5-wire resistive touchscreens with metal electrodes
A touch sensor includes a resistive layer on a substrate and electrodes on the resistive layer. The electrodes and portions of the resistive layer between the electrodes form series resistor chains disposed at peripheral regions of the touch sensor and surrounding a touch region of the touch sensor. The electrodes are formed by forming a conductive layer on the resistive layer in a thin-film deposition process, followed by patterning the conductive layer into the electrodes. A sheet resistivity of the resistive layer is between about 200Ω and about 800Ω. A sheet resistivity of the conductive layer is between about 0.03Ω and about 0.2Ω. A ratio of the sheet resistivity of the resistive layer to the sheet resistivity of the conductive layer is between about 2,500 and about 10,000.
1. A touch sensor, comprising:
a resistive layer on a substrate, wherein a sheet resistivity of the resistive layer is between about 200Ω and about 800 Ω;
a touch region on the substrate; and
a peripheral region between the touch region and an edge of the substrate, wherein the peripheral region comprises:
a series resistor chain comprising a plurality of electrodes, wherein each of the plurality of electrodes comprises a conductive layer on the resistive layer, and wherein a sheet resistivity of the conductive layer is between about 0.03Ω and about 0.2Ω; and
an array of insulating regions between the series resistor chain and the touch region.
2. The touch sensor of claim 1 , wherein the sheet resistivity of the resistive layer is about 400 Ω.
3. The touch sensor of claim 1 , wherein the sheet resistivity of the conductive layer is about 0.08Ω.
4. The touch sensor of claim 1 , wherein a ratio of the sheet resistivity of the resistive layer to the sheet resistivity of the conductive layer is between about 2,500 and about 10,000.
5. The touch sensor of claim 1 , wherein a ratio of the sheet resistivity of the resistive layer to the sheet resistivity of the conductive layer is about 5,000.
6. The touch sensor of claim 1 , wherein the conductive layer comprises a sputtered metal.
7. The touch sensor of claim 1 , wherein the resistive layer comprises indium tin oxide.
8. The touch sensor of claim 1 , wherein the conductive layer comprises a metal layer, wherein the metal layer comprises aluminum, copper, silver, or a combination thereof.
9. The touch sensor of claim 8 , wherein the conductive layer further comprises an adhesive layer between the metal layer and the resistive layer, wherein the adhesive layer comprises molybdenum, titanium, chromium, or a combination thereof.
10. The touch sensor of claim 8 , wherein the conductive layer further comprises a capping layer on the metal layer, wherein the capping layer comprises molybdenum, chromium, platinum, gold, or a combination thereof.
11. A 5-wire resistive touchscreen, comprising:
a layer of indium tin oxide (ITO) on a transparent substrate, wherein a sheet resistivity of the layer of ITO is between about 360Ω and about 440Ω; and
a plurality of electrodes disposed adjacent to an edge of the layer of ITO, wherein the plurality of electrodes and portions of the layer of ITO between adjacent electrodes of the plurality of electrodes form a series resistor chain, and wherein a sheet resistivity of the plurality of electrodes is between about 0.06Ω and about 0.1Ω.
12. The 5-wire resistive touchscreen of claim 11 , wherein the sheet resistivity of the layer of ITO is about 400 Ω.
13. The 5-wire resistive touchscreen of claim 11 , wherein the sheet resistivity of the plurality of electrodes is about 0.08Ω.
14. The 5-wire resistive touchscreen of claim 11 , wherein a thickness of the plurality of electrodes is between about 100 nm and about 1 μm.
15. The 5-wire resistive touchscreen of claim 11 , wherein each of the plurality of electrodes comprises aluminum, copper, silver, titanium, molybdenum, or a combination thereof.
16. The 5-wire resistive touchscreen of claim 11 , wherein each of the plurality of electrodes comprises:
an adhesive layer on the layer of ITO;
a metal layer on the adhesive layer; and
a capping layer on the metal layer.
17. A method for forming a touchscreen, comprising:
forming a resistive layer on a transparent substrate;
removing portions of the resistive layer to form an array of insulating regions;
forming a conductive layer on the resistive layer, wherein forming the conductive layer comprises controlling a ratio of a sheet resistivity of the resistive layer to a sheet resistivity of the conductive layer to be between about 2,500 and about 10,000;
forming a resistor chain adjacent to the array of insulating regions by patterning the conductive layer to form a plurality of electrodes.
18. The method of claim 17 , wherein forming the conductive layer comprises depositing a metallic material by a sputter process, an evaporation process, an electroplating process, or a combination thereof.
19. The method of claim 17 , wherein controlling the ratio comprises controlling a thickness of the conductive layer.
20. The method of claim 17 , wherein forming the conductive layer comprises:
forming an adhesive layer on the resistive layer;
forming a metal layer on the adhesive layer; and
forming a capping layer on the metal layer.