Flexible electronic devices such as organic Photovoltaics or OLED displays require encapsulation envelopes with extreme gas permeation barrier properties to achieve the required life time stability1.
A low cost manufacturing process for gas permeation barrier foils remains a critical success factor for massive market introduction of flexible electronic devices.
PECVD processing under atmospheric pressure is a technology with great promises, but the gas moisture barriers produced with this technology were not adequate for flexible electronic applications2 3. Fujifilm recently developed a next generation of atmospheric PECVD technology4 and succeeded to use this new technology for the production of high quality moisture barrier films on PET foil.
A roll-to-roll atmospheric pressure PECVD reactor
The novel atmospheric plasma reactor consists of a dielectric barrier discharge (DBD) plasma, ignited between two rotary drum electrodes that are covered by a transparent PET foil, transported through the reactor with a constant speed.
The PET foil serves as the functional dielectric barrier material in the reactor space and at the same time as the product on which the silica-like barrier is deposited (see figure 1). This specific design of the plasma reactor results in a 100% precursor-to-product ratio, absence of parasite depositions and control of the processing temperature by the intimate contact between the PET foil and the T-controlled drum electrode in the plasma space.
The atmospheric pressure PECVD process is open to ambient air, has an excellent scale-ability (up to 200 cm treatment width), and is characterised by low investment and operational costs (CAPEX / OPEX). The freedom to integration this atmospheric pressure PECVD process with additional cleaning, surface pre-treatment and wet coating steps is an important prerequisite of the developed technology platform.
While high power densities of more than 30 W/cm2 are obtained, filamentary discharges are fully prevented by use of proprietary electronic stabilisation methods, preventing the glow to arc transition that is typical for traditional atmospheric corona-type plasma discharges5.
Fig 1, The layout of the Fujifilm DBD plasma reactor
The performance of Fujifilm's atmospheric pressure PECVD process.
Fujifilm engineers developed a process for the deposition of defect-free silica layers with use of this atmospheric pressure PECVD. The developed ultra-thin silica-based barrier layers show a WVTR of 10-4 gr/m2 day.
The deposition process is characterised by a conformal layer growth (see fig 2), with ALD-like quality and well suited for manufacturing of stacked multi-layer barrier structures with a WVTR of 10-6 gr/m2 day, as required for OLED applications.
Fig. 2, Surface morphology of the a) pristine PEN substrate Rq = 1.1±0.1 nm, b) 70 nm thick silica-like film deposited on PEN Rq = 1.1±0.3 nm
As the substrate temperature in the ambient air plasma reactor is kept below 110 °C, this process was proven to be adequate for deposition of barrier coatings on polymeric foils with a low Tg, like PET. The process has been developed up to pilot plant scale (see fig. 3), to demonstrate it's suitability for large scale manufacturing.
Fig.3, The atmospheric pressure DBD plasma facility for production of ultra-barrier foils at pilot plant scale.
Opportunity for partners of Fujifilm
Fujifilm is open for partnerships to explore this in-house developed technology for commercial use by tech-transfer, licensing out and collaborative product development programs. For more information look at: www.green-plasma.eu or contact Jan Bouwstra (email@example.com).
1 N. Grossiord, J.M. Kroon, R. Andriessen, P.W.M. Blom, Org. Electron. 2012, 13, 432.
2 P. Scopece, A. Viaro, R. Sulcis, I. Kulyk, A. Patelli, M. Guglielmi, Plasma Process. Polym. 2009, 6, S705.
3 J. Petersen, J. Bardon, A. Dinia, D. Ruch, N. Gherardi, ACS Appl Mater. Interphases 2012, 4, 5872
4 S.A. Starostin, M.C. Creatore, J.B. Bouwstra, M.C.M. van de Sanden, H.W de Vries, Plasma Process. Polym. 2015, 6, S503,
5 S.A.Starostin, P. Anthony Premkumar, M. Creatore, E.M. van Veldhuizen, H. de Vries, R.M.J. Paffen, M.C.M. van de Sanden, Plasma Sources Sci. Technol. 2009, 71, 417.