Capacitive coupling for PCAP touchscreens with varying ITO dicing patterns
Embodiments include a method and system for projected capacitive (PCAP) touchscreen construction with laser ablation. In glass/film/film (GFF) PCAP touchscreens, the films are coated with indium-tin-oxide (ITO), patterned by printing silver ink, and by ablating both the ITO and silver with a laser. A similar process occurs for a glass/glass (2GS) PCAP touchscreen. Embodiments include varying the pattern with which the laser ablates ITO on film within the touch area to improve touchscreen sensitivity. For example, by varying the width of patterns of floating ITO islands such that widths are less than or equal to a plan-view electrode gap between vertical and horizontal electrode pads and larger elsewhere, the touch sensitivity of the PCAP touchscreen may be improved and/or maximum touchscreen size may be increased.
1. A projected capacitive (PCAP) touchscreen, comprising:
a first transparent electrode comprising a vertical electrode pad and a first floating indium-tin-oxide (ITO) island;
a second transparent electrode parallel to the first transparent electrode, comprising a horizontal electrode pad,
wherein the vertical electrode pad is separated from the horizontal electrode pad by a plan-view electrode gap, and wherein a dimension of the first floating ITO island is less than or equal to the plan-view electrode gap, and
wherein the dimension of the first floating ITO island is based on a varying ITO dicing pattern, and a first signal path from the vertical electrode pad to the horizontal electrode pad via the first floating ITO island comprises at least one high-impedance edge-to-edge capacitance or one high-impedance small-area capacitance.
2. The PCAP touchscreen of claim 1 , wherein the first signal path has a higher impedance than a second signal path from the vertical electrode pad to the horizontal electrode pad via a second floating ITO island of the first transparent electrode, and wherein the second floating ITO island is based on a uniform ITO dicing pattern.
3. The PCAP touchscreen of claim 1 , wherein the first floating ITO island is centered within the plan-view electrode gap.
4. The PCAP touchscreen of claim 1 , wherein the second transparent electrode further comprises a second floating ITO island, and wherein the first floating ITO island and the second floating ITO island are not aligned within the plan-view electrode gap.
5. The PCAP touchscreen of claim 1 , wherein the first floating ITO island is smaller than one or more floating ITO islands of the first transparent electrode.
6. The PCAP touchscreen of claim 5 , wherein the one or more floating ITO islands of the first transparent electrode vary in length.
7. The PCAP touchscreen of claim 5 , wherein the one or more floating ITO islands of the first transparent electrode are substantially equivalent in length.
8. The PCAP touchscreen of claim 1 , wherein the varying ITO dicing pattern causes a reduction in a value of mutual capacitance, C M , between the vertical electrode pad and the horizontal electrode pad.
9. The PCAP touchscreen of claim 8 , wherein the varying ITO dicing pattern causes a reduction in an RC settling time of the PCAP touchscreen and an increase in touch sensitivity, ΔC M /C M .
10. The PCAP touchscreen of claim 1 , wherein the second transparent electrode further comprises a second floating ITO island, and wherein the first floating ITO island and the second floating ITO island are aligned within the plan-view electrode gap.
11. The PCAP touchscreen of claim 10 , wherein the first signal path from the vertical electrode pad to the horizontal electrode pad via the first floating ITO island further comprises a second high-impedance edge-to-edge capacitance.
12. A method for fabricating a projected capacitive (PCAP) touchscreen, comprising:
disposing on a first layer, a first transparent electrode comprising a vertical electrode pad and a first floating indium-tin-oxide (ITO) island on the first transparent electrode;
disposing on a second layer, a second transparent electrode parallel to the first transparent electrode, comprising a horizontal electrode pad, wherein the vertical electrode pad is separated from the horizontal electrode pad by a plan-view electrode gap, and wherein a dimension of the first floating ITO island is less than or equal to the plan-view electrode gap, and wherein the dimension of the first floating ITO island is based on a varying ITO dicing pattern; and
creating a first signal path from the vertical electrode pad to the horizontal electrode pad via the first floating ITO island, wherein the first signal path comprises at least one high-impedance edge-to-edge capacitance or one high-impedance small-area capacitance.
13. The method for fabricating the PCAP touchscreen of claim 12 , wherein the first signal path has a higher impedance than a second signal path from the vertical electrode pad to the horizontal electrode pad via a second floating ITO island of the first transparent electrode, and wherein the second floating ITO island is based on a uniform ITO dicing pattern.
14. The method for fabricating the PCAP touchscreen of claim 12 , wherein the first floating ITO island is centered within the plan-view electrode gap.
15. The method for fabricating the PCAP touchscreen of claim 12 , wherein the second transparent electrode further comprises a second floating ITO island, and wherein the first floating ITO island and the second floating ITO island are not aligned within the plan-view electrode gap.
16. The method for fabricating the PCAP touchscreen of claim 12 , wherein the first floating ITO island is smaller than one or more floating ITO islands of the first transparent electrode.
17. The method for fabricating the PCAP touchscreen of claim 16 , wherein the one or more floating ITO islands of the first transparent electrode vary in length.
18. The method for fabricating the PCAP touchscreen of claim 16 , wherein the one or more floating ITO islands of the first transparent electrode are substantially equivalent in length.
19. The method for fabricating the PCAP touchscreen of claim 12 , wherein the varying ITO dicing pattern causes a reduction in a value of mutual capacitance, C M , between the vertical electrode pad and the horizontal electrode pad.
20. The method for fabricating the PCAP touchscreen of claim 12 , wherein the varying ITO dicing pattern causes a reduction in an RC settling time of the PCAP touchscreen and an increase in touch sensitivity, ΔC M /C M .