Patent ID: 8531680

Claim:
A method for detecting a width of a coated film that is formed on an elongated sheet-like substrate along the longitudinal direction of the substrate, the width being detected in a transverse direction intersecting this longitudinal direction, the method comprising the steps of: (a) measuring a thickness profile in the transverse direction of the coated film at a predetermined measurement point in the longitudinal direction, the thickness profile being defined as a thickness Y of the coating film from a reference point Y 0 relating to the thickness, with respect to a distance X in the transverse direction from a reference point X 0 relating to the width; (b) creating approximating curves of a function of the distance X and the thickness Y in end-proximal regions of both ends of the coated film in the transverse direction, on the basis of the measured thickness profile; and (c) taking, as the both ends in the transverse direction, a distance X e1 corresponding to a thickness threshold Y t determined from the approximating curve of one end-proximal region and a distance X e2 corresponding to said thickness threshold Y t determined from the approximating curve of the other end-proximal region on the basis of the approximating curves obtained for the end-proximal regions of the both ends in the transverse direction and said thickness threshold Y t from the reference point Y 0 that has been set in advance, and calculating an absolute value of a difference between X e1 and X e2 , that is, X e1 −X e2 , as a width of the coated film in the transverse direction at the predetermined measurement point.