Thermoformable polycarbonate film for large format touch screens

• Film can be thermoformed into complex 2.5 or 3D shapes
• Polycarbonate more sensitive than other alternatives on the market
• Advantages over conductive polyethylene terephthalate (PET)
• Considerable weight savings over tin oxide (ITO)-based glass solutions
• Promising application: center display stack (CSD) for automotive interiors

SABIC has introduced a transparent, conductive polycarbonate (PC) film that represents a completely new class of display materials with exceptional transmittance and resistance, especially in large formats, with good 2.5 and 3D formability.. The film combines Sante nanoparticle technology from Cima NanoTech over a substrate of SABIC’s Lexan film to achieve highly sensitive touch screens that are also impact resistant and formable. Due to its ability to be thermoformed into complex 2.5 or 3D shapes, the film can also be used for a variety of displays in consumer electronics, automotive interiors and healthcare devices.

“With the need for information to be constantly at our fingertips, the challenge becomes how to integrate touch screen functionality into spaces where design and aesthetics are also important – such as in an automotive interior or wearable technology – or where extremely large format touch screens are required, such as digital signage or electronic white boards. Other challenges include transparency and, of course, cost containment wherever possible,” Alan Tsai, Director, Technology & Innovation for Display & Electronics, noted.

Polycarbonate more sensitive than other alternatives on the market

There are alternatives on the market today, such as indium tin oxide (ITO)-based solutions over a glass substrate and conductive polyethylene terephthalate (PET). SABIC’s polycarbonate solution has advantages over both, according to the company. First, the transparent, conductive polycarbonate solution is more sensitive, which can bring the response times of small size touchscreens to large format touchscreens. The material is capable of 20 ohm/m2 (compared to ITO, which is > 100 ohm/m2).

Considerable weight savings over tin oxide (ITO)-based glass solutions

Compared to ITO laminates over a glass substrate, the transparent, conductive polycarbonate film, available in gauges from 800 micrometers to 125 micrometers, provides considerable weight savings, which can support thin wall designs as well as potentially reduce transportation costs. Another key advantage is formability: the use of ITO is challenging when considered for flexible touch screens due to its brittle nature. When flexed, ITO will crack, thus preventing the operation of the touchscreen.

Advantages over conductive polyethylene terephthalate (PET)

PET-based solutions are also often considered. However, when compared to the polycarbonate film solution, its resistance is relatively high (>150 Ω/m2) and the material exhibits lower conductivity. PET lacks the rigidity and impact resistance properties of polycarbonate, creating challenges when attempting to achieve large format displays. It, too, exhibits only average formability because PET is not capable of withstanding the higher temperatures needed to thermoform the material into complex designs.

Promising application: center display stack (CSD) for automotive interiors

A case in point is center display stack (CSD) for automotive interiors, which typically includes touchscreens for navigation, infotainment features and back-up cameras as well as an area for climate control. With transparent, conductive polycarbonate film it is possible to create an integrated CSD design to consolidate these controls in one unit. Conductive PC film can achieve the forms and curvatures typical for center display units with multiple touch-enabled sensors for navigation and infotainment without compromising the self-capacitive capability for climate controls.

SABIC has made available large scale samples of its transparent conductive PC film in either sheet or roll form with web width up to 1.2 meters for use in customer trials, with commercial scale quantities available in the second half of this year.