Transparent conducting coatings on polymer substrates for touchscreens and displays

Abstract

There has been an interest in using polymer films as an alternative to glass substrates and so this section should be viewed as being complementary to the chapters "{black right-pointing small triangle}Indium Tin Oxide (ITO): Sputter Deposition Processes," "{black right-pointing small triangle}ITO Replacements: Carbon Nanotubes," "{black right-pointing small triangle}ITO Replacements: Polymers Indium Tin Oxide (ITO)," and "{black right-pointing small triangle}ITO Replacements: Insulator-Metal-Insulator Layers” that cover coatings onto glass substrates. The polymer substrates have the potential to reduce the manufacturing costs by using roll-to-roll processing. The polymer also has improved flexibility, making the final display more robust to accidental damage and reduces the weight of the final product. Many touchscreens are constructions where two transparent conducting coatings are placed facing each other but separated by an array of small spacer dots. As one of the transparent coated films is pressed and distorted it contacts the other conducting film making electrical contact and completing the circuit. Thus having a robust transparent conducting coating on a flexible polymer substrate has a ready-made market so long as it can meet the required specification. The polymers have to be coated at a lower temperature than glass making the transparent conducting coatings less conducting or transparent than can be achieved on glass and so there is a trade-off of properties. As the coating performance improves and the yield and costs reduce the move to polymer substrates is expected to increase. This chapter highlights the basics of vacuum deposition of transparent conducting coatings onto polymer substrates.