Carbonless copy paper (CCP), non-carbon copy paper, or NCR paper (No Carbon Required)
Carbonless copy paper consists of sheets of paper that are coated with micro-encapsulated dye or ink or a reactive clay. The back of the first sheet is coated with micro-encapsulated dye (referred to as a Coated Back or CB sheet). The lowermost sheet is coated on the top surface with a clay that quickly reacts with the dye to form a permanent mark (Coated Front, CF). Any intermediate sheets are coated with clay on top and dye on the bottom (Coated Front and Back, CFB).
When the sheets are written on with pressure (e.g., ball-point pen) or impact (e.g., typewriter, dot-matrix printer), the pressure causes the micro-capsules to break and spill their dye. Since the capsules are so small, the print obtained is very accurate.
Carbonless copy paper was also available in a self-contained version that had both the ink and the clay on the same side of the paper.