Touch screen technology put under display

Peratech has created a touch screen solution for OLED displays, monitors and large interactive displays that can be placed behind the OLED screen and still detect finger touches on the front of it.

By creating a touch screen interface in this way using its QTC Ultra Sensor, Peratech says there is no loss of light from the display, allowing it to be more energy efficient.

"The slight light loss from having this layer is on a par with existing Resistive and Capacitive touchscreen technologies but, by putting the sensor behind the display, there is no light loss at all," said David Lussey from Peratech. 
"Currently, sensors go over the display and absorb light which has to be compensated for with a brighter setting for the display and that uses up more battery life. It works best with OLED and e-paper type displays, which are becoming increasingly popular, although it can be used with other display technologies providing they can be pressed so LCDs are not advisable.”

Peratech uses Quantum Tunnelling Composite material which is anisotropic and changes its resistance when pressure is applied and only at the point where pressure is applied.

Power is only used when touched unlike Capacitive, which needs to continually power the active sensing matrix. Capacitive technology also becomes increasingly expensive as the display size increases due to the design challenges of the matrix creating interference, but QTC Ultra Touch Screens can be made using standard ink printing techniques to any size and Peratech has already made examples that are 2m by 1m.

The layer of QTC material is printed as a QTC ink on the back of the display as required by the product designer. QTC material has nano-sized particles of conductive material evenly distributed in a non-conductive polymer. When a force is applied the particles move close enough for electrons to flow between the particles using an effect called Quantum Tunnelling.