Capacitive touch screen

Projected Capacitive Touch Panel (PCAP) was actually invented 10 years earlier than the first resistive touchscreen.   But it was no popular until Apple first used it in iPhone in 2007. After that, PCAP dominates the touch market, such as mobile phones, IT, automotive, home appliances, industrial, IoT, military, aviation, ATMs, kiosks, Android cell phones etc.

Projected capacitive touchscreen contains X and Y electrodes with insulation layer between them.   The transparent electrodes are normally made into diamond pattern with ITO and with metal bridge.

Fig. 1. P-CAP X and Y electrode structure

Fig. 2. Metal Bridge in P-CAP

Human body is conductive because it contains water. Projected capacitive technology makes use of conductivity of human body. When a bare finger touches the sensor with the pattern of X and Y electrodes, a capacitance coupling happens between the human finger and the electrodes which makes change of the electrostatic capacitance between the X and Y electrodes.   The touchscreen controller detects the electrostatic field change and the location.

Capacitive Touchscreen Advantages

In There are many advantages for P-CAP:

· Projected capacitive supports multiple touches (Multi-touch), so it supports a lot of gestures: Zoom in and out (pinch/spread), scroll, swipe, drag, slide, hold/press, rotate, tap etc.

· Excellent image clarity because of high transmission.

· Excellent sensitivity.

· More resistance to the scratches because the surface can be made by tampered glass, such as gorilla glass or dragontrail glass which can have the surface hardness of 9H. Only diamond can make a scratch.

· Resistance to contaminants and liquid. It is easier to get clean of dust, grease, moisture etc.

· With the new development, projected capacitive touch panels can support gloved hand touch with different glove materials and touch with water or even with salt water.