Perhydropolysilazane derived silica for flexible transparent barrier foils using a reel-to-reel wet coating technique: Single- and multilayer structures

The paper concerns investigations of the coating and the converting conditions of perhydropolysilazane (PHPS) for the creation of SiOx including multilayer setups for application in transparent gas barrier foils. The use of different substrates and several organic intercalated layers was proofed also in reel-to-reel (R2R) coating processes. A lowering of the gas permeation against oxygen and water could be found for the coated foils under maintaining the optical transparency of the pristine foils. With one SiOx layer (600 nm) coated by R2R and converted at low temperature a reduction of the oxygen transmission rate (OTR) from 11 cm3/(m2 d bar) of pure 125 μm polyethylene terephthalate (PET) to 0.09 cm3/(m2 d bar) of PET/SiOx could be observed. Taking advantage of the so-called “tortuous path effect”, we obtained OTR values below 0.05 cm3/(m2 d bar) (detection limit of the Mocon test) with 3- or 5-layer-systems. The films are highly optically transparent and can exceed the light transmission of the uncoated substrate using an optimized layer stack with respect to thickness and refractive index.