What They Said
We spoke with Stephan Kirchmeyer, head of the Display & Semiconductor Business Unit at Heraeus Clevios (client registration required) about its recent 55-inch diagonal touch-screen demonstrator with its fabless touch panel chip partner Inputek. The touch panel uses 200 nm thick, 150 Ω/sq PEDOT:PSS films with 90% transparency, not including the polyethylene terephthalate (PET) substrate. Stephen said that while 150 Ω/sq is traditionally not conductive enough for a large area touch screens, the Inputek chip has sufficient signal-to-noise ratio to produce a capacitive touch panel from such a film. He added that the touch panels are not ready for mass production and just meant to demonstrate the feasibility of using PEDOT:PSS in large-area touch screens. It will also announce demonstrators of flexible touch screens using its partner ITRI‘s flexible organic light-emitting diode (OLED) displays.
In addition to touch screens (and flexible touch screens), it targets flexible OLED, organic photovoltaic (OPV), and anti-counterfeiting smart packaging applications. Stephan said it has established PEDOT:PSS businesses in display anti-static films and in the counter electrode of polymer capacitors, and it is already used in a few touch screens including some smart watches and a GPS device. As a result, there is less urgency to bring its materials to market in nascent markets like flexible displays. However, Stephan said according to display OEMs roadmaps, he anticipates the first flexible display pilot lines coming online in 2015 and becoming mainstream in late 2015 or 2016, with clamshell smartphones – smartphones that have two half displays that open into a large, full display – being the first products to use them.
Stephan said the blue color of PEDOT:PSS is not a big problem, as the display panel can be tuned to offset the visual impact. The biggest issue in a touch screen is that patterned PEDOT:PSS creates an uneven visual experience, so Heraeus developed a process for making PEDOT:PSS non-conductive instead of actually removing it to pattern it for a touch screen, as would be done in ITO-based touch screens. In order to achieve this, it takes a PEDOT:PSS film, screen prints a mask (for resolutions 100 μm or higher resolution) or photolithography and the masked film is etched to make the exposed portions resistive.
Compared to ITO and emerging ITO replacements like silver nanowires and nanoparticles, Stephan said that PEDOT:PSS will differentiate on mechanical properties (flexibility and stretchability) and cost. He said a 150 Ω/sq film with 90% transparency costs 70% of the ITO price from Nitto Denko, which currently costs $23/m2 (although Stephan added that Nitto Denko’s prices have come down from $40/m2 in 2012). Heraeus sells PEDOT:PSS to customers, including Kodak, SKC, and Denshikako, which formulate it into inks and coat into films and sell them to the touch module manufacturers. Heraeus also plans to sell its etching materials to the module manufacturers. It plans to partner throughout the touch panel value chain and in each region of touch panel manufacturing, such as its recent partnership with Toagosei, which has expertise in ITO etching.
What We Think
Heraeus is fortunate to have its established PEDOT:PSS business, because it will not find significant revenues from flexible display touch screens in the time it anticipates. Flexible OLEDs, which would be the technology used in the proposed clamshell smartphones, only amount to a $21 million market in 2017 due to technical limitations, particularly in barrier film and high mobility, flexible thin-film transistors (TFTs, see the report “Cutting Up the LCD Pie: Calculating the Billion-Dollar Slices from Display Innovation” — client registration required). Even Novaled, which develops flexible OLED displays with partner Plastic Logic (client registration required), only anticipates flexible OLED demonstrators (client registration required), with performance comparable to todays rigid OLEDs, in 2016. Heraeus’ PEDOT:PSS will be a good technical fit for flexible and stretchable touch screens, but expect the market for flexible and stretchable touch screens to take longer to develop than it anticipates from display OEMs’ road maps.