In addition, in view of firmly and stably bonding the convex directionality-providing elements 12 to the base film 11, it is preferable to finish a surface of the base film 11 to which the convex directionality-providing elements 12 are to be bonded, by an adhesion improving process such as a corona discharge process. [0043]FIGS. 2A, 2B and 2C are a plan view and sectional views of the directional