Cracked ITO on Polyester Film Substrates for Electro-Optic Applications

Abstract:

Vacuum deposited indium tin oxide, ITO, is the material of choice for producing the transparent conducting electrodes used in a wide variety of electro-optic applications, including flat panel displays and solar cells. In addition to rigid substrates such as glass, ITO can be coated on flexible substrates for the production of flexible devices. Because the ITO is brittle it easily cracks if the flexible substrates are bent. The cracking of the ITO is therefore viewed within the industry as a major problem. Here we demonstrate how we can control the cracking of the ITO to produce uniform electrodes. This is accomplished by bending the film around a tight radius of curvature. The electrodes are narrow having a width of 5~10 μm. The cracks separating the electrodes are much narrower with a width of less than 0.05 μm. We demonstrate the use of these substrates using a polymer dispersed liquid crystal switchable window that can be switched in individual lines creating an electronic venetian blind effect. The addressed lines in the PDLC are defined by the contact electrode and by the applied field. Because the cracks are much smaller than the thickness of the active PDLC material they are not visible. In addition to switchable windows these substrates can be used to make passive matrix displays and touch screens. Uni-axially cracking can be easily integrated into a roll-to-roll manufacturing process.

• Periodical: Applied Mechanics and Materials (Volume 526)
• Pages: 15-20
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.526.15
• Online since: February 2014
• Authors: John L. West, Da Wei Lee
• Keywords: Flat Panel Displays, Indium Tin Oxide (ITO), Liquid Crystals, Transparent Conducting Substrates

References

[1] Lawrence Gasman: Transcript from NanoMarkets Q&A on Transparent Conductors, September 2012, commenting on the Transparent Conductor Markets 2012 Report by NanoMarkets, August, (2012).

[2] A. L. Volynskii, S. Bazhenov, O. V. Lebedeva, A.N. Ozerin and N.F. Bakeev, Multiple Cracking of Rigid Platinum Film Covering Polymer Substrate, Journal of Applied Polymer Science, Vol. 72, p.1267, (1999).

DOI: 10.1002/(sici)1097-4628(19990606)72:10<1267::aid-app5>3.0.co;2-3

[3] D. R. Cairns, and C. P Crawford, Electromechanical Properties of Transparent Conducting Substrates for Flexible Electronic Display, Proceedings of the IEEE, Vol. 93, No. 8, p.1451, (2005).

DOI: 10.1109/jproc.2005.851515

[4] T. Königer, and H. Munstedt, Advanced device for testing the electrical behavior of conductive coatings on flexible polymer substrates under oscillatory bending: comparison of coatings of sputtered indium-tin oxide and poly3, 4ethylenedioxythiophene, Measurement Science and Technology, 19, 055709, (2008).

DOI: 10.1088/0957-0233/19/5/055709

[5] J. L. West, M. Cakmak, T. -M. Huang and D. -W. Lee, Uniaxially Cracked ITO on PET Substrate and its Application in Flexible Displays, SID Symposium Digest of Technical Papers, 43, 1368-71, (2012).

DOI: 10.1002/j.2168-0159.2012.tb06059.x

[6] J. L. West, M. Cakmak, T. -M. Huang and D. -W. Lee, Uni-axial Cracking of ITO to Form Row and Column Electrodes for Roll to Roll Production of Flexible Displays and Electronics, MRS Proceedings, 1529 mrsf12-1529-ww04-02 doi: 10. 1557. 2013. 288.

DOI: 10.1557/opl.2013.288

[7] J. L. West, Polymer-Dispersed Liquid Crystals, in Progress in Liquid Crystal Science and Technology, Series on Liquid Crystals, Vol. 4, 575-596, World Scientific Publishing, (2013).

DOI: 10.1142/9789814417600_0025