Previous research conducted by the Laboratory Hubert Curien developed photosensitive Ag: TiO2 films on glass as support for updatable or permanent patterns. An adaptation of this work to plastic and paper substrates is here proposed to expand the potential application areas at product secure labeling for example. Fabrication techniques of such Ag: TiO2 films compatible with studied substrates have therefore been developed. Two paths have been considered.
The first uses the combination of Sol-Gel chemistry with the EISA method. Deposition processes such as spin coating, inkjet or flexographic printing are used to form a mesoporous film of TiO2 on substrates. Treatments based on solvent extraction or infrared annealing have been devised to release the porosity of the film without damaging the supports. To make films on paper, a silver salt is added to the sol before its coating. In the case of films deposited on plastic, silver is incorporated by soaking the material in a silver salt solution.
The second developed option proposes formulating an aqueous ink jet ink of TiO2 nanoparticles and silver ions by adapting the composition of a commercial suspension of TiO2 with the requirements of the ink jet process. After printing, the ink is dried by infrared annealing. The photochromic behavior under UV and visible light exposures of fabricated films allows them coloring and bleaching reversibly. Sol-Gel films coated on plastic can also be a support for permanent colored patterns realized by irradiation with a visible light of certain intensity.