HOPV12 - Blogs

4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 257
C120 - Conductive surfaces on coated papers by flexographical printing
Dimitar Valtakari a , Roger Bollström a , Mikko Tuominen b , Hannu Teisala b , Mikko Aromaa c , Martti
Toivakka a , Jurkka Kuusipalo b , Jyrki M. Mäkelä c , Jun Uozumi d , Jarkko J. Saarinen a
a, Laboratory of Paper Coating and Converting, Åbo Akademi, Porthaninkatu 3-5, Turku, FI-20500, Finland
b, Paper Converting and Packaging Technology, Tampere University of Technology, Tampere, Finland
c, Aerosol Physics Laboratory, Institute of Physics, Tampere University of Technology, Tampere, Finland
d, Faculty of Engineering, Hokkai-Gakuen University, Sapporo, Japan
Printed electronics and intelligence have been under a growing interest since the start of
the 21 st century. Conventionally such applications have been produced on plastic films and
glass. However, paper based electronics (1) has been studied recently, and it has been shown
that simple, all-printed transistors can be made on multilayer coated paper (2). Paper has
many advantages over the plastic films: it is made of renewable materials and it is cheap with
tailorable surface properties.
Our study concentrates on using flexographical printing with conductive inks, PEDOT:PSS or
silver, on various coated paper grades to form large area conductive surfaces. Such conductive
surfaces are needed, for example, in electrochromic displays and in solar cells. We use two
different natural fibre based substrates: a multilayer pigment coated grade and a nanoparticle
coated paperboard in comparison to traditional plastic film. The paperboard surface is
functionalized by TiO2nanoparticles using a liquid flame spray (LFS) coating process.
In LFS process liquid precursor of titanium (IV) isopropoxide (TTIP) is fed into a high
temperature and velocity flame in which the metal salt evaporates and nucleates to form
nanoparticles of the metal oxide. These nanoparticles can be collected on a paperboard
surface in on-line process flow and they cover the whole surface passing under the flame (3).
It is known (4) that ultraviolet (UV) illumination can be used to change the wettability of
TiO2surfaces, and similar photocatalytic wettability conversion has been observed on
TiO2nanoparticle coated paperboard surfaces from superhydrophobic (water contact angle
(CA) over 150°) to superhydrophilic (water CA less than 20°).
Figure 1 Microscopic images of the flexographical Ag prints with 9 ml/m2 and 100 lines/cm (magnification 100x).
Here we report the effects of coating structure and surface wettability on formation of
conductive surfaces. Tunable wettability of TiO2nanoparticle coated substrates has an effect
on printability with water-based inks such as PEDOT:PSS as ink setting is poorer on
superhydrophobic surface that is also observed from measured optical densities of the printed
layers. We also report significantly higher conductivities with Ag ink on multilayer coated
paper than with PEDOT:PSS conductive polymer.
Acknowledgements: This work has been funded by the Academy of Finland (grant no
250 122 & 256 263). JJS wishes to thank the Japanese Society for the Promotion of Science
(JSPS) for a research grant (L-11537).We also wish to acknowledge Imerys Minerals Ltd., UK,
© SEFIN 2012