Photochemistry is the science of how light interacts with matter – and most imaging is the result of this interaction. Not surprisingly, photochemistry is very important to Kodak, in both obvious and subtle ways. Many factors must be considered in order to tune the course of an excited molecule to suit a specific application.

The main areas of imaging technology that directly or indirectly utilize photochemistry include:

• Dyes
• Sensitizers
• Photoinitiators
• Photostabilizers
• Optical brighteners
• Filters
• Fluorophores
• Photochromics
• Photopolymers

In general, imaging is more than just color formation as a result of light exposure. It also includes:

• Color bleaching
• Changes in refractive index
• Changes in polarity or wettability
• Formation of a fluorescent material
• Ablation
• Deformation
• ...and much more

In addition, Kodak's constant desire for more environmentally sound imaging schemes, those that have simple or no processing, guides our search for novel solutions.

For instance, sensitization is a key process in most imaging schemes. In silver halide photography, spectral sensitization is a photochemical process involving photo-induced electron transfer. This very old discipline, but Kodak is investigating promising new concepts that enhance sensitivity. Sensitization also is an essential part of photopolymerization, which is widely used in photoresist and protective layer applications.

There more to photochemistry than image formation. This discipline is critical in determining image quality – especially the photostability of images. Designing high photostability dyes requires understanding the various electronic states of excited electrons (lowest-singlet and upper-excited states, as well as triplet states), as well as the lifetimes associated with each.

In electrophotography, charge carrier generation also employs many photochemical principles. And the same is true for the reverse process, charge recombination – which produces electronically excited molecules such those used in light emitting diodes (LEDs).