Touch functionality on curved surfaces

Fürth/Germany, 9 October 2013: At K 2013, the company Leonhard Kurz will be demonstrating, for the first time ever, a 3D plastic part being decorated while concurrently having touch functions integrated into it. Visitors to the Kurz booth will be able to see, live in action, a Duo 400 injection molding machine from Engel Austria producing the front panel of a curved automotive center console in a single work operation while also equipping it with two separate touch functions: touchkeys, slides and a wheel in the upper area of the console, and a touchpad in the lower area. The component will be produced in an integrated process combining Inmold Decoration (IMD) and Inmold Labeling (IML), whereby the decorative coating, including UV top coat, is applied to the front face of the panel in the IMD transfer process, and the touch functions are integrated into two separate Inmold labels that are fused to the rear of the component. "The market is calling for surfaces that are decorative, functional and durable, all at the same time - and able to be produced highly efficiently as well,” explains Martin Hahn, Product Manager at Kurz, as background for the development of this process. "Thanks to this innovative integrated process, we have succeeded in mastering this balancing act.”

Functional structures printed on a PET carrier

The sensor foils used for the single touch panel and the multi touch functionality were developed by the Kurz subsidiary PolyIC. These transparent, conductive functional foils called PolyTC® are equipped with extremely thin, conductive metal mesh structures. These structures are produced in a reel-to-reel process in which extremely thin metallic layers are applied to a PET substrate. Using transparent PET foils as the underlying substrate enables these PolyTC® sensors to be especially thin and flexible. Thanks to the advantageous mechanical properties of the carrier foil and the metal mesh structure, they are able to be processed by means of the IML process and are suitable for use on curved surfaces. This is a key advantage over the brittle ITO coating that has generally been used in the production of capacitive sensor elements in the past.

New design options and process advantages

The production cell that Kurz and PolyIC will be presenting, in conjunction with their die and machine manufacturing partners, not only opens up new interior design options for the automotive industry, but also many other potential applications in the areas of consumer electronics, displays or household appliances. It enables touch panels to be incorporated into the surface as a fully enclosed flat element that can be integrated harmoniously into the overall design. These controls, which have no switches, buttons or grooves, are not only visually appealing but also easy to clean and maintain. Since these components comprise only the sensor foil and the contact elements for the controller connection, they also save weight and space. The combined IMD and IML process offers economic advantages too. Producing a decorated injection molded part with integrated functionality in a single processing step significantly reduces the process cost. The controls can be linked to the vehicle electronics system quickly and efficiently simply by plugging the contact points into the controller. "In the end, it's the cost-effectiveness that Counts,” emphasizes Martin Hahn. "That's why we focused on efficiency criteria while developing the process in conjunction with our subsidiary PolyIC, our systems partner for decoration, sensor foil technologies, and the integration of these technologies. This principle applied equally well to the mold and machine concept as well as the application technology.”

As Hahn further explains, optimizing the parameter settings for the overall injection molding process is a very time-consuming task. "It requires meticulous adjustment of all influencing variables, for example the sensor layout, the IMD decor foil and the mold design - along with lots of experience! This kind of problem can only truly be solved by a single-source supplier. Series production has only been achievable, in this particular application, thanks to the combined know-how of Kurz and PolyIC,” says Hahn with conviction.

At the K trade fair, a near series-production capable, fully-automated production cell will be on display to demonstrate the economic viability of this integrated process. Visit the Kurz booth A19 in Hall 5 to see a live demonstration of this cost-effective production process.