INNOVATION | LIQUID SILICONE RUBBER
Above:
Exploded view of Hella’s Matrix HD84 LED headlamp with LSR light guide in
primary optic component on left
optics. Each LED can be switched on or off to create the different lighting functions. Car lighting designers like the light transmission performance of LSR, which is better than PC, PMMA and glass, he said. LSR’s refractive index is accept- able in comparison with other materials. Material selection is dependent on the complexity required in the headlamp’s primary optics. He said: “We won’t use silicone material if we are able to use thermoplastics or glass. But if glass can’t be used because, for example, of the complexity of the part, and thermoplastics can’t be used because of the heat resistance and energy resistance next to the white LED, we say yes to LSR for primary optics.” In answer to a question on whether LSR’s higher cost is an obstacle for Hella, he said comparisons should not be made directly between material costs, but should be done on the basis of complete costs for the headlamp. “If we must use LSR for technical reasons, then we do this,” he said. The innovation possibilities of LSR in car interior lighting were discussed by Bernhard Mitteregger, Sales Manager at Silcos. “Illumination is standard in a car but innovation is using LSR to make surfaces flexible,” said Mitteregger. Silcos is a silicones specialist that predominantly manufactures for the automotive sector. Ambient lighting in car interiors is a target area for its LSR business. The company has developed Siloptics Flexilight, a flexible light guide, which consists of a flat silicone body, the dimensions of which are adjustable up to a maximum size of 500 x 300 mm. The construction combines reflector, light guide and decorated diffuser. The lighting in Siloptics Flexilight comes from LEDs housed on a small board in the edge. Homogeneous illumination over the entire length is achieved with the highly transparent LSR core serving as a light guide. The product depth is small and is easy to clean, with low dirt and dust adhe- sion, says Silcos. “In order to decouple the light
16 INJECTION WORLD | April 2020
evenly over the entire surface, the light conducting, highly transparent silicone core of the Siloptics Flexilight is printed with a previously calculated structure. This structure is finer the closer it is to the light source and becomes larger the further it moves away from the light source. As a result, the Flexilight glows uniformly over the entire surface.” Mitteregger said the company has been discussing with car designers about the possible applications for the Siloptics Flexilight technology. In car interiors, interest is focusing on the technol- ogy’s possible integration with materials including plastics, leather and fabric. Its flexibility makes it a candidate for use on curved surfaces. He said exterior applications are also being
investigated. These include pedestrian protection possibilities, for example, by integrating Flexilight in the “grille” area of electric vehicles, which are being transformed by new lighting design. For Wacker, electrification of vehicles is a trend
with great potential, said Udo Wachtler, Technical Manager for Engineering Silicones, at the confer- ence. He said that by 2025, EVs and hybrid cars are expected to have on average 10,000 metres of cabling, 3,000 connections and multiple power supplies from 12V and 48V up to 800V. “Automo- tive megatrends are pushing material selection towards silicone elastomers,” said Wachtler. In EVs, high voltage insulating materials are
required for cables and connectors. LSR is suited to these applications because of high temperature resistance and low thermal conductivity. For example, in a fast-charger, cables become very hot, so LSR helps manage the heat, he said. In combus- tion engines, the downsizing trend is leading to higher operating temperatures. Here, more heat-resistant materials are needed in connectors, gaskets and other applications.
Silcos developed Siloptics Flexilight, a flexible light guide with a flat silicone core, for ambient car lighting
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IMAGE: HELLA
IMAGE: SILCOS
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