Printing paper has been used for decades. The traditional blue carbon ink compound paper is almost out of date. It is popular with carbon free paper. It does not need to add carbon paper between paper and paper. It can be directly duplicated, direct color display, small pollution, easy to use and so on. It is used more and more widely. Carbon free paper is also known as pressure sensitive recording paper. Invented by NCR (National Cash Register) in 1954, after decades of continuous development and improvement, industrial production has reached a certain scale.

Carbonless copy paper can be divided into two types: color rendering and self developing. The process of color rendering is to spilt the force sensitive pigment and oil solution in the microcapsule under the effect of external force, and the reaction occurs after contact with the color reagent, thus achieving the rewriting effect.

For the composition of carbon free carbon paper, there are at least two different coatings, namely microcapsule coating and chromogenic coating.