High-Refractive-Index Photosensitive Siloxane Coatings for Optical Fingerprint Sensor

Abstract

Optical sensors composed of microlenses and thin-film transistor sensors are attracting increasing attention for use in next-generation fingerprint sensing technology that is intended to achieve large-area fingerprint recognition. Such optical sensors would allow smartphones to recognize multiple fingers and thus increase their security level. In this paper, we introduce novel high-refractive-index photosensitive siloxane coatings. These coatings have a high reflowability that allows them to form microlenses by controlling the glass transition temperature, which is determined by the specific combination of difunctional units and trifunctional units used in the siloxane polymer. The coatings also have excellent optical properties, high heat resistance, and high heat stability. These promising features mean that the photosensitive coatings presented here are suitable for fabrication of microlenses for next-generation fingerprint sensors.