Pressure activated switch and touch panel

• US 20030205450A1
• Filed: 05/02/2002
• Published: 11/06/2003
• Est. Priority Date: 05/02/2002
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Livingstone, David E., Cross, Elisa M., Divigalpitiya, Ranjith, Moshrefzadeh, Robert S.
• Granted Patent: US 6,809,280 B2
• Time in Patent Office: Days
• US Class Current: 200/512
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• 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 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact
• CPC Class Codes: H01H 1/029 comprising conducting material dispersed in an elastic support or binding material

Abstract

The present invention provides a switchable pressure activated electronic device. The switchable electronic device includes a composite material disposed between two conductors. The composite material electrically connects the two conductors when pressure is applied between them, and electrically isolates the two conductors when pressure is not applied between them. The composite includes conductive particles at least partially embedded in an insulating material. The conductive particles are disposed so that substantially all electrical connections made between the first and second conductors are through single particles.

Claims

1. A switchable pressure activated electronic device comprising:

a first conductor that is movable toward a second conductor; and

a composite material disposed between the first and second conductors for electrically connecting the first and second conductors under application of sufficient pressure therebetween and for electrically isolating the first and second conductors in the absence of such sufficient pressure,

the composite material comprising a plurality of conductive particles at least partially embedded in an electrically insulating layer,

the plurality of conductive particles having no intended relative orientation and being disposed so that substantially all electrical connections made between the first and second conductors are through single particles.

2. The device of claim 1, wherein the switchable pressure activated electronic device comprises a membrane switch.

3. The device of claim 1, wherein the switchable pressure activated electronic device comprises an array of membrane switches, each of said membrane switches being independently activatable.

4. The device of claim 1, wherein the switchable pressure activated electronic device comprises a touch sensor.

5. The device of claim 1, wherein the first and second conductors comprise sheets or coatings of conductive material.

6. The device of claim 5, wherein the first and second conductors are disposed on first and second substrates, respectively.

7. The device of claim 6, wherein at least one of the first and second substrates is flexible.

8. The device of claim 6, wherein at least one of the first and second substrates is rigid.

9. The device of claim 6, wherein at least one of the first and second substrates is transparent.

10. The device of claim 5, wherein the first and second conductors are transparent.

11. The device of claim 1, wherein at least one of the first and second conductors comprises a transparent conductive oxide.

12. The device of claim 1, wherein at least one of the first and second conductors comprises a metal.

13. The device of claim 1, wherein at least one of the first and second conductors comprises an organic conductor.

14. The device of claim 1, wherein at least one of the first and second conductors is patterned.

15. The device of claim 1, wherein at least one of the first and second conductors comprises a circuit.

16. The device of claim 1, wherein the composite material is disposed between the first and second conductors so that substantially no air gaps exist between the first and second conductors.

17. The device of claim 1, wherein the electrically insulating layer is transparent to visible light.

18. The device of claim 1, wherein the electrically insulating layer comprises an elastomeric material.

19. The device of claim 1, wherein the electrically insulating layer comprises a silicone material.

20. The device of claim 1, wherein the conductive particles are substantially spherical.

21. The device of claim 1, wherein the conductive particles comprise a metal.

22. The device of claim 1, wherein the conductive particles comprise core particles having a conductive coating.

23. The device of claim 22, wherein the conductive coating comprises a metal.

24. The device of claim 22, wherein the conductive coating comprises a transparent conductive oxide.

25. The device of claim 22, wherein the conductive coating comprises an organic conductor.

26. The device of claim 22, wherein the core particles comprise glass particles.

27. The device of claim 22, wherein the core particles comprise hollow particles.

28. The device of claim 1, wherein the conductive particles are transparent.

29. The device of claim 1, wherein the conductive particles are semi-transparent.

30. The device of claim 1, wherein the conductive particles are colored.

31. The device of claim 1, wherein the conductive particles are opaque.

32. The device of claim 1, wherein the conductive particles are deformable.

33. The device of claim 1, wherein the conductive particles are substantially the same size.

34. The device of claim 1, wherein the conductive particles exhibit a bi-modal size distribution.

35. The device of claim 1, wherein the first conductor comprises a conductive stylus.

36. The device of claim 1, further comprising graphics or indicia.

37. The device of claim 1, further comprising a display element viewable through the conductors and composite material.

38. A switchable pressure activated electronic device comprising:

a composite layer comprising a plurality of substantially spherical conductive particles disposed so that substantially none of the conductive particles are in mutual physical contact, and wherein, for substantially all positions across the layer, there is at most a single particle through the thickness of the layer,

the composite layer being disposed between two conductors and having a thickness that reversibly decreases upon application and cessation of sufficient force applied between the conductors to allow electrical connection of the conductors through one or more of the conductive particles during application of sufficient force and to allow electrical isolation of the conductors during cessation of sufficient force.

39. A method of making a switchable pressure activated electronic device comprising:

dispersing a plurality of conductive particles;

at least partially embedding the conductive particles in a layer of insulating material; and

disposing the layer of insulating material and conductive particles between a first conductor and a second conductor so that the first and second conductors are electrically connected through one or more single particle contacts upon application of sufficient pressure, and the first and second conductors are electrically isolated upon cessation of sufficient pressure.

40. The method of claim 39, wherein the step of dispersing the plurality of conductive particles comprises charging the particles so that the particles mutually repel and dispensing the particles on a surface.

41. The method of claim 40, wherein the surface is a surface of the layer of insulating material.

42. The method of claim 39, wherein at least partially embedding the conductive particles in the layer of insulating material comprises pressing the conductive particles into the layer of insulating material.

43. The method of claim 39, wherein at least partially embedding the conductive particles in the layer of insulating material comprises heating the layer of insulating material to allow the conductive particles to sink into a surface of the layer of insulating material.

44. The method of claim 39, wherein the steps of dispersing the conductive particles and embedding the conductive particles in a layer of the insulating material comprises dispersing the conductive particles in a liquid precursor of the insulating material to form a coatable composite, coating the coatable composite to form a composite layer, and hardening the liquid precursor to form the insulating layer having the conductive particles dispersed therein.

45. A film for use in an electronic switch, the film comprising a layer having a thickness that reversibly decreases with pressure, and a plurality of randomly positioned conductive particles at least partially embedded in said layer, wherein, for substantially all positions across the layer, there is at most a single particle through the thickness of the layer.

46. An electronic switch comprising:

a first conductor that is movable toward a second conductor; and

a plurality of substantially randomly positioned conductive particles disposed between the first and second conductors, the first conductor being electrically isolated from the second conductor in the absence of sufficient pressure therebetween, and the first conductor in electrical contact with the second conductor through one or more single particle connections when sufficient pressure is applied therebetween.

47. A display system comprising:

a display viewable through an electronic switch that comprises a first conductor that is movable toward a second conductor, and a plurality of substantially randomly positioned conductive particles disposed between the first and second conductors, the first conductor being electrically isolated from the second conductor in the absence of sufficient pressure therebetween, and the first conductor in electrical contact with the second conductor through one or more single particle connections when sufficient pressure is applied therebetween.

48. A switchable pressure activated electronic device comprising:

a first conductor;

a second conductor;

means for electrically connecting the first conductor to the second conductor upon application of sufficient pressure; and

means for electrically isolating the first conductor from the second conductor upon cessation of sufficient pressure.