Inkjet Printing of High Index Zirconia Nanocomposite Materials

M.D. Healy, P. Guschl, X. Wang, M. Weinstein
Pixelligent Technologies LLC,
United States

Keywords: inkjet, display, OLED, light extraction, optics, nanocomposite, microlens, refractive index, zirconia, diffraction, thin film, haze

Summary:

Abstract High refractive index (RI) nanocomposites have properties which surpass traditional polymers while maintaining manufacturability. Nanocrystal-polymer nanocomposites, when inkjet-printed, are useful to many display components and aid the development of next generation displays. This paper demonstrates inkjet printing capabilities using high RI, highly transparent PixClear® ZrO2 nanocrystal dispersions and inks. PixClear ZrO2 nanocomposites have already demonstrated increased light extraction (>100%) in OLED lighting devices [1]. The main benefit of PixClear materials is that they can dramatically increase the refractive index (RI) of monomers and polymers with ZrO2 content as high as 90 wt% while maintaining high transparency over the visible light spectrum [2]. With an efficient use of coating materials and the ability to place droplets on the micron-scale, inkjet printing can be used to create display components such as light extraction films/coatings, lenses, back lighting diffusers, barrier films, anti-reflective coatings, and index matching films [3][4][5]. We have successfully demonstrated inkjet printing of PixClear light extraction coatings and structures and will discuss the process for printing these layers as well as the optical results of printing nanocomposite films. An important property of formulations that are printable via inkjet is latency. In order to demonstrate the pot-life quality of our PixClear inks, films were printed at t = 0, 15, 60 and 300 minutes, by using the inks in a single cartridge. Figure 1 demonstrates the consistency of producing film thicknesses between 0.5 and 0.6 microns with film non-uniformities of less than 12%. We will demonstrate that PixClear inks with scattering particles can also be inkjet-printed as blanket films, patterns and structures for the purpose of improved light extraction in devices for OLED displays and OLED lighting. Inkjet-printed, optically clear films containing Pixelligent’s PixClear zirconia nanocrystals show excellent uniformity and are achievable with transparent high refractive index inks that can be printed with remarkable consistency (latency). Films comprising scattering particles in addition to the PixClear ZrO2 nanocrystals can be printed into various simple and complex patterns. Information from this paper gives strong support that these materials can be extremely useful as light extraction layers in a wide variety of display applications [6]. References [1] http://www.pixelligent.com/wp-content/files/2015/07/WP-OLED-ILE.pdf [2] http://www.pixelligent.com/wp-content/files/2015/07/WP-Pixelligent-Zirconia-Nanocrystals-for-OLED-Applications.pdf [3] M Singh, H Haverinen, H P Dhagat, and G E Jabbour, “Inkjet Printing—Process and Its Applications”, Adv. Mater., 22, 2010 [4] Tekin, Emine, Patrick J. Smith, and Ulrich S. Schubert. "Inkjet printing as a deposition and patterning tool for polymers and inorganic particles." Soft Matter 4.4 (2008): 703-713. [5] Tien, Chung-Hao, Chien-Hsiang Hung, and Tsung-Han Yu. "Microlens arrays by direct-writing inkjet print for LCD backlighting applications." Journal of display technology 5.5 (2009): 147-151. [6] de Gans, B‐J., Paul C. Duineveld, and Ulrich S. Schubert. "Inkjet printing of polymers: state of the art and future developments." Advanced materials16.3 (2004): 203-213. Prior Publications – Available on www.pixelligent.com