TOUCH CELL STRUCTURE OF A TOUCH PANEL AND THE TOUCH PANEL USING THE SAME

• US 20120319992A1
• Filed: 12/17/2010
• Published: 12/20/2012
• Est. Priority Date: 12/17/2009
• Status: Active Grant

• Current Assignee: G2touch Co Ltd
• Original Assignee: G2touch Co Ltd
• Inventors: Lee, Sung Ho
• Granted Patent: US 9,785,290 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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

Provided is a touch cell structure for a touch panel in which a touch cell is configured into a new pad to gate mode in order to solve a problem of a conventional capacitive-type touch input device. The touch cell structure includes: a conductive pad that forms an electrostatic capacitance with respect to a touch unit when a finger of a human body or the touch unit having an electrical characteristic similar to the finger approaches the conductive pad within a predetermined distance; and a three-terminal type switching device whose gate terminal is connected with the conductive pad and whose output signal is changed in correspondence to a change in electric potential of the gate terminal of the three-terminal type switching device by the electrostatic capacitance between the touch unit and the conductive pad. Since the potential of the gate terminal of the switching device is determined by an electrostatic capacitance formed in the conductive pad, a difference of the output signal output from the switching device becomes large depending on whether a touch input occurs or not.

Claims

1. A touch cell structure constituting a unit touch cell in a touch panel, the touch cell structure comprising:

a conductive pad that forms an electrostatic capacitance with respect to a touch unit when a finger of a human body or the touch unit having an electrical characteristic similar to the finger approaches the conductive pad within a predetermined distance; and

a three-terminal type switching device whose gate terminal is connected with the conductive pad and whose output signal is changed in correspondence to a change in electric potential of the gate terminal of the three-terminal type switching device by the electrostatic capacitance between the touch unit and the conductive pad.

2. The touch cell structure according to claim 1, wherein the switching device comprises:

a first three-terminal type switching unit whose output signal is connected with the conductive pad, and that is turned on/off according to a control signal applied to a gate terminal of the first three-terminal type switching unit, to thereby supply a charging signal to the conductive pad; and

a second three-terminal type switching unit whose gate terminal is connected with the conductive pad and whose output signal is changed in correspondence to a change in electric potential of the gate terminal of the three-terminal type switching unit.

3. The touch cell structure according to claim 2, wherein the touch cell structure further comprises capacitors that are connected between the control terminal and the output terminal of the first three-terminal type switching unit and the second three-terminal type switching unit, respectively.

4. The touch cell structure according to claim 3 wherein the capacitor connected between the control terminal and output terminal of the first three-terminal type switching unit is in the range of 10 fF to 100 uF.

5. The touch cell structure according to claim 3, wherein the capacitor connected between the control terminal and the output terminal of the first three-terminal type switching unit is selected to have a smaller value by twice to several hundreds of times than a value of a capacitor formed between the touch unit and the touch pad.

6. The touch cell structure according to claim 3, wherein the capacitor connected between the control terminal and the output terminal of the first three-terminal type switching unit is selected to have a value or more of a capacitor formed between the touch unit and the touch pad.

7. The touch cell structure according to claim 3, wherein the capacitors are built in the first three-terminal type switching unit and the second three-terminal type switching unit, respectively.

8. The touch cell structure according to claim 3, wherein the capacitors are provided in the outside of the first three-terminal type switching unit and the second three-terminal type switching unit, respectively.

9. The touch cell structure according to claim 3, wherein the touch cell structure further comprises a capacitor connected between the input terminal and control terminal of the second three-terminal type switching unit.

10. The touch cell structure according to claim 1, wherein the touch cell structure further comprises an auxiliary capacitor between the conductive pad and the ground.

11. The touch cell structure according to claim 1, wherein the switching device is any one selected from the group consisting of a relay, a MOS (Metal Oxide Semiconductor) switch, a BJT (Bipolar Junction Transistor) switch, a FET (Field Effect Transistor) switch, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) switch, an IGBT (Insulated Gate Bipolar Transistor) switch, and a TFT (Thin Film Transistor) switch.

12. A touch panel comprising:

a light transmissive substrate;

touch cells that are arranged in a matrix form on the light transmissive substrate, in which each touch cell comprises a conductive pad, and a three-terminal type switching device whose gate terminal is connected with the conductive pad and whose output signal is changed in correspondence to a change in electric potential of the gate terminal of the three-terminal type switching device by an electrostatic capacitance between a finger of a human body or a touch unit having an electrical characteristic similar to the finger and the conductive pad; and

a touch position detector that recognizes a touch input from the output of the switching device.

13. The touch panel according to claim 12, wherein the switching device comprises:

a first three-terminal type switching unit whose output signal is connected with the conductive pad, and that is turned on/off according to a control signal applied to a gate terminal of the first three-terminal type switching unit, to thereby supply a charging signal to the conductive pad; and

a second three-terminal type switching unit whose gate terminal is connected with the conductive pad and whose output signal is changed in correspondence to a change in electric potential of the gate terminal of the three-terminal type switching unit.

14. The touch panel according to claim 13, further comprising capacitors that are connected between the control terminal and the output terminal of the first three-terminal type switching unit and the second three-terminal type switching unit, respectively.

15. The touch panel according to claim 14, wherein the capacitor connected between the control terminal and output terminal of the first three-terminal type switching unit is in the range of 10 fF to 100 uF.

16. The touch panel according to claim 14, wherein the capacitor connected between the control terminal and the output terminal of the first three-terminal type switching unit is selected to have a smaller value by twice to several hundreds of times than a value of a capacitor formed between the touch unit and the touch pad.

17. The touch panel according to claim 14, wherein the capacitor connected between the control terminal and the output terminal of the first three-terminal type switching unit is selected to have a value or more of a capacitor formed between the touch unit and the touch pad.

18. The touch panel according to claim 14, wherein the capacitors are built in the first three-terminal type switching unit and the second three-terminal type switching unit, respectively.

19. The touch panel according to claim 14, wherein the capacitors are provided in the outside of the first three-terminal type switching unit and the second three-terminal type switching unit, respectively.

20. The touch panel according to claim 14, further comprising a capacitor connected between the input terminal and control terminal of the second three-terminal type switching unit.

21. The touch panel according to claim 20, further comprising an auxiliary capacitor between the conductive pad and the ground.

22. The touch panel according to claim 13, wherein the switching device is any one selected from the group consisting of a relay, a MOS (Metal Oxide Semiconductor) switch, a BJT (Bipolar Junction Transistor) switch, a FET (Field Effect Transistor) switch, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) switch, an IGBT (Insulated Gate Bipolar Transistor) switch, and a TFT (Thin Film Transistor) switch.

23. The touch panel according to claim 13, wherein the touch position detector applies an on/off control signal to a control terminal of the first switching unit, applies a position detection signal to an input terminal thereof, and compares a difference of an output signal of the second switching unit according to a difference of a kick back depending upon whether or not a touch input exists, to thus recognize the touch input.

24. The touch panel according to claim 23, wherein the output signal of the second switching unit has tens of times or tens of thousands of times a difference depending upon whether or not a touch input exists.

25. The touch panel according to claim 23, further comprising a comparator for comparing the output signal of the second switching unit and a reference signal.

26. The touch panel according to claim 25, wherein a sensing cell 61 including a three-terminal sensing switching unit 64, which has the same circuit configuration as the second switching unit 44 but to the control terminal of which the conductive pad 50 is not connected, is further provided at one side of the substrate 30, the touch position detector 70 applies a control signal corresponding to a value positioned between a signal applied to the control terminal of a second TFT 44 of the touch cell 60 at the time of no occurrence of touch inputs and a signal applied to the control terminal of the second TFT 44 of the touch cell 60 at the time of occurrence of touch inputs, to the control terminal of the sensing switching unit 64, the same signal as the signal applied to the input terminal of the second TFT 44 is applied to the input terminal of the sensing switching unit 64, and the signal output from the output terminal of the sensing switching unit 64 is used as a reference signal of the comparator.

27. The touch panel according to claim 12, wherein the touch position detector further comprises a memory unit having addresses corresponding to the coordinates of the touch cell, in which if a touch input is detected, coordinate values of the corresponding touch cell are stored in the corresponding addresses of the memory unit.