Photochemically initiated coating technologies

We develop coating processes that include light-induced reactions (e.g. polymerizations or conversions). Organic, hybrid or inorganic layers can be applied to different, especially thermally sensitive substrates. The use of high-energy light in the (V)UV wavelength range as reaction initiator enables the realization of low process temperatures, the application at atmospheric pressure, and the control of layer properties. Fundamental investigations of electronic excitation mechanisms as well as analysis of the resulting materials enables the creation of parameter-effect relationships. Starting with feasibility studies, specific technologies for the use of these processes can be developed in cooperation with industrial partners and transferred to production-relevant processes.

Analytical methods comprise chemical composition, morphology and structure (XPS, ATR-IR, XRD, XRR, REM, UV-Vis), as well as application-relevant methods (e.g. gas permeation, scratch and abrasion resistance, bending tests). Various methods of (V)UV-induced modification of organic and inorganic substrates, e.g. of polymers, textile fibers and fabrics or metals, can be investigated.

 

Expertise

  • Roll to roll deposition of silicon(IV) oxide thin films for flexible transparent high barrier foils
  • Low temperature fabrication process for transparent flexible (conductive) layers
  • Roll-to-roll precision coatings with UV-curable coatings

Highlights

  • Flexible Transparent Barrier Applications of Oxide Thin Films Prepared by Photochemical Conversion at Low Temperature and Ambient Pressure

    P.C. With, U. Helmstedt, L. Prager
    Frontiers in Materials 7 (2020) 200
    https://doi.org/10.3389/fmats.2020.00200

    Photoconversion of organometallic precursors to thin metal oxide films is a powerful technology that has applications at temperatures < 80 °C and at normal pressure. This review article summarizes various aspects of the research and development. The article focuses on applications of the films as gas permeation barriers on polymer films for encapsulation of optoelectronic devices.

  • Conversion of perhydropolysilazane into a SiOx network triggered by vacuum ultraviolet irradiation: access to flexible, transparent barrier coatings

    Dr. L. Prager, Dr. A. Dierdorf , H. Liebe, Dr. S. Naumov, Dr. S. Stojanović , R. Heller, Dr. L. Wennrich , Prof. Dr. M. R. Buchmeiser
    Chem. Eur. J. 13 (2007) 8522–8529
    https://doi.org/10.1002/chem.200700351

    Photoconversion of polysilazanes opens up a simple route, feasible at room temperature and normal pressure, to generate functionalized silicon(IV) oxide-based coatings. This article includes, among other things, a kinetic consideration of the conversion as well as a theoretical consideration of the electronic excitation process.  

  • Vacuum-UV Irradiation-Based Formation of Methyl-Si-O-Si Networks from Poly(1,1-Dimethylsilazane-co-1-methylsilazane)

    L. Prager, L. Wennrich, R. Heller, W. Knolle, S. Naumov, A. Prager, D. Decker, H. Liebe, M. R. Buchmeiser
    Chem. Eur. J. 15 (2009) 675–683
    DOI: 10.1002/chem.200801659

    Polysilazanes can be variously substituted and therefore provide a suitable class of materials for a range of functionalized coatings. In this article, both light-induced excitation and conversion mechanisms are investigated.

  • Low-temperature photochemical conversion of organometallic precursor layers to titanium(IV) oxide thin films

    P. C. With, U. Helmstedt, S. Naumov, A. Sobottka, A. Prager, U. Decker, R. Heller, B. Abel, L. Prager
    Chem. Mater. 28 (2016) 7715–7724
    https://doi.org/10.1021/acs.chemmater.6b02757

    This article demonstrates that VUV light induced conversion reactions are suitable to produce dense closed and chemically pure titanium(IV) oxide thin films, also on polymer substrates. The conversion and removal of organics from the thin precursor films were investigated in more detail and proposals for a reaction mechanism based on experimental and theoretical consideration were presented.

  • Photochemical approach to high-barrier films for the encapsulation of flexible laminary electronic devices

    L. Prager, U. Helmstedt, H. Herrnberger, O. Kahle, F. Kita, M. Münch, A. Pender, A. Prager, J.W. Gerlach, M. Stasiak
    Thin Solid Films 570 (2014) 87–95
    DOI: 10.1016/j.tsf.2014.09.014

    Transparent barrier films are necessary to encapsulate e.g. flexible photovoltaics and thus protect them from degradation towards atmospheric oxygen and moisture. This article discusses the roll-to-roll coating of polymeric substrate films with a thin silicon(IV) oxide-based gas barrier layer. Among other things, it is demonstrated that the fabricated gas barrier films can withstand various climatic conditions and thus protect the sensitive active components of photovoltaics.