Page 45

EETE JUN 2015

was very challenging because the previous process required the use of conductive fillers. However, adding these fillers modified the mechanical properties of polycarbonate and its transparency, and, in addition, the process was very complex. By contrast, rather than adding fillers, nanoparticle technology is wet coated or transferred onto polycarbonate film, offering a simple way to achieve a conductive polycarbonate material that is highly transparent, lightweight, flexible and highly formable. The nanoparticle conductive coating comes in a wet dispersion form. The dispersion is then emulsified and coated onto the polycarbonate substrate; the emulsion evaporates under ambient conditions, and within seconds, the silver nanoparticles come together forming agglomerated, interconnected, micronsize lines with a dense array of random micron-scale pores that allow the whole wavelength of light to pass through with little attenuation. In addition to its potential performance capabilities in large format displays, another area where this solution stands apart is in its ability to be thermoformed into complex 2.5 or 3D shapes, such as those required for a variety of displays in consumer electronics, automotive interiors and healthcare devices, as well as architectural. 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 advanced materials such as transparent, conductive polycarbonate film, the opportunity exists 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 touchenabled sensors for navigation and infotainment without compromising the self-capacitive capability for climate controls. Another benefit of the transparent, conductive polycarbonate solution is its sensitivity, which can bring the response times of small size touchscreens to large format touchscreens. The material is capable of 10 ohm/m2 (compared to ITO, which is > 100 ohm/m2) and in fact, a 100” demonstration touchscreen display (this one, created using PET because curvature was not required) has been created that delivers real time response. And, when compared to ITO laminates over a glass substrate, the transparent, conductive polycarbonate film – available in gauges from 800 micrometers to 125 microns – provides considerable weight savings, which can support thin wall designs as well as potentially reduce transportation costs. A more cost effective alternative The manufacturing process for transparent, conductive polycarbonate film is simple, using a roll-to-roll process versus sheet-to-sheet processing. The roll-to-roll process is a coating process that can be applied to thin gauge structures with high speed manufacturing, with the ability to continuously coat wide width rolls in thousands of meters. Sheet-to-sheet manufacturing is a batch process, involving coating film sheet-by-sheet in dimensions smaller than in roll form. Because more labor is required, system costs are typically higher for sheet-to-sheet than roll-to-roll processing. Clearly, different materials can provide benefits for different display needs. However, when design is important, only one material is capable of delivering excellent transparency, conductivity resistivity and formability: polycarbonate. LCD touch displays roll to a 12.5cm radius Varitronix is now makes flexible LCD displays that accept a curve with a radius as tight as 12.5cm, manufactured in small sizes, similar to that of a credit card. The flexibility is due to the innovative manufacturing process that Varitronix uses, with a total display thickness of 0.56mm. This extremely thin design also makes the displays very light. The company claims that providing the curvature specifications are not exceeded, its displays are virtually unbreakable. The Ultra-Flexible LCD Displays use Segmented Monochrome TN technology and have In-Cell touch capabilities. The displays have a wide operating temperature range of -10C to +60C, with a typical supply voltage of 5V. Display modes include transmissive, transflective and reflective and the inter-connection method is via heat seal FPC bonding. Varitronix UK www.varitronix.com PCB Prototypes & Small Series PCB Manufacturing from 8 hours FREE SMT stencil with EVERY Prototype order! sales@pcb-pool.com www.pcb-pool.com PCB-POOL® is a registered trademark of Beta LAYOUT GmbH www.electronics-eetimes.com Electronic Engineering Times Europe June 2015 37


EETE JUN 2015
To see the actual publication please follow the link above