Optische Schichtdickenmessung von funktionellen Nassbeschichtungen auf Kunststofffolien

Continuous functional wet coating provides polymer films with additional functional properties. The industrial application requires powerful quality control, which can be achieved by in-line characterization of the coating thickness with optical spectroscopy directly on the coating equipment. To implement this concept, at first, model films were used to determine the optical parameters of the coatings. We have shown that thickness measurement is possible by using the intensities of molecular oscillation in the infrared spectral region as well as by thickness interferences in the visible and near infrared spectral region. For integration into the industrial coating unit, interferences in the near infrared region were selected and measured on functional polymer-like coatings on polyethylene terephthalate (PET) films. It was shown that in-line thickness measurement can be performed under usual operational conditions of the wet coating unit. Variations in the process parame ters were detected and the feasibility for a continuous quality assessment of functional wet coatings was demonstrated.