Design And Preparation Of New Flexible High Transparent Paper Material And Its Application Research

Flexible transparent substrate materials have been successfully applied in electronic devices such as organic light-emitting diodes, touch screens, and solar cells as they are low-cost, unbreakable, and flexible etc. Although plastic substrates have been used widely in flexible electronics, there are several disadvantages associated with plastic substrates, including a low processing temperature, a large coefficient of thermal expansion, poor printability and recyclability, which leads to some difficulties and challenges to assemble precise electronic circuits or components on them. It’s the fundamental reason for the slow development of the plastic substrates. Natural wood fibers, the porous and anisotropic biopolymer, have huge potential in flexible transparent substrate material field, due to their quintessential properties such as non-pollution, low cost, and abundant in source. In this paper, we introduced three new methods to prepare new flexible transparent paper materials, and further investigated their fabrication mechanisms and applications.(1) Rapid “dessolving-debonding” strategy for optically transparent paper production. The raw cellulose fibers were firstly fully dissolved in the ionic liquid, and the obtained cellulose solution was then added dropwise into the regenerative solution with high-speed emulsification to prepare the microsized regenerative cellulose fibers(RCFs). Transparent paper was formed by vacuum filtration of RCFs suspension. It was found that the RCF transparent paper has a total optical transmittance of 91.5 % and optical haze of 48 % at a wavenlength of 550 nm. The fabrication time of transparent paper was only 30 min which was much shorter than that of preparing highly transparent nanopaper.(2) “Partial dissolution” strategy to fabricate cellulose nanofibers and highly transparent nanopaper. The basification of cellulose fibers was firstly carried out by treatment in anhydrous NaOH/Dimethyl sulfoxide(DMSO), and then secondary sodium acetoxylation of the basified cellulose fibers in anhydrous ClCH2COONa/DMSO was performed to introduce –CH2COONa groups onto the cellulose chain. The part formation of water-soluble sodium carboxymethyl cellulose(CMC) from cellulose, and further dissolution of them from cellulose collapses the cell wall of cellulose during a water washing process. It was demonstrated that cellulose nanofiber yield was high to 56.5 %, and an important chemical of CMC was harvested. The nanopaper possesses a total optical transmittance of 90.5 % at a wavelength of 550 nm, and exhibits an outstanding tensile strength of about 100 MPa. Otherwise, the surface roughness of nanopaper is 15.3 nm(Rq) and 12.2 nm(Ra).(3) “Situ-devillicate and nanowelding” for high transparent cellulose paper preparation. The regular paper was invaded by ILs and hot-pressed to facilitate devillicate and nanowelding of cellulose fibers. Ethanol was finally used to wash out residual ILs. It was investigated that cellulose paper not only possesses high transparency(91 %, 550 nm) and optical haze(89 %, 550 nm), but also a low surface roughness of 4.03 nm(Rq) and 3.13 nm(Ra). The excellent optical haze of cellulose paper lays a good foundation for its application in solar cells.This thesis finally explored the application of new transparent paper materials in electronic devices. Silver nanowire was directly deposited on nanopaper by vacuum filtration to fabricate conductive nanopaper. It was found that conducive nanopaper from silver nanowire concentration of 15.9 mg/m2 possesses excellent conductivity(26.2Ω/ sq) and transparency(86.5%, 550 nm),its photoelectric property was superior to the similar flexible transparent conductive films substrates.