transparent conductors, top and bottom cover layers may be added to the overlay. The separation between the upper and lower conductors and a separation from the user'"'"'s finger on the top surface of the overlay from the upper conductors is optimized. To speed finger touch sensing, the ambient capacitance of the overlay is reduced by increasing the separation between the upper and lower conductors layers. For improved operation, the present invention features a separation of at least 3 mils between upper and lower conductors. The separation between the top surface and the upper conductors is held to a minimum consistent with the preservation of integrity of the upper conductors when stylus pressure is applied. Means are also included in the overlay to improve the durability of the overlay with respect to repeated stylus pressure on top surface.

Claims

1. A touch overlay for a viewing surface of a display for detecting both finger touch or stylus location comprising:

a set of transparent, lower conductors in a parallel arrangement on a surface of a lower flexible, transparent, insulating substrate;

a set of transparent, upper conductors in a parallel arrangement on a surface of an upper flexible, transparent, insulating substrate, the upper conductors oriented orthogonally from the lower conductors and spaced at a distance greater than 3 mils to reduce the ambient capacitance of the overlay and increase speed of operation in finger touch mode;

a protective top cover of a flexible, transparent, insulating material disposed over said upper substrate to protect the upper conductors during contact by a stylus, the top cover having a top surface for contact by a finger and a stylus; and

at least one adhesive layer to bond the lower substrate and upper substrate together;

wherein the separation between the top surface and the upper conductors is no more than 3 mils.

2. The touch overlay as recited in claim 1 which further comprises means to restrict elongation of the transparent upper and lower conductors when subjected to repeated pressure by a stylus.

3. The touch overlay as recited in claim 2, wherein the lower conductors are disposed on the lower substrate and the upper conductors are disposed on the upper substrate, and both conductors face up, away from the viewing surface of the display, being subjected to compression forces at the midpoint of a deflection caused by a stylus on the top surface.

4. The touch overlay as recited in claim 2, wherein the lower and upper substrates are a single substrate, the lower conductors face down, toward the display and the upper conductors face up, away from the display and both lower and upper conductors are disposed on the single substrate.

5. The touch overlay as recited in claim 4, which further comprises a bottom cover disposed under the lower conductors.

6. The touch overlay as recited in claim 4, which further comprises an adhesive layer to attach the overlay directly on the viewing surface of the display.

7. The touch overlay as recited in claim 1, wherein at least one adhesive layer is matched in hardness to the substrate and top cover layers to prevent elongation of the upper and lower conductors.

8. The touch overlay as recited in claim 1 which further comprises a split bus structure to which the lower and upper conductors are connected, a first fraction of the lower conductors connected to a bus located at a first edge of the overlay, a second fraction of the lower conductors which comprises the remainder of the lower conductors connected to a bus located at a second edge of the overlay opposite to the first side, a first fraction of the upper conductors connected to a bus located at a third edge of the overlay, a second fraction of the upper conductors which comprises the remainder of the upper conductors connected to a bus located at a fourth edge of the overlay opposite to the third side, the lower and upper conductors crossing only bus wires located in the bus to which they are connected, whereby the ambient capacitance of the overlay is reduced to speed operation in finger touch mode.

9. The touch overlay as recited in claim 8, wherein each of the upper and lower conductors extends only as far as necessary into the bus to which it is connected to connect to a bus wire in the bus, whereby the ambient capacitance of the overlay is reduced to speed operation in finger touch mode.

10. A touch overlay for a viewing surface of a display for detecting both finger touch or stylus location comprising:

a flexible, transparent, insulating substrate having a lower and upper surface;

a set of transparent, lower conductors in a parallel arrangement on the lower surface of the substrate;

a set of transparent, upper conductors in a parallel arrangement on the upper surface of the substrate, the upper conductors oriented orthogonally from the lower conductors;

a top cover of flexible, transparent, insulating material disposed over the upper conductors to protect the upper conductors during contact by a stylus, the top cover having a top surface for contact by a finger and a stylus; and

,

an adhesive layer to bond the substrate and top cover layers together;

wherein the substrate has a thickness greater than 3 mils to reduce the ambient capacitance of the overlay and increase speed of operation in finger touch mode, and the aggregate thickness of the top cover and adhesive layer are no more than 3 mils.

11. The touch overlay as recited in claim 10, which further comprises a bottom cover disposed under the lower conductors.

12. The touch overlay as recited in claim 10, which further comprises an adhesive layer to attach the overlay directly on the viewing surface of the display.

13. The touch overlay as recited in claim 10, which further comprises a split bus structure to which the lower and upper conductors are connected, a first fraction of the lower conductors connected to a bus located at a first edge of the overlay, a second fraction of the lower conductors which comprises the remainder of the lower conductors connected to a bus located at a second edge of the overlay opposite to the first side, a first fraction of the upper conductors connected to a bus located at a third edge of the overlay, a second fraction of the upper conductors which comprises the remainder of the upper conductors connected to a bus located at a fourth edge of the overlay opposite to the third side, the lower and upper conductors crossing only bus wires located in the bus to which they are connected, whereby the ambient capacitance of the overlay is reduced to speed operation in finger touch mode.

14. The touch overlay as recited in claim 13, wherein each of the upper and lower conductors extends only as far as necessary into the bus to which it is connected to connect to a bus wire in the bus, whereby the ambient capacitance of the overlay is reduced to speed operation in finger touch mode.

15. An improved finger touch and stylus detection system for use at a viewing surface of a display comprising:

a set of transparent, lower conductors in a parallel arrangement on a surface of a flexible, transparent, insulating lower substrate;

a set of transparent, upper conductors in a parallel arrangement on a surface of a flexible, transparent, insulating upper substrate, the upper conductors oriented orthogonally from the lower conductors and spaced at a distance greater than 3 mils to reduce the ambient capacitance of the overlay and increase speed of operation in finger touch mode;

a top cover of a flexible, transparent, insulating material disposed over the upper conductors to protect the upper conductors during contact by a stylus, the top cover having a top surface for contact by a finger or a stylus; and

, at least one adhesive layer to bond the substrate and top cover layers together;

wherein the separation between the top surface and the upper conductors is no more than 3 mils;

a capacitive measurement means to detect finger input which runs more quickly when the ambient capacitance of the touch overlay is reduced;

a radiative signal source for driving selected conductors of the touch overlay during stylus detection;

a stylus for receiving signals produced by the conductors when driven by the radiative signal source;

a radiative signal measurement means coupled to the stylus for measuring the received signals;

a switchable path coupled to the upper and lower conductors, the capacitive measurement means, and the radiative signal source having a control input, for connecting selected conductors to the capacitive measurement means or radiative signal source for finger touch or stylus detection, respectively, in response to appropriate control signals being applied to the control input; and

a control processor coupled to the capacitive measurement means, the radiative signal measurement means and the switchable path, for receiving measured capacitance values for finger touch detection, for receiving measured radiative signal values for stylus detection, and for producing the control signals to the control input of the switchable path.

16. The touch system as recited in claim 15, wherein the overlay further comprises means to restrict elongation of the transparent upper and lower conductors when subjected to repeated pressure by a stylus.

17. The touch system as recited in claim 15, wherein the capacitive measurement means comprises a variable frequency oscillator circuit.

18. The touch system as recited in claim 16, wherein the lower conductors are disposed on the lower substrate and the upper conductors are disposed on the upper substrate, and both conductors face up, away from the viewing surface of the display, being subjected to compression forces at the midpoint of a deflection caused by a stylus on the top surface.

19. The touch system as recited in claim 16, wherein the lower conductors face down, toward the display and the upper conductors face up, away from the display and both lower and upper conductors are disposed on the same substrate.

20. The touch system as recited in claim 19, wherein the overlay further comprises a bottom cover disposed under the lower conductors.

21. The touch system as recited in claim 19, wherein the overlay further comprises an adhesive layer to attach the overlay directly on the viewing surface of the display.

22. The touch system as recited in claim 15, wherein at least one adhesive layer is matched in hardness to the substrate and top cover layers to prevent elongation of the upper and lower conductors.

23. The touch system as recited in claim 15, wherein the overlay comprises a split bus structure to which the lower and upper conductors are connected, a first fraction of the lower conductors connected to a bus located at a first edge of the overlay, a second fraction of the lower conductors which comprises the remainder of the lower conductors connected to a bus located at a second edge of the overlay opposite to the first side, a first fraction of the upper conductors connected to a bus located at a third edge of the overlay, a second fraction of the upper conductors which comprises the remainder of the upper conductors connected to a bus located at a fourth edge of the overlay opposite to the third side, the lower and upper conductors crossing only bus wires located in the bus to which they are connected, whereby the ambient capacitance of the overlay is reduced to speed operation in finger touch mode.

24. The touch system as recited in claim 23, wherein each of the upper and lower conductors extends only as far as necessary into the bus to which it is connected to connect to a bus wire in the bus, whereby the ambient capacitance of the overlay is reduced to speed operation in finger touch mode.

25. The touch system recited in claim 15, wherein the capacitive measurement means includes a variable frequency oscillator and means for counting the pulses of the oscillator as a measurement of capacitance for the lower and upper conductors.

26. The touch system of claim 25 including means for increasing the number of pulses counted for the lower conductor when the the lower and upper conductors are at different distances from the top cover.

27. The touch system of claim 26 wherein the number of pulses counted for the lower conductor is given by the relationship N(2)=1.5N(1) where N(2) is the number of pulses counted for the lower conductor and N(1) is the number of pulses counted for the upper conductor by the capacitance measuring means.

28. A touch overlay for a viewing surface of a display for detecting both finger touch or stylus location comprising:

a set of transparent, lower conductors which face down in a parallel arrangement on a surface of a lower flexible, transparent, insulating substrate;

a set of transparent, upper conductors which face down in a parallel arrangement on a surface of an upper flexible, transparent, insulating substrate, the upper conductors oriented orthogonally from the lower conductors and spaced at a distance greater than 3 mils to reduce the ambient capacitance of the overlay and increase speed of operation in finger touch mode;

a top cover of a flexible, transparent, insulating material disposed over said upper substrate to protect the upper conductors during contact by a stylus, the top cover having a top surface for contact by a finger and a stylus; and

at least one adhesive layer to bond the lower substrate and upper substrate together.