Why do you need a conductive layer with conductivity of \$~10^4\$ S/cm in a capacitance touchscreen?
Considering that silver has a conductivity of 62 million siemens per metre, something that has a conductivity of 10 thousand siemens per cm (100 siemens per metre) isn't that great. Compare it with salt water at about 5 siemens per metre and it starts to look OK but inside a capacitive touch screen the conductors are very thin printed tracks with a print width of a few thousandths of an inch at best: -



The picture is stolen from here and as you can see, the cap screen needs an XY matrix of conductors separated by a thin layer. If you start to reduce the conductivity of these conductors you will get to a point where the XY matrix becomes ineffective and it doesn't work.

How much you can lower the conductivity is something that is difficult to say. If the overall resistance of the XY conductors starts to approach the capacitive reactance decrease due to your finger on the screen then reliable operation is going to be affected. However, it seems that even with a few pF extra when the finger is placed on the screen, to not detect this reliably would mean a conductivity that is hundreds of times lower than 100 siemens per metre.