Study On Preparation Of Ulrtafine Silver Nanowires And Coating Process Of Transparent Conductive Films

With the development of flexible display devices towards lightweight and wearable,silver nanowires-based transparent conductive films（AgNWs-TCFs）as replacements for indium tin oxide transparent conductive film（ITO-TCFs）has become a research hotspot because of its high conductivity,high transmittance,strong flexibility and low cost.However,the research on the preparation method of high-aspect-ratio and ultra-fine AgNWs is still immature.In addition,the preparation method of large-size AgNWs-TCFs has not been studied in detail,and it is still unable to meet the needs of large-scale industrial production.The application of AgNWs-TCFs is significantly limited.Aiming at the immature preparation technology of high-aspect-ratio and ultra-fine AgNWs,this paper used polyols to prepare ultra-fine AgNWs.The effects of reagent purity,sodium bromide dosage,solvent and external reducing agent on the diameter and aspect-ratio of AgNWs are studied.With the increase of purity of AgNO₃ and NaCl,the diameter of AgNWs becomes smaller and the silver particles decrease gradually.With the increase of NaBr,the diameter of AgNWs decreases first and then increases.When Cl^-:Br^-=2 is added,the diameter of AgNWs is the smallest,about 20 nm.When ethylene glycol is used as solvent,the diameter of AgNWs is the smallest.Adding reductant outside can adjust the reduction kinetics and control the growth of AgNWs.With the increase of reducing dosage of polyester,the amount of AgNWs first increases and then decreases.When the amount of AgNWs is 1.5 g,the silver particles in AgNWs slurry are the least.Based on the optimal conditions,ultra-fine AgNWs with a diameter of about 20 nm,a length of about 40μm and aspect-ratio of about 2000 are prepared.In view of poor comprehensive performance and immature coating process of large size AgNWs-TCFs,the scraper coating method is used to explore the best coating process for large-area,high permeability and high conductivity AgNWs-TCFs.This paper mainly breaks through the problem of uneven coating caused in large-area coating process from two aspects of AgNWs slurry and coating process parameters.For the study of AgNWs slurry,the main research is to add thickener to the slurry to improve its stability and homogeneity,thus affecting the conductivity of the film.Adding a small amount of carboxymethyl cellulose（CMC）is significantly improved the dispersion and stability of the slurry.With the increase of CMC content,the permeability of the film decreases gradually,and the square resistance decreases.When the mass fraction of CMC is 0.75%,the film has the best photoelectric performance.At the same time,the parameters of coating process equipment are studied from coating thickness and speed.With the increase of coating thickness,the square resistance and transmittance of the film decrease,and the haze increases.When the coating thickness is 10μm,the photoelectric performance of the film is the best.With the increase of coating speed,the square resistance and transmittance of the film increase first and then decrease.The haze decreases first and then increases.When the coating speed is 25 cm/min,the film has the best photoelectric performance.In order to solve the problem of poor photoelectric properties of AgNWs-TCFs prepared by coating,present topic mainly focuses on improving the photoelectric properties of films by improving transmittance and reducing square resistance.By reducing the diameter of silver wire and purifying silver wire slurry,the transmittance of the film is improved.With the increase of drying temperature,the transmittance and haze of the film do not change significantly,but its conductivity increase obviously.When the drying temperature is 110°C,the resistance reduction rate is the largest,about 80.1%.Humidity also affects the conductivity of the film.When the humidity is 90%,the maximum resistance reduction rate is 80.5%.The AgNWs-TCFs with a size of20×20 cm²,a square resistance of 100Ω/sq,a transmittance（wavelength at 550 nm）of 91.8%,and a haze of 1.23%（including the substrate）are prepared succesfuly.