Roll-to-Roll Gravure Printing Functional Films And Their Applications

Gravure printing of flexible electronic has attracted many attentions due to its advantages of large area,high throughput and low cost.However,due to the influence of various factors,some defects will be generated in the printing process,and the influencing factors are closely related to the printing process and the rheological characteristics of the ink.In order to investigate how various parameters affect the resolution of printing patterns,we first designeds different numbers of screening lines on the gravure rollers to carve different shapes of gravure cavities,and uses these different cavities to form line patterns of different widths,while determining the process of making rollers.Before the actual printing,ANSYS Fluent was used to simulate the transfer process of the water-based conductive carbon paste ink between the miniature screen cavities and the substrate,converting the actual printed screen cavities and the substrate into a two-dimensional model.The width and depth of the cavities were set as independent variables which were investigated separately for their influences,on ink release and pattern formation Based on the results,the experiments were conducted and the results were compared between the simulation and the experiment to determine the ink transfer rate by the area method.The effects of printing speed,ink viscosity and mesh cavity shape on the ink transfer rate were obtained.With 100 l/cm of screening lines at shallower mesh cavities,the increase of the printing speed from 0.6 m/min to 1.5 m/min,led the decrease of the viscosity the water-based conductive carbon paste,furthermore the decrease of ink transfer rate that resulted more residual ink in the mesh cavity.For the ink viscosity of 8000 m Pa·s to 14000 m Pa·s,the ink transfer rate would increase with the increase of the ink viscosity.In addition,the ink transfer rate varies between different cavities,as general,the increase in cavity depth would result in decrease of,the ink transfer rate,and the closer the fracture point to the cavity.Next,the rheological properties of water-based conductive carbon paste,PVP dielectric ink and water-based conductive silver paste were studied,and the effects of printing parameters and ink rheology on printing results were compared.The results showed that the line width increased proportionally slower as the viscosity increased in water-based conductive carbon paste,but the change rate was decreased moving toward the high viscosity.For the dielectric ink,of the 30% of PVP,the fidelity of printed line width was not high for the low viscosity ink.The film thickness increased by about 181%,when viscosity changed from 1200 m Pa·s to 3600 m Pa·s.Among the water-based conductive silver pastes,the sheet resistance was the smallest when the printing speed reached 2.7 m/min.Finally,after determining the printing parameters,the flexible capacitors were fully gravure printed using water-based conductive carbon paste and dielectric ink PVP printed layerby-layer to form the sandwich structure.The changes in capacitance and leakage loss of the flexible capacitors were compared under different printing parameters and ink rheology.At the right frequency,the dielectric loss before and after optimization were 0.08106 and 0.04658,respectively,and the optimized dielectric loss decreased by about 42.5%,and the optimized capacitance value was improved by 28.1%.For the Si O2 doped in the dielectric ink PVP and the cross-linked PMF were also used in the dielectric layer to prepare flexible capacitors with different dielectric inks,and the device performance was compared using LCR: the dielectric loss of the capacitors printed with the three dielectric materials was reduced from the highest0.071 to 0.044,and the change in capacitance value was within a reasonable range.In addition,RFID antenna and NFC antenna were printed using water-based conductive silver paste.The effect of line width on RFID antenna performance was simulated using ANSYS HFSS software.When the center loop width of the simulated and designed tag antennas is the same,the resonant frequency of the printed RFID tag antenna is 840 MHz and the return loss is-20.466 d B at the best printing speed of 2.7 m/min,which differs from the simulated resonant frequency result by11.6% and the return loss differs from the simulation by 11%.When the printed NFC antenna coupled with the cell phone NFC,the LED light in the NFC antenna loop could be lighten up.