What is the technology behind microcapsules in NCR paper and how are they made?

The technology behind microcapsules in NCR paper involves the encapsulation of reactants within tiny, spherical structures known as microcapsules. These microcapsules are designed to rupture when pressure is applied during writing or printing, releasing the encapsulated reactants and initiating a chemical reaction. The process is intricate and relies on precision in both microcapsule formation and the choice of reactant materials. Here is a detailed explanation of the technology:

Formation of Microcapsules:

Encapsulation Materials:

Microcapsules are typically formed from materials such as gelatin or other polymers. These materials are selected for their ability to form a protective shell around the reactants, allowing for controlled release during pressure application.

Reactant Selection:

The microcapsules contain reactants necessary for the chemical reaction to occur. The key components include a colorless dye and a color developer. The color developer is often an acidic substance that reacts with the dye to produce a visible color.

Emulsion Process:

The encapsulation process begins with the creation of an emulsion, a mixture of oil-based and water-based components. The reactants are dissolved or dispersed in the oil phase of the emulsion.

Droplet Formation:

The emulsion is then subjected to a process that forms droplets of the oil phase containing the reactants. This can be achieved through methods such as stirring or spraying.

Polymerization or Crosslinking:

The droplets are solidified into microcapsules through polymerization or crosslinking of the encapsulation materials. This creates a thin shell around each droplet, isolating the reactants within.

Washing and Drying:

The microcapsules are then thoroughly washed to remove any excess materials and unreacted components. Subsequently, they are dried to stabilize the structure and prevent premature rupturing.

Sizing and Sorting:

Microcapsules are often sorted based on size to achieve uniformity. This step is crucial for consistent pressure sensitivity during writing or printing.

Pressure-Induced Rupture and Chemical Reaction:

Application of Pressure:

When pressure is applied to the NCR paper, such as during writing or printing, the microcapsules rupture. This pressure-induced rupture is essential for releasing the encapsulated reactants.

Release of Reactants:

Upon rupture, the colorless dye and color developer are released into the surrounding area. The specific reactants used determine the color that will be developed during the chemical reaction.

Chemical Reaction:

The colorless dye reacts with the color developer in the presence of pressure, forming a visible color. This chemical reaction occurs on the adjacent sheets of the NCR paper, producing duplicate or triplicate copies without the need for carbon paper.

The technology behind microcapsules in NCR paper is finely tuned to ensure controlled and consistent release of reactants, enabling a reliable and efficient carbonless copying process. This technology has been refined over the years to optimize copy quality, stability, and the overall performance of NCR paper in various applications.