Thermoset relief patterned sheet

A flexible, composite sheet material having a patterned relief surface of high quality and definition, said composite sheet material comprising a flexible optically transparent base film of a thermoplastic polymer, said base film being of predetermined, substantially uniform width and of indeterminate length, and said base film having opposing front and rear surfaces with the distance therebetween varying over the length and width of the base film due to inherent accuracy limitations in the production of said base film and resulting in relatively small but measurable variations in the thickness of the base film, and an optically transparent coating of an actinic radiation cured thermosetting polymer extending over substantially the entire front surface of said base film and bonded thereto, said coating having a nonplanar outer surface defined by a plurality of relief formations forming a predetermined relief pattern of high quality and durability and of fine definition in said thermosetting polymer layer, said relief formations being of uniform size throughout the composite sheet material, and the thickness of said cured thermosetting polymer layer in which the relief formations are formed compensatingly varying in relation to said variations in thickness of said base film so that the distance from the outermost surface portions of the relief formations to the rear surface of said base film is uniform throughout the composite sheet material in spite of said variations in thickness of the base film whereby variations in thickness in the overall composite sheet are eliminated.