| Inkjet printing technology has been one of the most attractive printing methods,because of its advantages of no need of printing plate,no damage to substrate and high precision.However,the insufficient of the conductive ink,such as high cost and poor stability,limits the development of inkjet printing.Graphene has attracted extensive attention in the field of the preparation of inks due to its unique mechanical property and photoelectric performance.In this paper,high concentration graphene dispersions for inkjet printing were prepared by optimizing liquid phase exfoliation method.Firstly,the conductive ink with good droplet ejection pattern was obtained by adjusting the Z value.Then,the patterning process of inkjet printing was optimized by controlling the printing parameters,and applied into the preparation of transparent conductive films.The main work includes:Firstly,the liquid phase exfoliation method,which matched the inkjet printing printability requirements of ink viscosity and surface tension,was selected to prepare graphene.The influence factors on the concentration and structure of graphene were analyzed.In the experiment,the graphene dispersion was prepared by changing the peel test conditions,such as exfoliation solvent,graphite powder wetting,stripping power and time.The results showed that,when the concentration of the graphite powder mixed solution with the N-methyl pyrrolidone as solvent was 8 mg/ml,after been treated at 160 ? for 5h and peeled off at 40W for 16 h,the graphene dispersions with a concentration of 0.3mg/ml were obtained.The sample could be directly applied to the preparation of inkjet inks without additional purification processes.Secondly,in the preparation process of conductive ink,the range of Z values determines the formation of stable and continuous ink droplets.Since the Z value of the obtained graphene dispersion is not in the optimum range.In order to obtain better ink jet morphology,the Z value is adjusted by adding ethylene glycol.The Z value can be calculated by testing the density,surface tension and viscosity.The Fujifilm DMP 2800 printer was used to observe the morphology of ink droplets in the case of different Z values.The results showed that the ink with 20%ethylene glycol possessed good ink droplet ejection.Furthermore,the concentration of the ink was 0.27mg/ml with good dispersion and stability,which could be applied to patterning of inkjet printing directly.Finally,the limitations in the process of inkjet printing are explored,which included uneven ink film on flexible substrate,less research on the conditions of overprint and other defects.The influence of the experimental conditions on the thickness and uniformity of the printing ink film was analyzed.The main influence conditions are the settings of Epson ME-10 printer resolution,the relationship of surface tension between substrate and conductive ink,as well as the time,manner and number of overprint.The results showed that the ink on the PET substrate possessed better wettability.At the condition of highest resolution,the more evenly graphene film on PET substrate was obtained,which was repeated 12 times with "dislocation cross" overprint mode.The results showed that the increase of the number of overprint could improve the conductivity of graphene film.The transparency of the graphene film on PET substrate was better than that of ITO.Moreover,the graphene film on ITO substrate could enhance the mechanical electrical properties of ITO. |
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