At substantially the center position of the fold-up section 9 a cut 18 is formed along an imaginary fold-up line, the ends of which do not reach the margins of the base film 13 and the conductive layer 17 traversing the foregoing turn-up line, and at either end of the cut 18 there is formed a thru-hole 19 of any shape such as circular, elliptical, triangular, or quadrangular, to prevent generation