The digital transfer printing process is divided into two steps: i) the digital print of an image on the transfer paper and ii) the thermal transfer (sublimation process) of the printed image onto the textile or other polymer substrates.Based on the sublimation model the thermal transfer process is explained and the critical physical parameters are evaluated: affinity of the dye to the paper and sublimation enthalpy of the dye.Analyzing the spectral behavior of transfer dyes transferred at different temperatures the activation energy for the transfer printing process is evaluated and compared to the sublimation enthalpy of the dye.The spectral behavior of transfer papers before and after transfer show a dramatic change in shade. This clearly indicates a fixation of the transfer dye on / in the paper surface. As a conclusion to evaluate the whole transfer printing process it is necessary to take the distribution equilibrium between the paper and the substrate into account: The higher the affinity of the paper to the dye, the lower is the color strength on the substrate.Based on the physical properties of transfer disperse dyes the consequences on color generation and reproducibility are discussed.