Moir？-free fingerprint sensors based on multilayer oxide-metal-oxide electrodes

Abstract: Touch screen device based on on-screen type fingerprint sensor may deteriorate the display quality by the moir？ pattern visually recognized by overlapping between a display pattern and fingerprint sensor pattern provided on a display. One promising strategy for this issue is to prevent the visibility of the moir？ pattern by providing the filling layer having the light transmittance similar to the electrode between the electrode patterns. Herein, moir？-free fingerprint sensor is proposed using oxide-metal-oxide (IZO/Ag/IZO) multilayer as a highly transparent electrode. To prove the moir？ reduction effect, two-dimensional (2D) spectral analysis was performed to calculate the spatial frequencies of the superimposed image of the display and the sensor pattern and visibility circle were used to roughly quantify the degree of visibility of the pattern. By minimizing the difference of the refractive indexes of the non-conductive region and the conductive region, the sensor recognizes that there is no optical pattern. It is found that the moir？ visibility problem formed by overlapping with the display pattern can be fundamentally solved. Additionally, since the proposed electrode has low resistance of less than 7 ohm sq^-1, it is considered as a promising candidate technology for on-screen fingerprint sensor.