Meaning
Molecular interactions occur when light energy is taken up by the atoms in a material and converted into other forms of energy. In the context of printing and packaging, photon absorption is the primary driver of the chemical changes that lead to fading and degradation. The amount of energy absorbed depends on the wavelength of the light and the electronic structure of the pigment molecules.
This process can trigger a chain reaction that breaks down the molecular bonds of the colorant or the substrate.
Energy Interaction
Molecules reach an excited state when they capture the energy from a specific photon. The likelihood of photon absorption is higher for ultraviolet light because it carries more energy per particle than visible light. Once a molecule is excited, it must release that energy through heat, light emission or a chemical reaction.
If the energy is not dissipated safely, it can lead to the permanent destruction of the color.
Molecular Reaction
Photochemical pathways are created when the absorbed energy is used to rearrange the atoms within a pigment. During the process of photon absorption, the color of the sample changes as the old molecular structures are replaced by new ones that do not reflect light in the same way. The rate of this reaction is influenced by the presence of oxygen and moisture in the environment.
Antioxidants and uv absorbers are often added to the material to intercept the energy before it can cause damage. Every pigment has a specific threshold of energy that it can handle before it fails. Understanding these thresholds allows manufacturers to select the right materials for high light environments.
Stability Threshold
Limits on the total energy dose help in predicting the shelf life of a product in a retail setting. High levels of photon absorption indicate that the material will fade quickly if not protected.
