Retroreflective prismatic retro-reflectors without visually disturbing seams

A process for producing a prismatic reflective material in which no join lines or seam lines are apparent, comprising the steps of:

• providing at least one mold having prismatic elements therein for making a prismatic retro-reflector with the at least one mold in a thermoplastic substrate;
• abutting edges of the at least one mold to form a mold structure wherein the abutting edges of the mold form a seam line;
• forming a retro-reflective thermoplastic sheet with the at least one mold wherein the retro-reflective sheet has a seam line corresponding to the seam line formed by the edges of the at least one mold;
• and
• forming a grid pattern on or in the retro-reflective thermoplastic sheet by a method selected from the group consisting of scribing the grid pattern into the retro-reflective thermoplastic sheet with a tool, stamping the grid pattern into the retro-reflective thermoplastic sheet, using a laser to etch the grid pattern into the retro-reflective thermoplastic sheet, printing the grid pattern into the retro-reflective thermoplastic sheet, or by combinations of these, which grid pattern is positioned such that the seam line in the retro-reflective thermoplastic sheet becomes a part of the grid pattern to be effectively obscured thereby.