Electrostatic capacity type touch sensor for detecting a large number of touch positions with a small number of detection electrodes

An electrostatic capacity type touch sensor, comprising:

• a substrate;
• a first common electric potential line disposed on the substrate;
• a second common electric potential line disposed on the substrate adjacent the first common electric potential line;
• first, second, third and fourth detection electrodes disposed on the substrate in a region interposed between the first common electric potential line and the second common electric potential line;
• a charge amplifier generating a first output voltage and a second output voltage, the first output voltage being proportional to a capacitance difference between a capacitance of a first capacitor formed between the first detection electrode and the first and second common electric potential lines and a capacitance of a second capacitor formed between the second detection electrode and the first and second common electric potential lines, the second output voltage being proportional to a capacitance difference between a capacitance of a third capacitor formed between the third detection electrode and the first and second common electric potential lines and a capacitance of a fourth capacitor formed between the fourth detection electrode and the first and second common electric potential lines;
• first to fourth terminals electrically connected to the first to fourth detection electrodes, respectively, for applying the charge amplifier with voltages corresponding respectively to the capacitance of the first capacitor, the capacitance of the second capacitor, the capacitance of the third capacitor, and the capacitance of the fourth capacitor, the first to fourth terminals being included a first wiring layer;
• and
• a common electric potential line electrically connecting the first common electric potential line and the second common electric potential line, the common electric potential line being included in a second wiring layer different from the first wiring layer, the common electric potential line electrically isolated from and overlapping the first detection electrode in a plan view of the electrostatic capacity type touch sensor,
• wherein the first common electric potential line is disposed on a circumference of a first arc with a first radius and the second common electric potential line is disposed on a circumference of a second arc with a second radius, the first and second arcs sharing a common center and the second radius being larger than the first radius, and wherein a boundary region between the first detection electrode and the third detection electrode is set so that an area of the first detection electrode included in a sector form of the second arc having a predetermined center angle decreases as the sector form rotates and an area of the third detection electrode included in the sector form increases as the sector form rotates.