. . "If a layer of a transparent plastic, on which is deposited various amounts of such a compound, such as Cyasorb UV24???, or Cyasorb UV9???, etc, (American Cyanamid, Bridgewater, New Jersey) is laminated over a layer of the films of the invention, the color change response to ultraviolet light will be altered in proportion to the amount of Cyasorb??? which effectively masks\" any given area." . .