Touch sensor

• US 20030234769A1
• Filed: 06/25/2002
• Published: 12/25/2003
• Est. Priority Date: 06/25/2002
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Schulz, Stephen C., Cordeiro, Craig A., Bottari, Frank J., Cross, Elisa M., Chernefsky, Anthony F., Moshrefzadeh, Robert S., Kardauskas, Michael J.
• Granted Patent: US 7,154,481 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• 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
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells
• CPC Class Codes: G06F 3/0488 using a touch-screen or digitiser, e.g. input of commands through traced gestures

Abstract

A touch sensing method and a touch sensing device are described for sensing a location of a touch. When the touch sensing device is touched, a first conductive layer disposed on a supporting layer is deflected toward a second conductive layer. The touch location is determined by sensing the change in capacitance at the location of the touch. A change in capacitance at the touch location is sensed by driving one of the conductive layers with an electrical signal referenced to the other conductive layer and measuring the current flow between the conductive layers. The sensed change in capacitance is greater than a change in the external capacitance of the touch sensor.

Claims

1. A method for sensing a two-dimensional location of a touch on a touch sensor, comprising:

sensing a change in capacitance between a first transparent, conductive sheet and a second transparent, conductive sheet when at least a portion of the first transparent, conductive sheet is moved towards the second transparent, conductive sheet; and

determining the two-dimensional location of the touch from signals derived from the change in capacitance between the two transparent conductive sheets.

2. The method of claim 1, wherein the first transparent, conductive sheet is flexible, and moving the first transparent, conductive sheet towards the second transparent, conductive sheet at the location of the touch includes flexibly deflecting the first transparent, conductive sheet towards the second transparent, conductive sheet.

3. The method of claim 1, wherein sensing the change in capacitance further includes:

driving one of the transparent, conductive sheets with an electrical signal referenced to the other transparent, conductive sheet; and

measuring capacitive current flow between the first and second transparent, conductive sheets.

4. The method of claim 3, wherein measuring current flow includes measuring capacitive current flow at two or more peripheral locations on at least one of the first and second transparent, conductive sheets.

5. The method of claim 4, further comprising taking a ratio of the capacitive currents measured at two of the two or more peripheral locations and determining the two-dimensional location includes assigning a touch location to a position between the two peripheral locations based on the ratio of the capacitive currents

6. The method of claim 1, further comprising shielding the touch sensor from electromagnetic interference caused by a display device disposed on a display side of the touch sensor using the second transparent, conductive sheet.

7. The method of claim 1, further comprising detecting a touch force at the location of the touch.

8. The method of claim 1, wherein moving the first transparent, conductive sheet toward the second transparent, conductive sheet layer includes touching an outer surface of the touch sensor.

9. A method as recited in claim 1, further comprising touching the touch sensor with a touching object to deflect the first transparent, conductive sheet of the touch sensor towards the second transparent, conductive sheet.

10. The method of claim 9, wherein the touching object is substantially electrically insulating.

11. A touch sensor, comprising:

a first transparent, conductive sheet supported on a flexible, transparent supporting layer;

a second transparent, conductive sheet disposed to define a gap between the first and second transparent, conductive sheets, the first transparent, conductive sheet being flexible to allow local deformation towards the second transparent, conductive sheet due to a touch force without contacting the second transparent, conductive sheet so as to produce a change in capacitance between the first and second transparent, conductive sheets.

12. The touch sensor of claim 11, wherein the thickness of the supporting layer is greater than the thickness of the gap between the first and second conductive sheets.

13. The touch sensor of claim 11, wherein the supporting layer is comprised of PET.

14. The touch sensor of claim 11, further comprising at least one protective coating provided on at least one of the first and second conductive sheets, within the gap between the first and second conductive sheets.

15. The touch sensor of claim 14, wherein the thickness of the at least one protective coating is in the range of approximately 1 μ

m to 4 μ

m.

16. The touch sensor of claim 14 wherein the at least one protective coating has a refractive index less than the refractive index of its associated conductive sheet.

17. The touch sensor of claim 14, wherein at least one element is disposed within the gap to prevent the first and second conductive sheet from touching when the first conductive sheet is moved towards the second conductive sheet.

18. The touch sensor of claim 17, wherein the at least one element includes a plurality of spacers disposed in the gap between the first and second conductive sheets.

19. The touch sensor of claim 17, wherein the at least one element includes a layer of material disposed in the gap between the first and second conductive sheets.

20. The touch sensor of claim 14, wherein a dielectric material is disposed in the gap between the first and second conductive sheet.

21. The touch sensor of claim 20, wherein the dielectric material is a fluid.

22. The touch sensor of claim 20, wherein the fluid is a deformable, elastic material.

23. The touch sensor of claim 22, wherein the electrical properties of the dielectric material change when the dielectric material is compressed.

24. The touch sensor of claim 23, wherein the dielectric material is loaded with conductive particles.

25. The touch sensor of claim 24, wherein the conductive particles include at least one of metal particles, metal oxide particles, metal coated particles and metal oxide coated particles.

26. The touch sensor of claim 20, wherein the dielectric material is a piezoelectric material.

27. The touch sensor of claim 20, wherein the refractive index of the dielectric material is less than the refractive index of at least one of the first and second conductive sheets.

28. The touch sensor of claim 11, further comprising:

a controller coupled to the first and the second conductive sheets through a plurality of contacts to determine a two-dimensional position of the portion of the first conductive sheet moving towards the second conductive sheet.

29. The touch sensor of claim 28, wherein the controller drives one of the first and second conductive sheets with an electrical signal referenced to the other of the first and second conductive sheets, and measures capacitive current flow between the first and the second conductive sheets.

30. The touch sensor of claim 29, wherein capacitive current flow is measured at two or more peripheral locations on at least one of conductive sheets.

31. The touch sensor of claim 11, wherein the second conductive sheet shields the touch sensor from electromagnetic interference caused by a display device disposed below the touch sensor.

32. The touch sensor of claim 11, wherein at least one of the first and second conductive layers has a resistivity of no more than 2,000 ohms/square.

33. A touch sensor, comprising:

a first conductive layer, the first conductive layer being transparent and flexible;

a second conductive layer, the second conductive layer being transparent and disposed relative to the first conductive layer to define a gap between the first and second conductive layers, the first transparent, conductive layer being flexible to allow local deformation towards the second transparent, conductive layer due to a touch force without contacting the second transparent, conductive layer so as to produce a change in capacitance between the first and second transparent, conductive layers; and

a plurality of spacers located within the gap, the plurality of spacers being transparent and permitting movement of the first conductive layer towards the second conductive layer under a touch while maintaining a predetermined minimum distance between the first and second conductive layers.

34. The touch sensor of claim 33, wherein the predetermined distance is in a range of 5 to 500 μ

m.

35. The touch sensor of claim 33, wherein a separation distance between adjacent spacers is in a range of 20 to 5000 μ

m.

36. The touch sensor of claim 33, wherein the plurality of spacers is formed on a layer of the touch sensor.

37. The touch sensor of claim 36, wherein the spacers are formed of a UV curable material.

39. The touch sensor of claim 33, wherein at least one of the first and second conductive layers includes a protective coating.

40. The touch sensor of claim 39, wherein the plurality of spacers is formed integrally with the protective coating.

41. The touch sensor of claim 40, wherein a surface of the protective coating with integrated spacers is roughened so as to reduce glare and occurrence of Newton'"'"'s rings.

42. The touch sensor of claim 33, wherein the spacers are formed of a particle loaded material.

43. The touch sensor of claim 42, wherein the spacers are formed of a material loaded with silica particles.

44. A touch screen display system, comprising:

a touch screen for sensing a touch, including

a first transparent, conductive sheet supported on a flexible, transparent supporting layer;

a second transparent, conductive sheet disposed relative to the first transparent, conductive layer and defines a gap therebetween, the first transparent, conductive sheet being flexible to allow local deformation towards the second transparent, conductive sheet due to a touch force without contacting the second transparent, conductive sheet so as to produce a change in capacitance between the first and second transparent, conductive sheets; and

a touch screen controller coupled to the first and the second conductive sheets, wherein the touch screen controller drives one of the first and second conductive sheets with an electrical signal referenced to the other of the first and second conductive sheets and measures capacitive current flow between the first and second conductive sheets; and

a display, disposed below the touch screen, for displaying information.

45. The touch screen display system of claim 44, wherein the display is a liquid crystal display, a light emitting diode display, a plasma display or a cathode ray tube display.

46. The touch screen display system of claim 44, wherein the controller is arranged to detect a touch made on the touch screen relative to information displayed on the display.

47. The touch screen display system of claim 44, further comprising a processor coupled to receive touch location information from the touch screen controller and to the display for controlling the information displayed on the display.

48. The system of claim 47, further comprising:

one or more data storage devices coupled to the processor for storing data; and

one or more inpuvoutput devices for transferring information to and from the controller.

49. The system of claim 44, further comprising circuitry for coupling the processor to a network.

50. The system of claim 44, wherein the touch screen controller is coupled to the first and second transparent, conductive sheets in a closed loop.

51. A system for sensing a location of a touch on a touch sensor, comprising:

means for sensing a change in capacitance between a first transparent, conductive sheet and a second transparent, conductive sheet when at least a portion of the first transparent, conductive sheet is moved towards the second transparent, conductive sheet; and

means for determining the two-dimensional location of the touch from signals derived from the change in capacitance between the two transparent conductive sheets.

52. A touch sensor comprising:

two transparent, electrically continuous conductive layers disposed in a touch area and defining a gap between the two layers;

wherein, a location of a touch input is determined by a change in capacitance between the two layers.

53. A touch sensor as recited in claim 52, wherein the change in capacitance occurs when the touch input locally flexes one conductive layer towards the other conductive layer.

54. A touch sensor as recited in claim 52, wherein the transparent, electrically continuous conductive layers are formed from a metal oxide.

55. A touch sensor as recited in claim 52, wherein the transparent, electrically continuous conductive layers are formed from a conductive polymer.

56. A touch sensor as recited in claim 52, further comprising a gap filler material disposed in the gap between the two transparent, electrically continuous conductive layers.

57. A touch sensor as recited in claim 52, further comprising spacers disposed in the gap between the two transparent, electrically continuous conductive layers.

58. A touch sensor as recited in claim 52, wherein the location of the touch input is a two dimensional location.

59. A touch sensor as recited in claim 52, further comprising a protective layer on a surface of at least one of the transparent, electrically continuous conductive layers facing the gap.

60. A touch sensor as recited in claim 52, further comprising a controller electrically coupled to the two transparent, electrically continuous conductive layers to determine the location of the touch.

61. A touch sensor as recited in claim 60, wherein the controller drives one of the transparent, electrically continuous conductive layers with an electrical signal referenced to the other of the transparent, electrically continuous conductive layers, and measures capacitive current flow between the transparent, electrically continuous conductive layers.

62. A touch sensor as recited in claim 52, further comprising a display unit disposed to display an image through the two transparent, electrically continuous conductive layers to a viewer.

63. A touch sensor as recited in claim 62, further comprising a processor coupled to the display unit to process information and direct information display signals to the display unit.