WEB THICKNESS MEASURING DEVICE AND WEB MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a thickness measuring device in which accuracy in the measurement of web thickness is improved and a web manufacturing method in which variations in the thickness of a web is substantially reduced. SOLUTION: A measuring part 7 of a light-interference thickness gauge is made to scan the traveling web W in the widthwise direction of the web to detect wavelengths which indicate a maximum value and a minimum value in a wavelength intensity distribution by the interference between two types of reflected lights I and II at the surface and back surface of the web. The thickness of the web is computed from the wavelengths and the refractive index of the web in the device. The refractive index distribution of the widthwise direction of the web is stored in an operation part 8 of the light- interference thickness gauge, a refractive index corresponding to the scanning location of the measuring part 7 in the widthwise direction of the web is specified from the refractive index distribution, and the thickness of the web is computed through the use of the refractive index.