The photodegradation of inkjet prints is a multi-layer process. It includes several factors, such as ink as a complex mixture of colorants and various accompanying substances, paper, which in addition to various fibres also contains other components (e.g. optical bleaching agents), and external factors (e.g. temperature, humidity, and the strength and spectral composition of the radiation from a light source). The aim of the doctoral dissertation was a systematic analysis of the complex process of degradation of prints made with an inkjet printer. Selected types of paper and printers with dye-based inks were included in the research. In the initial phase, the analysis of basic chemical and optical paper properties was performed. The TLC, GC/MS, FTIR methods enabled a systematic analysis of the printing ink and identification of components involved in the process of degradation in the solution and on the print. The influence of medium-wave UV radiation on the stability of printing ink solutions in an inert atmosphere and an atmosphere of oxygen was analysed. Moreover, the influence of light, medium-wave and short-wave UV radiation on inkjet prints, and individual components were studied. To monitor the dynamics of the degradation of paper, ink and prints, colorimetric parameters were used. The results showed that the changes in paper properties were mainly caused by short-wave UV radiation. The analysis of ink revealed that they contained 2–4 colourants and a considerable number of accompanying substances. The photodegradation of ink in an aqueous solution occurred most rapidly in the presence of light with higher short-wave UV radiation. Furthermore, the presence of oxygen increased the rate of ink degradation in the solution. In most cases, the degradation of prints was faster under the influence of light with higher short-wave UV radiation. As it turned out, the influence of the spectral composition of light depends on the type of ink as well as on paper, especially on the presence of optical brightening agents in it. Consequently, the prints on paper containing optical brightening agents had inferior fastness. The analytic methods used in this study enabled a thorough analysis of the degradation of individual components of prints. However, for the interpretation of the results, it was necessary to take into account that the degradation of prints represents an interaction of many internal as well as external factors. Therefore, the use of colourimetry proved to be an effective method to monitor the photodegradation process and accurately describe it with regard to the changes in the optical properties of prints. The results enabled a comparison of the rate of degradation of individual systems under different conditions, leading to the description of changes on prints, paper and ink.
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