NCR stands for No Carbon Required and is also sometimes refered to as CCP Carbonless Copy Paper. NCR paper is commonly used in receipt books or invoice books were the user needs instant copies of what is being written.
NCR paper was designed to replace the old carbon paper that was used to make copies by placing a sheet of carbon paper in between two sheets of paper. Transferring the carbon onto the bottom sheet when an impression was made on the top sheet by writing or another form of impact.
NCR paper works by coating the back of the first sheet with a micro-encapsulated dye. The front of the second sheet is coated with a clay that reacts with the dye on the back of the top sheet to form a permanent mark. Any middle sheets to make more than one copy would be double coated with clay on the front and dye on the back.
In printing we sometimes refer to the top sheet as carbon back (CB), the bottom sheet as carbon front (CF), and the middle sheets as carbon front and back (CFB).
NCR paper can be printed on in any way you want. From a single colour to four colour process.
When printing and assembling the books or pads that the NCR paper is being used in, it is obviously vitally important that the sheets are placed in the correct order. Otherwise the pads simply wont work.