Apparatus and method for a multilayer pixel structure
The present disclosure provides a pixel structure comprising a plurality of layers for providing a touch sensitive pixel of a sensing array. The layers comprising: a thin film transistor; and a conductive layer deposited on a dielectric shield to be touched by an object to be sensed and arranged to provide a capacitive sensing electrode coupled to the thin film transistor. The present disclosure also provides methods of manufacturing such a pixel structure.
1. A pixel structure comprising a plurality of layers for providing a touch sensitive pixel of a sensing array, the pixel comprising:
a sense thin film transistor (TFT);
a select TFT coupled to the sense TFT; and
a capacitive sensing electrode coupled to the sense TFT;
wherein each TFT comprises: (i) a gate layer comprising a gate region of the TFT, (ii) a source-drain layer comprising a source region and a drain region of the TFT, and (iii) a channel region which connects the source region and the drain region to provide a conduction path therebetween when the TFT is in an on state;
wherein the pixel structure comprises a conductive layer arranged to provide the capacitive sensing electrode;
wherein a gate layer of the sense TFT is connected to the capacitive sensing electrode;
wherein the conduction path of the sense TFT is connected to the conduction path of the select TFT; and
wherein the conduction path of the sense TFT is connected between: (i) the conduction path of the select TFT, and (ii) a read-out line for the pixel.
2. The pixel structure of claim 1 , wherein the conduction path of the select TFT is connected in series between the conduction path of the sense TFT and a reference signal supply.
3. The pixel structure of claim 2 , wherein when the pixel is not active, the select TFT is in an off state and the conduction path of the sense TFT is disconnected from the reference signal supply.
4. The pixel structure of claim 1 , wherein the gate layer of the select TFT is connected to receive a control voltage for switching the select TFT into its on state.
5. The pixel structure of claim 1 , wherein the gate layer of the select TFT is connected to a gate drive line for that pixel.
6. The pixel structure of claim 1 , wherein the source-drain layer of the sense TFT is connected to the source-drain layer of the select TFT.
7. The pixel structure of claim 1 , wherein the pixel comprises a reference capacitor comprising a first plate and a second plate, wherein the gate layer of the sense TFT is connected to the second plate of the reference capacitor.
8. The pixel structure of claim 7 , wherein the first plate of the reference capacitor is connected to a gate drive channel line for that pixel.
9. The pixel structure of claim 1 , wherein the pixel comprises a reference capacitor and wherein one plate of the reference capacitor is provided by a source-drain layer or a gate layer of the pixel.
10. The pixel structure of claim 1 , wherein the pixel comprises a reference capacitor, and wherein the reference capacitor is connected to a gate line for the pixel for activating the pixel.
11. The pixel structure of claim 1 , wherein the conduction path of the sense TFT is connected to an input channel of a read-out circuit.
12. The pixel structure of claim 1 , wherein the pixel comprises a reset TFT coupled to the sense TFT, wherein the reset TFT comprises: (i) a gate layer comprising a gate region of the reset TFT, (ii) a source-drain layer comprising a source region and a drain region of the reset TFT, and (iii) a channel region which connects the source region and the drain region to provide a conduction path therebetween when the TFT is in an on state; and
wherein the conduction path of the reset TFT is connected to the gate layer of the sense TFT.
13. The pixel structure of claim 12 , wherein the gate layer of the reset TFT is connected to a control voltage for switching the conduction path of the reset TFT into its on state.
14. A pixel structure comprising a plurality of layers for providing a touch sensitive pixel of a sensing array, the pixel comprising:
a sense thin film transistor (TFT);
a reset TFT coupled to the sense TFT; and
a capacitive sensing electrode coupled to the sense TFT;
wherein each TFT comprises: (i) a gate layer comprising a gate region of the TFT, (ii) a source-drain layer comprising a source region and a drain region of the TFT, and (iii) a channel region which connects the source region and the drain region to provide a conduction path therebetween when the TFT is in an on state;
wherein the pixel structure comprises a conductive layer arranged to provide the capacitive sensing electrode;
wherein the gate layer of the sense TFT is connected to the capacitive sensing electrode and the conduction path of the reset TFT; and
wherein the conductive path of the reset TFT is connected between a reset voltage provider and the gate region of the sense TFT, and wherein the reset voltage provider is configured to reset the voltage at the gate region of the sense TFT to a reset voltage value selected to provide a selected pixel sensitivity.
15. The pixel structure of claim 14 , wherein the pixel comprises a reference capacitor comprising a first plate and a second plate, and wherein the gate layer of the sense TFT is connected to both the second plate of the reference capacitor and the conduction path of the reset TFT.
16. The pixel structure of claim 14 , wherein the source-drain layer of the reset TFT is connected to the gate layer of the sense TFT.
17. A pixel structure comprising a plurality of layers for providing a touch sensitive pixel of a sensing array, the pixel comprising:
a sense thin film transistor (TFT);
a reference capacitor comprising a first plate and a second plate, wherein the reference capacitor is coupled to the sense TFT; and
a capacitive sensing electrode coupled to the sense TFT;
wherein the sense TFT comprises: (i) a gate layer comprising a gate region of the TFT, (ii) a source-drain layer comprising a source region and a drain region of the TFT, and (iii) a channel region which connects the source region and the drain region to provide a conduction path therebetween when the TFT is in an on state;
wherein the pixel structure comprises a conductive layer arranged to provide the capacitive sensing electrode;
wherein the gate layer of the sense TFT is connected to the capacitive sensing electrode and the second plate of the reference capacitor; and
wherein one of the plates of the reference capacitor is provided in the same layer which provides the gate layer of the sense TFT, and the other of the plates of the reference capacitor is provided in the same layer which provides the source-drain layer of the sense TFT.
18. The pixel structure of claim 17 , wherein the first plate of the reference capacitor is connected to a gate line for the pixel.