This month we are highlighting research extracts from our QUBE Automotive Glazing sector intelligence service ahead of an automotive glazing webinar scheduled for July 10. These extracts look at panoramic roofs and switcheable glazing.

Panoramic roofs

Saint-Gobain Sekurit points out that, in the early 1980s, the average surface area of glass in a car was approximately 3 m². This figure has risen to 4.5 m². Today, says the glass maker, more than 30% of the surface area of a vehicle consists of glass, adding: “The clear view up to the sky, feeling of freedom and large amount of light are the key selling points to consumers, who are spending an increasing amount of time in their vehicles.”

Peugeot was one of the first manufacturers to opt for a panoramic roof on a large scale in the 307 SW estate car. The vehicle maker currently offers this style of roof on a range of its models. The Citroën C4 has the largest glazed roof in its class (7.55 m² in total with 2 m² accounted for by the panoramic windshield). Compared with the Citroën Xsara Picasso model, which itself carries 6.67 m² of glass, an additional 13.2% of glass has been added to the C4 Picasso.

Saint-Gobain Sekurit supplies a variety of panoramic roofs ranging from the closed, large-area glass roof (Peugeot 307 SW, 407 SW and Citroën C4) to the so-called twin panels fitted to the Renault Espace IV through to the lamella sunroof fitted to the Fiat Stilo.

While panoramic roofs have some clear advantages for the vehicle occupants, the flipside is that replacing a sound-insulating roof with glass panels may result in unwanted heightened noise levels. An auto executive told us: “I believe that you would actually get quieter performance levels from the laminate than you would from the steel roof. OEMs are doing some specific treatment to the steel to make it quieter through various insulations. The car manufacturers actually find that adding a laminated glass does, in fact, improve their acoustics. But a lot of that comes from replacing a tempered piece of glass with a laminate. So the noise pick-up from something going over a roof versus a windshield is not as much as it would be for the windshield. The wind noise comes more from the vehicle’s windshield than from the sidelites or the roof.”

Switchable glazing

For some time, scientists and researchers have tried to develop a glazing system which would allow the consumer to change the level of light transmission in a vehicle. This technology would be mainly applicable for roofs and dark tail. This electrochromic functionality has been available for some time in building applications but was limited to an on/off system, switching the glass from transparent to translucent white. For cars, the ideal system would require the following:

  • the ability to choose the level of light transmission;
  • a short switching time;
  • a dark colour;
  • clear when powered and dark when switched off (parking conditions).

As the technology evolves and matures, we could expect to see this becoming popular and cheaper. At the 2009 Frankfurt motor show, Pilkington announced that it had acquired a new licence from Research Frontiers Inc. For some time, Research Frontiers has developed light-control film using suspended particle device (SPD) technology. In 2004, Pilkington acquired a licence from Research Frontiers to work with SPD technology to make laminated SPD-SmartGlass panels. With this new licence, Pilkington now has the ability to offer SPD-Smart end-products including sunroofs, glass roof panels, adaptive sun visors incorporated into a vehicle’s windshield, and side and rear windows. Anthony Shaw, vice president of automotive technology for Pilkington, said: “Our SPD teams in the UK, Germany, Japan and the US have been working with Research Frontiers and our lead OEM customer to introduce SPD-Smart end-products to the global automotive market…We see exciting opportunities ahead in the very near future.”

The 2012 model year Mercedes-Benz SLK will offer a so-called Magic Sky Control roof which can adjust the amount of light flooding into the cabin by pressing a switch. Particles in the glass position allow light to pass through when electricity current is passed through the roof structure but when the current is switched off, they adopt random positions, which blocks the passage of light. Mercedes says Magic Sky Control will be offered as an option costing less than EUR 2,000 when the next SLK goes on sale. In February 2011, Daimler confirmed that it is using Research Frontiers’ SPD-Smart light-control technology for its Magic Sky Control panoramic glass  roof, which appeared in the newly designed Mercedes-Benz SLK  during summer 2011.

More on the exclusive and free-to-access glazing webinar scheduled for July 10 

More reading: June 2012 management briefing: QUBE Automotive Glazing (heated windshields)