Electrostatic sensing device

An electrostatic sensing device configured to measure electrostatic charge of a measurement target placed in front of the electrostatic sensing device, the electrostatic sensing device comprising:

• a plurality of sensor oxide semiconductor TFTs arrayed on a substrate;
• a plurality of switch oxide semiconductor TFTs on the substrate, the plurality of switch oxide semiconductor TFT each configured to select one of the plurality of sensor oxide semiconductor TFTs;
• and
• a controller configured to control the plurality of sensor oxide semiconductor TFTs and the plurality of switch oxide semiconductor TFTs,
• wherein each of the plurality of sensor oxide semiconductor TFTs includes:
• a first oxide semiconductor active layer;
• a first source electrode connected with the first oxide semiconductor active layer;
• a first drain electrode connected with the first oxide semiconductor active layer;
• a first gate electrode behind the first oxide semiconductor active layer;
• and
• a first gate insulating layer between the first gate electrode and the first oxide semiconductor active layer,
• wherein each of the plurality of switch oxide semiconductor TFTs includes:
• a second oxide semiconductor active layer;
• a second source electrode connected with the second oxide semiconductor active layer;
• a second drain electrode connected with the second oxide semiconductor active layer;
• a third electrode in front of the second oxide semiconductor active layer;
• and
• a second insulating layer between the third electrode and the second oxide semiconductor active layer, and
• wherein the controller is configured to:
• apply a predetermined voltage to the third electrodes in measuring the electrostatic charge of the measurement target;
• control the plurality of switch oxide semiconductor TFTs to select the plurality of sensor oxide semiconductor TFTs one by one;
• measure a difference from a reference current of a current flowing between the first source electrode and the first drain electrode, while applying a driving voltage to the first gate electrode of a sensor oxide semiconductor TFT selected from the plurality of sensor oxide semiconductor TFT;
• and
• determine intensity of an electrostatic field generated by electrostatic charge of the measurement target based on direction and amount of the difference.