NCR means No Carbon Required (also known as Carbonless) and refers to special paper which negates the need for the blue carbon paper once commonplace.
Instead copy is produced by the pressure of writing or printing as the result of a colour reaction.
To achieve this, two coatings applied to the front and back of the base paper react with each other.
The coating consists of microcapsules containing dissolved colourless colour formers. It is only the pressure of writing or printing that destroys the microcapsules.
At least two types of sheet are required to make form sets.
In the case of form sets with more than two sheets another type of sheet is needed for the middle.
Carbonless Papers are handled just like other coated or uncoated papers. They are just slightly more sensitive to pressure.
CB = coated back (top sheet)
CFB = coated front and back (intermediate or middle sheet)
CF = coated front (bottom sheet)
Source: Under the well-known giroform brand Mitsubishi HiTec Paper Europe produces high-grade carbonless paper with black copies on woodfree base paper.