Touch screen shield layer with ring and tapping points
Differential driving and/or sensing can reduce noise in a touch screen. In some examples, the touch electrodes and/or routing traces can be implemented using metal mesh in first and second metal layers. To mitigate electrical interference at the touch screen from a display, a display-noise shield or sensor can be provided between the display and the touch screen. In some examples, a shield can minimize a noise contribution from the display to signals generated at the touch screen. In other examples, a sensor can enable a differential read out of signals at the touch screen that subtracts a noise component measured by the sensor. Forming the shield or sensor, and the touch screen over the display using an on-cell process can improve touch screen performance and yield. The shield can be connected to a conductive ring and flex circuit via tapping points in a stackup separate from a display stackup.
1. A touch screen comprising:
a first substrate;
a plurality of display pixels disposed on the first substrate;
a first encapsulation layer formed over the plurality of display pixels, the plurality of display pixels between the first encapsulation layer and the first substrate;
one or more first electrodes formed in one or more metal layers disposed on the first encapsulation layer;
a touch sensor panel including one or more second electrodes formed in one or more layers; and
a dielectric layer disposed between the one or more first electrodes and the touch sensor panel.
2. The touch screen of claim 1 , wherein the one or more first electrodes comprise:
a display-noise shield between the plurality of display pixels and the touch sensor panel.
3. The touch screen of claim 2 , wherein the one or more metal layers on the first encapsulation layer comprise a metal mesh layer including metal mesh, and wherein:
the display-noise shield extends over the plurality of display pixels.
4. The touch screen of claim 3 , wherein the display-noise shield comprises:
indium tin oxide (ITO) deposited in openings of the metal mesh in the metal mesh layer.
5. The touch screen of claim 1 , wherein the one or more first electrodes comprise:
a display-noise sensor between the plurality of display pixels and the touch sensor panel, wherein the one or more metal layers on the first encapsulation layer comprise:
a first metal layer;
a second metal layer; and
an inter-layer dielectric layer between the first metal layer and the second metal layer.
6. The touch screen of claim 1 , wherein:
each of the one or more first electrodes corresponds to a respective one of the one or more second electrodes of the touch sensor panel.
7. The touch screen of claim 1 , wherein the one or more layers of the touch sensor panel comprise:
a first metal layer;
a second metal layer; and
an inter-layer dielectric layer between the first metal layer and the second metal layer, wherein the first metal layer and the second metal layer are both indium tin oxide (ITO) layers.
8. The touch screen of claim 1 , the one or more first electrodes forming a shield layer, the touch screen further comprising:
a conductive ring formed on and electrically connected to the shield layer along at least a portion of a perimeter of the shield layer, the conductive ring formed from a lower resistance material than the shield layer; and
a flex circuit including
one or more tabs having a plurality of first conductive traces electrically coupled to the touch sensor panel, and
one or more flex circuit wings having one or more second conductive traces electrically coupled to the conductive ring at one or more tapping points disposed along the conductive ring.
9. The touch screen of claim 8 , further comprising:
a plurality of tapping points disposed along the conductive ring, the plurality of tapping points electrically couplable to a touch ground through one or more of the second conductive traces in the flex circuit;
wherein the plurality of tapping points connect the shield layer to the touch ground in a parallel configuration to reduce a resistance between the shield layer and the touch ground.
10. The touch screen of claim 9 , wherein the conductive ring is formed with corners corresponding to corners of the shield layer, and the plurality of tapping points are located in at least two corners of the conductive ring located closest to the flex circuit.
11. The touch screen of claim 8 , wherein the shield layer is formed from a transparent metal including one of Indium Tin Oxide (ITO), silver nanowire (AgNW) or silver Indium Tin Oxide (AgITO).
12. The touch screen of claim 11 , wherein the shield layer includes a metal mesh disposed on the transparent metal.
13. The touch screen of claim 11 , wherein the shield layer includes the transparent metal formed over a metal mesh.
14. The touch screen of claim 11 , wherein the shield layer includes a metal mesh disposed on gaps between patches of the transparent metal.
15. The touch screen of claim 14 , where the gaps between the patches of the transparent metal are oriented parallel to a bending axis of the touch screen.
16. A touch sensing stackup, comprising:
a first substrate;
a shield layer disposed on the first substrate;
a conductive ring formed on and electrically connected to the shield layer along at least a portion of a perimeter of the shield layer, the conductive ring formed from a lower resistance material than the shield layer;
a touch sensor panel disposed over the first substrate, the touch sensor panel including one or more touch electrodes formed in one or more conductive layers; and
a flex circuit including
one or more tabs having a plurality of first conductive traces electrically coupled to the touch sensor panel, and
one or more flex circuit wings having one or more second conductive traces electrically coupled to the conductive ring at one or more tapping points disposed along the conductive ring.
17. The touch sensing stackup of claim 16 , further comprising:
a plurality of tapping points disposed along the conductive ring, the plurality of tapping points electrically couplable to a touch ground through one or more of the second conductive traces in the flex circuit;
wherein the plurality of tapping points connect the shield layer to the touch ground in a parallel configuration to reduce a resistance between the shield layer and the touch ground.
18. The touch sensing stackup of claim 17 , wherein the conductive ring is formed with corners corresponding to corners of the shield layer, and the plurality of tapping points are located in at least two corners of the conductive ring located closest to the flex circuit.
19. The touch sensing stackup of claim 16 , wherein the conductive ring is formed in a continuously connected loop along the perimeter of the shield layer.
20. The touch sensing stackup of claim 16 , wherein the conductive ring is formed in a discontinuously connected loop along the perimeter of the shield layer.
21. The touch sensing stackup of claim 16 , wherein the shield layer is formed from a transparent metal.
22. The touch sensing stackup of claim 21 , wherein the shield layer includes a metal mesh disposed on the transparent metal.
23. The touch sensing stackup of claim 21 , wherein the shield layer includes the transparent metal formed over a metal mesh.
24. The touch sensing stackup of claim 21 , wherein the shield layer includes a metal mesh disposed on gaps between patches of the transparent metal.
25. The touch sensing stackup of claim 24 , wherein the gaps between the patches of the transparent metal are oriented parallel to a bending axis of the touch sensing stackup.