Visualization of contact patterns of thermal printhead for indirect thermal transfer printing

摘要

Printers often face problems with large power consumption, resulting in the development of various power saving techniques. Such techniques for indirect thermal transfer printers covered in this study are also progressing. For this type of printer, most of the required electric power is consumed during the ink transfer process, in which ink on a transfer belt is heated using a heating roller with large heat capacity. To reduce the heat capacity of the heating system, the use of a thermal printhead with a low thermal capacity has been proposed. Even at low power, such a thermal printhead will immediately reach high temperatures within a specified area, shortening the warm-up time and leading to lower printer power consumption. However, thermal printheads have two problems with contact heat transfer. The first is that the thermal printhead is less likely to deform than the soft heating roller. Secondly, since the wiring for power supply is complicated, irregularities of several μm are formed on the surface of the printhead, resulting in the limited heat transfer. To evaluate these effects, distribution of contact pressure with respect to surface waviness was analyzed using the finite element method. In this study, we observed the real contact area using a wide-field laser microscope and evaluated the validity of the FEM analysis. We succeeded in visualizing the contact pattern by pressing the ultra-high transparent silicone rubber and the transparent plastic film against the thermal printhead. As a result, it was confirmed that the FEM simulation results agree with the experimental ones.