Research On The Film Formation Mechanism Of Electrospray Deposition Thin-Film Encapsulation

Electrohydrodynamic(EHD)printing technology has the advantages of high resolution and wide adaptability to solutions,which is an innovative way to the novel display manufacturing processes.As a kind of electrohydrodynamic printing technology which can produce encapsulation film in large area with high efficiency and high quality,electrospray deposition(ESD)technology has great development potential.At this stage,the research on the electrospray deposition film formation process is still insufficient,and the mechanism of influencing factors at each stage of film deposition is still unclear.To this end,we systematically explored the process of depositing micro-nano liquid film by electrospray technology in this paper,constructed a numerical simulation model of electrospray deposition film formation,summarized the action of various influencing factors in the process of droplet coalescence and the influence of process control parameters on the quality by electrospray deposition film formation,improved the parameter setting method on film forming process,and achieved the electrospray thin film deposition with less than 5% film thickness non-uniformity.It provides a theoretical basis and feasible ideas for the process parameters improvement by electrospray deposition technology.The main research contents of this paper are as follows:(1)Based on the phase field method,constructed a numerical simulation model of droplet electro-coalescence.Firstly,the overall process of the electrospray deposition film formation was systematically analyzed.Then,based on the research status,that it is difficult to directly observe the electrospray deposition film formation process,gave a numerical analysis solution.Finally,by analyzing the force of the droplet electro-coalescence on the substrate and combining with numerical analysis methods,constructed a droplet electrocoalescence numerical simulation theoretical model based on electric field force control equation,two-phase flow motion control equation,interface change tracking equation and surface tension control equation.(2)Based on numerical simulation,the mechanism of droplet electro-coalescence in the process of electrospray deposition film formation was studied.Firstly,completed the construction for the gas-liquid two-phase flow simulation model of double droplets electrocoalescence and the gas-liquid two-phase flow simulation model of multi-droplet film formation under a non-uniform electric field based on the droplet electric coalescence theoretical model.Then,explored the process parameter range of the double droplets electro-coalescence on the substrate,the allowing process parameters phase diagram of double droplets electro-coalescence was drawn.Finally,analyzed the influence of each process parameter on the double droplets electro-coalescence process and the multi-droplet film formation process under non-uniform electric field,and summarized the law of each influencing factor from multiple angles.The results indicate that the action mechanism of various factors in double droplets electro-coalescence process is consistent with the mechanism of various factors in multi-droplet small-scale film formation process.(3)Designed the experimental scheme of electrospray deposition film formation,verified the accuracy of the numerical simulation conclusions,summarized the effect of various process parameters on the electrospray deposition film formation quality,and realized the preparation of high-quality electrospray deposition thin film.Firstly,completed the design of the experimental scheme for electrospray deposition film formation by establishing an experimental platform for electrospray film formation,determining the main research parameters of electrospray deposition technology with thin film quality detection parameters,and introducing the experimental solution configuration method with the preparation steps of electrospray deposition film forming process.Then,clarified the criterion of stable continuous electrospray in the experiment.Summarized the influence law of each process control parameter in the process of electrospray film formation.This influence rule is consistent with the conclusion of numerical simulation,which verified the accuracy of numerical simulation.Finally,based on this influence rule,the process parameter setting method is improved,and realized the electrospray preparation of the deposited film with the film thickness unevenness less than 5% and the average film thickness less than 20μm.It provides a theoretical basis and feasible improvement ideas for the process parameters improvement of electrospray deposition thin film production.