Ciba has been investigating novel photo-induced effects (triggered by UV-Vis light) that do not necessarily involve initiators for curing. For example, a range of novel additives that are colorless (pre-chromic) and thermally stable is currently under development.

When irradiated with the appropriate wavelength, the color develops instantaneously. Irradiation can be carried out with full exposure or through a photomask, providing either a full colored article or an image in the carrier material.

The method is especially suitable for instantaneous in-depth coloring of a coating composition, which has the advantage that the image obtained cannot be removed without disturbing the coating.

Pre-chromics can be incorporated and cured in conventional baking systems without any color formation since the latent, colorless system is stable under thermal curing conditions. On exposure to UV radiation a wide range of colors can be obtained instantaneously. The photo process can be triggered using standard UV irradiation conditions, such as a medium-pressure mercury bulbs.

In addition UV lasers can be employed to generate writing or images without the need for a photomask, which makes the system suitable for brand protection of coated substrates. The slow color formation under long-wave UV exposure can be exploited as a sensitive dosimeter for UV exposure.

Due to the immediate and intense color formation under conventional UV curing conditions, photolatent colorants are also useful as processing aids (UV indicator) in UV curable formulations to visualize the degree of UV exposure and through cure in UV curing processes in coatings, adhesives and for the formation of three-dimensional objects.