PURPOSE: To monitor the thickness or action of a coating layer at a time of production, in a plastic plate or sheet equipped with a core layer sensitive to UV rays and a plastic coating layer containing a component absorbing irradiated UV rays, by adding a fluorescent dye to the nuclear layer.
CONSTITUTION: An UV-protected plastic plate or sheet is equipped with a core layer sensitive to UV rays. At least one relatively thin coating layer made of plastic containing a component absorbing irradiated UV rays provided on one surface of the core layer. Further, one of both layers contain a fluorescent dye capable of being activated by UV rays. In this case, the fluorescent dye is added to the core layer. By this constitution, during the production of the plastic plate or sheet by the coextrusion of the core layer and the coating layer, the thickness or action of the coating layer can be monitored.
HORUSUTO GUREEPU
MIHIYAERU MAIAA-KAIZAA
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