Kimmo Lahtinen

Roll-to-roll atomic layer deposition process for flexible electronics encapsulation applications

At present flexible electronic devices are under extensive development and, among them, flexible organic light-emitting diode displays are the closest to a large market deployment. One of the remaining unsolved challenges is high throughput production of impermeable flexible transparent barrier layers that protect sensitive light-emitting materials against ambient moisture. The present studies deal with the adaptation of the atomic layer deposition (ALD) process to high-throughput roll-to-roll production using the spatial ALD concept. We report the development of such a process for the deposition of 20 nm thickness Al2O3 diffusion barrier layers on 500 mm wide polymer webs. The process uses trimethylaluminum and water as precursors at a substrate temperature of 105 °C. The observation of self-limiting film growth behavior and uniformity of thickness confirms the ALD growth mechanism. Water vapor transmission rates for 20 nm Al2O3 films deposited on polyethylene naphthalate (PEN) substrates were measured a...

Influence of High-Temperature Heat Treatment on Barrier and Functional Properties of Polyolefin-Coated Papers

In this study, the effect of heat treatment on barrier and functionality of polyolefin-coated papers was investigated. The aim was to find the optimal improvements on barrier without losing the applicability of the materials due to physical damages. The results of the study proved considerable improvement in barrier characteristics of the structures. Both water vapor and oxygen transmission rates of LDPE-coatings decreased linearly following the set-temperature until 200°C. At this point, the treatment caused a continuing decrease in oxygen transmission achieving 10 × lower transmission levels than the untreated structure, whereas moisture transport faced corresponding but lower increase. This was considered to be caused by the difference in diameter of the H2O and O2 molecules; the smaller water molecules are able to penetrate between spherulites, whose size increased due to higher treatment temperature followed by cooling.

Influence of Temperature and Mixing Ratio on Water Vapor Barrier Properties of Extrusion-Coated Paper

Abstract When making food packages from fiber-based, extrusion-coated materials, water vapor transmission rate (WVTR) of the material is one of the key factors defining the shelf life of the product. The WVTR test is commonly a time-consuming procedure that delays progress in project development. In this study, a calculation method for WVTR-determinations was devised that can reduce the amount of testing and thus enhance the speed of research. Furthermore, the effect of atmospheric conditions on the permeation of water vapor through packaging materials is an important factor in view of the use of food packages all over the world. In this study, it was found that the combined effects of both relative humidity and temperature resulted in an almost linearly increasing WVTR as a function of mixing ratio under the given atmospheric conditions.