Malcolm Wheatley discovers that even after more than a century of development, the automotive glassmaking industry is still developing innovative technologies
Developments such as water-repellent and heat-reflective glass, in-built sensors, ‘headup displays’, and ultra-violet light-reflective glass are now regularly incorporated into windscreens installed during vehicle assembly.
Automotive glass is lighter, thinner and stronger than ever; it is formed to deliver enhanced structural strength and rigidity, while allowing designers more scope to turn the smoothly streamlined shapes on their drawing boards into real physical objects travelling down the assembly line.
“Plastics manufacturers talk about substituting plastics for glass in automotive applications, but the elephant in the room is that glass is phenomenally strong for its weight, so that it helps to reduce weight elsewhere in the vehicle,” says Dr Chris Davies, head of innovation and science at global aftermarket specialist Belron, which owns businesses such as the UK’s Autoglass. “In a like-for-like comparison on the same model, you’d have to either add more steel, or make the plastic much thicker.”
That’s before you consider developments such as ‘augmented reality’ windscreens, which superimpose instrumentation readings, local navigation guidance, speed limit warnings and hazard warnings in the driver’s line-ofsight. There is, in short, a rich body of work going on in the field of automotive glass innovation, embracing advanced glass formulations, coatings, advanced laminate materials, glass technology itself, and electronics. However, not all of that work will make it out of the laboratory, and even less will move into mainstream automotive manufacturing.
Innovations for the volume market
Augmented reality windscreens, for example, aren’t slated for introduction into vehicle production for perhaps another decade, points out Davies. And then, most likely, only in expensive high-end vehicles, far from the automotive mainstream. More prosaically, he suggests, a compelling advance would be better scratch resistance: a 100,000-mile service life exposes vehicles to a lot of dust and debris, and scratch-resisting coatings themselves degrade over time. So which automotive glass innovations are gaining traction in the volume market mainstream? How do they work, and what are the underlying technologies? Talk to those close to the industry, and a fascinating picture emerges.
Comfort and, as a by-product, fuel economy are big drivers. The name of the game is to move away from simple heat and light energy-absorbing materials, to technologies that actually reflect heat and light back out into the environment. “Energy-absorbing glass is simply glass that is tinted so as to be as dark and absorptive as possible while meeting applicable safety standards, which typically call for 70% visibility,” says Rob Vandal, vice-president of product engineering and development at Guardian Glass. “But where does the energy go? Especially in a vehicle that is parked, it’s simply entering the vehicle in a different form, as convective energy, versus radiation energy.”
Laminating and coating technology
A better solution, he explains, lies in exploiting laminate and coating technology in order to create reflective capabilities. Guardian’s Solar Management Glass product range, which employs simple tinting, delivers a Total Solar Transmission (TST) coefficient of around 57%, versus untinted glass’s coefficient of 62-65%. Guardian’s SilverGuard product range, though, is actively reflective – and typically, says Vandal, it delivers a TST coefficient of 4-50%, depending on the coating employed.
“The idea is to be very efficient at letting through visible light, but reflect over 90% of the energy that’s outside that visible light spectrum,” he explains. “Over the life of the vehicle, the impact on air conditioning use – and therefore fuel consumption – can be highly significant.”
Typical of the energy falling outside that visible spectrum is ultra-violet (UV) light. In December, Japan’s Asahi Glass (AGC) announced the first shipments of its ‘UV Verre Premium Cool on’ glass, claimed as a world first in tempered glass for automotive front door windows that filters out about 99% of UV rays and also eliminates infrared rays that cause excess heating of drivers’ arms.
Installed in Toyota’s special edition Vitz model released in December, the glass is an evolution of AGC’s ‘UV Verre Premium’ glass, which is now reaching mainstream automotive markets. Now adopted by Honda, the UV-blocking glass has been installed in selected models of the Honda Fit compact car – the Honda Fit She’s, HYBRID She’s and HYBRID XH Selection.
Underlying the product is the integration of AGC’s technologies in glass materials, coatings and chemicals, in order to create a glass that simultaneously filters out UV and infrared rays, while being scratch-resistant enough for service in frequently opened and closed door windows.
For its part, Saint-Gobain Sekurit has recently developed a new windscreen technology called SGS CoolCoat, claimed to deliver twice the performance of comparable heat-reflecting products. Based on a multi-layer coating on the inner glass layer of the glass ‘sandwich’, the main constituent of the invisible coating is thin layers of metallic silver which act as a mirror, reflecting the heat of the sun directly back outside the vehicle.
Heat management glazing packages – where the SGS CoolCoat windshield is combined with dark-tinted glazing – improve performance still further. A recent study by Saint- Gobain Sekurit showed how such an optimised solar control glazing package could boost fuel economy even further; by using a heat management glazing package comprising SGS CoolCoat and dark-tinted glazing, a saving of 30% in air conditioning usage was possible, compared to standard green-tinted glazing.
And it’s not just the elimination of heat that is driving innovation; noise reduction, too, is on the agenda, impelled by the growing prevalence of handsfree mobile telephones, and the increased use of vehicles as mobile workplaces.
Saint-Gobain Sekurit acoustic glass is to be found in the latest Mercedes B-Class, for instance, incorporating a special sound absorbing and noise dampening intermediate layer comprised of acoustic PVB foil. Better still, the product is slightly thinner than conventional 5mm glass, delivering at 4.5mm the same performance at a weight saving of 1.5kg per vehicle, while reducing the noise of passing vehicles and wind ‘roar’ by 3-5dB.
However, impressive though these advances are, adoption is uneven. While every single one of the major automotive glass manufacturers – of which there are but a handful around the world – can point to innovations in solar heat management, noise reduction, scratch resistance and so on, the reality on the road is more prosaic. While there’s a rich innovative seam out there, take-up is still driven by perceptions of cost, passenger comfort, durability and inherent value-formoney – upon which even simple decisions such as the move from absorptive glass to reflective glass, can flounder. Take solar management, for instance. In Europe, notes Guardian’s Vandal, energy reflective glass has made much greater inroads than in North America. Engine sizes are generally smaller, he explains, fuel costs are high, and air conditioning is less pervasive. Demand for reflective glass in North America, by contrast, fluctuates with gasoline prices, and has also suffered from a tendency for auto-makers to trim the range of options that they offer. Only now is the base demand rising, fuelled by competition from more highly-loaded Asian imports. “The American consumer hasn’t been educated in understanding the benefits and increased comfort of reflective glass,” rues Vandal. “And most likely, they won’t appreciate the difference until they actually change cars to one that does have reflective glass.”