Carbon‐nanotube film on plastic as transparent electrode for resistive touch screens

Abstract

Abstract— Carbon‐nanotube (CNT) films on plastic are incorporated as the touch electrode in a four‐wire resistive touch panel. Single‐point actuation tests show superior mechanical performance to ITO touch electrodes, with no loss of device functionality up to 3 million actuations. Sliding‐stylus‐pen tests reveal no loss of device linearity after 1 million stylus cycles. A CNT refractive index of ∼1.55 leads to CNT touch panels with low reflection (<9% over the visible range) without costly anti‐reflective coatings. CNT films on PET currently have 86% total transmission (including the PET) over the visible and 600 Ω/□, with lab scale tests giving 88% at 500 Ω/□. CNT films are neutrally colored (a * ∼ 0, b * ∼ 1.5), low haze (<1%), uniform, and both chemically and environmentally stable. Unidym's solution‐based coatings can be printed directly onto both flexible and rigid polycarbonate using solution coating processes. Unidym films can be patterned using subtractive methods such as laser ablation with resolution down to 10 μm, or additive methods such as patterned gravure. CNTs are grown, purified, formulated into inks, and coated using scalable processes, allowing films to be attractive from a cost perspective as well.

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