UV stabilized multi-layer structures with detectable UV protective layers and a method of detection

A method of detecting an ultraviolet protective layer in an ultraviolet stabilized multi-layer structure comprising the steps of:

• (a) preparing an ultraviolet stabilized multi-layer structure having
• (1) an ultraviolet protective layer comprising an ultraviolet absorbing compound;
• a polymeric base material selected from the group consisting of a polyester, an acrylic and a polycarbonate;
• and an optical brightener present in an amount sufficient to cause visual illumination of the ultraviolet protective layer upon exposure to a white light source;
• and
• (2) a polymeric layer comprising a polyester or a polycarbonate;
• (b) applying a white light source to the ultraviolet stabilized multi-layer structure;
• and
• (c) visibly determining the location of the ultraviolet protective layer by its illumination;
• wherein the ultraviolet absorbing compound is a fluorescing material with the optical brightener being present in an amount between 1 and 1000 ppm or the ultraviolet absorbing compound is a non-fluorescing material with the optical brightener being present in an amount between 200 and 1000 ppm, the amount of optical brightener being based on the total weight of the polymeric base material in the ultraviolet protective layer.