フィルムロール内空気層厚さの非破壊定量検出法の開発

抄録

In the final stage of film production, films are typically wound to form a roll, and it is known that air is entrained into the roll during the film-winding. Since the amount of air is one of the factors causing winding defects such as slippage and wrinkling, it has been desired to detect to the air layer thickness non-destructively and quantitatively. In our previous study, we proposed a non-destructive inspection of film rolls by using optical coherence tomography (OCT), which is a three-dimensional imaging technique based on low coherent light interference, and demonstrated that OCT can visualize in-roll structures of film rolls and detect air gap sizes in the film roll quantitatively. However, the air layer thickness cannot be detected if the thickness is smaller than the spatial resolution of OCT. In the present study, we propose a method to detect the air layer thickness smaller than the spatial resolution of OCT. To validate the method, we made film roll samples with air layers smaller than the spatial resolution of OCT by manually winding a film and applied the method to the samples. The experimental results showed that the proposed method can quantitatively detect the air layer thickness in film rolls with sub-microscale and showed a significant difference between air layer thicknesses of film rolls made by soft and hard windings. Although further validation under controlling the film-winding condition is needed, the proposed method will be a promising inspection to prevent the occurrence of winding defects.