A coating layer (12) is formed on a base film (10) by heat resistant resin having a Tg (glass transition temperature) of 120 DEG C or more, and more preferably 200 DEG C or more, and a functional thin film (14) is produced by printing ink composite including conductive particles on a surface of the coating layer (12) and thereby forming an ink layer. This functional thin film (14) is sintered by heating performed by photo irradiation, and a conductive layer is formed thereby.