Printed Force Sensor Within A Touch Screen

• US 20110037721A1
• Filed: 08/12/2009
• Published: 02/17/2011
• Est. Priority Date: 08/12/2009
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Inventors: Cranfill, David, Parikh, Zubin
• Granted Patent: US 9,430,078 B2
• Time in Patent Office: Days
• 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
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A quantum tunneling composite, or other material exhibiting changing electrical or magnetic properties as force on the material is increased, can be located within a force concentrator integrated into traditional touch screen layers to sense force applied on the touch screen. The force concentrator can be a protrusion from the layer planes of the layers in a traditional touch screen and can be formed, at least in part, from printed elements. The amount of protrusion of the force concentrator can be adjusted through multi-pass printing and thicker deposit printing. The force concentrator can also have optically clear adhesive layered over it. The force-sensitive material can be optionally pre-loaded so as to operate within a substantially linear feedback range. A sensing mechanism can be configured to detect changes in force at multiple locations or to detect the application of force irrespective of location.

Claims

1. A force sensor integrated into a multi-layer touch screen, the force sensor comprising:

a variably conductive material whose conductivity changes in accordance with an amount of compressive force applied to the variably conductive material;

a first electrode positioned on a first side of the variable conductive material and between the variably conductive material and a first layer of the multi-layer touch screen; and

a second electrode positioned on a second side of the variably conductive material opposite the first side of the variably conductive material and between the variably conductive material and a second layer of the multi-layer touch screen that is substantially parallel to the first layer;

wherein the variably conductive material, the first electrode, and the second electrode form a protrusion from a layer plane of the second layer, the protrusion extending towards the first layer.

2. The force sensor of claim 1, wherein an optically clear adhesive between the first layer of the multi-layer touch screen and the second layer of the multi-layer touch screen is also layered over the first electrode, the variably conductive material and the second electrode;

and wherein further the protrusion from the layer plane of the second layer extending towards the first layer is further formed from the optically clear adhesive layered over the first electrode, the variably conductive material, and the second electrode.

3. The force sensor of claim 1, wherein the first electrode is conductively connected to another first electrode of another force sensor and wherein the second electrode is conductively connected to another second electrode of the other force sensor.

4. The force sensor of claim 1, wherein a space between the first layer of the multi-layer touch screen and the second layer of the multi-layer touch screen is smaller than a rest state thickness of the variably conductive material in combination with a thickness of the first and second electrodes.

5. The force sensor of claim 1, wherein the variably conductive material is a quantum tunneling composite.

6. The force sensor of claim 1, wherein the multi-layer touch screen is a mutual-capacitance-based touch screen with the first layer comprising a first set of electrodes and the second layer comprising a second set of electrodes intersecting the first set of electrodes such that each intersection forms a capacitive element of the mutual-capacitance based touch screen.

7. The force sensor of claim 1, wherein the force sensor is integrated into the multi-layer touch screen at the periphery of the multi-layer touch screen.

8. The force sensor of claim 1, wherein the protrusion concentrates, onto the variably conductive material, a force applied to at least one of the first layer and the second layer, thereby effecting the variably conductive material'"'"'s conductive coupling of the first electrode to the second electrode.

9. A method of manufacturing a multi-layer touch screen with at least one integrated force sensor comprising the steps of:

depositing a first electrode on a first layer of the multi-layer touch screen;

depositing, on top of at least a portion of the first electrode, a variably conductive material whose conductivity changes in accordance with an amount of compressive force applied to the variably conductive material;

depositing a second electrode on top of at least a portion of the variably conductive material such that at least a portion of the second electrode is on an opposite side of the variably conductive material from the first electrode; and

layering a second layer of the multi-layer touch screen on top of the second electrode.

10. The method of claim 9, further comprising the step of layering an optically clear adhesive over at least a portion of the first layer of the multi-layer touch screen and over at least a portion of the first electrode, the variably conductive material, and the second electrode such that the optically clear adhesive is between the at least the portion of the first layer and the second layer of the multi-layer touch screen and such that the optically clear adhesive is also between the second layer and the at least a portion of the first electrode, the variably conductive material, and the second electrode.

11. The method of claim 9, further comprising the step of applying pressure onto the second layer of the multi-layer touch screen so as to finalize manufacturing of the multi-layer touch screen with the variably conductive material compressed beyond a rest state.

12. The method of claim 9, wherein the variably conductive material is a quantum tunneling composite.

13. The method of claim 9, wherein the depositing the first electrode on the first layer comprises depositing the first electrode on the first layer near a periphery of the first layer.

14. An electronic device capable of distinguishing between touch input and press input, the electronic device comprising:

touch detection circuitry for identifying the touch input;

press detection circuitry for identifying the press input; and

a multi-layer touch screen for receiving the touch input, the multi-layer touch screen comprising a first layer, a second layer that is substantially parallel to the first layer, and at least one integrated force sensor for receiving the press input, the at least one integrated force sensor being located between the first layer and the second layer and forming a protrusion from a layer plane of the second layer extending towards the first layer, the at least one integrated force sensor comprising;

a variably conductive material whose conductivity changes in accordance with an amount of compressive force applied to the variably conductive material;

a first electrode positioned on a first side of the variably conductive material and between the variably conductive material and the first layer of the multi-layer touch screen; and

a second electrode positioned on a second side of the variably conductive material opposite the first side of the variably conductive material and between the variably conductive material and the second layer of the multi-layer touch screen.

15. The electronic device of claim 14, wherein the press input provides a force onto at least one of the first layer and the second layer, the provided force being concentrated, by the protrusion of the at least one integrated force sensor, onto the variably conductive material and thereby effecting the variably conductive material'"'"'s conductive coupling of the first electrode to the second electrode;

and wherein further the effect to the conductive coupling is detectable by the press detection circuitry.

16. The electronic device of claim 14, wherein the multi-layer touch screen further comprises an optically clear adhesive layered over the second layer and the at least one integrated force sensor such that the optically clear adhesive is between the first layer and the second layer and between the first layer and the at least one integrated force sensor.

17. The electronic device of claim 14, wherein the multi-layer touch screen further comprises at least two integrated force sensors, wherein a first electrode of a first of the at least two integrated force sensors is conductively connected to a first electrode of a second of the at least two integrated force sensors and a second electrode of the first of the at least two integrated force sensors is conductively connected to a second electrode of the second of the at least two integrated force sensors, and wherein further the press detection circuitry identifies the press input by detecting a change in a combined conductivity of the at least two integrated force sensors.

18. The electronic device of claim 14, wherein the multi-layer touch screen further comprises at least two integrated force sensors, wherein a first electrode of a first of the at least two integrated force sensors is conductively connected to the press detection circuitry separately from a first electrode of a second of the at least two integrated force sensors that is also conductively connected to the press detection circuitry, and wherein further the press detection circuitry identifies the press input by detecting a change in an individual conductivity of at least one of the at least two integrated force sensors.

19. The electronic device of claim 18, wherein the press detection circuitry comprises a time sampling microcontroller to detect the change in the individual conductivity of at least one of the at least two integrated force sensors.

20. The electronic device of claim 14, wherein a space between the first layer of the multi-layer touch screen and the second layer of the multi-layer touch screen is smaller than a rest state thickness of the variably conductive material in combination with a thickness of the first and second electrodes.