Dye Diffusion Digital Imaging

During the dye diffusion thermal printing process a dye-carrying ribbon is brought into contact with a receiver and these two surfaces are compressed between a printhead bead and elastomeric drum, creating the thermal printer nip. Within this highly pressurized contact region both heat and mass transfer takes place. In order to better understand the printing process we have created a finite difference model that simultaneously solves the heat and dye diffusion equation. Using experimental head temperature data we will describe a method for determining a surface boundary condition that can be used in the simulation. This boundary condition will allow us to incorporate different pulse modulation heating schemes in order to predict temperature variations and dye penetration patterns. In the discretization of the diffusion equation we will account for concentration dependence of the diffusivities that is common in many polymer systems. This consideration leads to a nonlinear governing equation for the dye diffusion process.