It is hard to believe that less than a century ago, windshields were offered as optional equipment.  In 1909, Henry Ford offered his Model T with a windshield. Today, glazing continues to play an important part in vehicle design, providing a combination of aesthetic, functional and structural properties.  As a result, automakers are increasingly looking for their glazing suppliers to play a key role in the vehicle development process.  Matthew Beecham reports.


Panoramic roof systems

As glazing plays an increasing role in the overall design of a vehicle, automakers are looking for ways to use glass on other areas of the body. This has led to increased research into how sunroofs can be used more effectively as a design feature. The sunroof has subsequently emerged as a key styling feature and can in some cases replace the majority of the roof panel.  For example, a Peugeot 304 produced in 1969 carried a total of 2.24m-sq. The Peugeot 305 (produced in 1977) featured some 2.82m² of glass, while a Peugeot 306 (produced in 1993) carried 2.96 m² and the Peugeot 307 currently being marketed carries 3.3 m² of glass. Adding a panoramic roof on the latest generation Peugeot 307 SW results in a total glazed surface area of 5.34m-sq. 

A spokesman for PSA Peugeot Citroën told us: "The trend in automotive design is still toward complex, large area glass shapes and lower installation angles. The challenging work is to get good optical properties of the windshield, such as light transmittance, secondary image angle separation and distortion with respect to design demands and technical realisation. Today's optical requirements on the market are much restrictive than the regulations."

Consumer market research shows that 62% of buyers in the sports car segment are interested in having a sunroof or moonroof on their next vehicle.  In fact, just-auto estimates that production of large sunroofs has increased nearly 200% in North America between 2003 and 2006.  This trend is being driven in part by consumers' daily commute time.  The number of consumers with commutes of more than 60 minutes increased almost 50% between 1990 and 2000, according to the US Census Bureau.  With this in mind, this year, Ford will become the world's first automaker to feature a panoramic glass roof using Sungate infrared reflective (IRR) glass.  The technology will be fitted on the roof of the Ford Mustang GT and V-6 from this summer. The fixed glass roof rejects more than 95% of the sun's infrared energy while allowing more than twice the visible light of a conventional glass roof.  Rejecting the infrared energy keeps the car interior cooler and contributes to fuel savings when the air conditioner is running.

"The panoramic roof of Sungate glass provides the equivalent of 50 plus SPF ultraviolet [UV] protection, rejecting more than 99% of UV energy," said Mukesh Rustagi, PPG Industries' global product market manager.  "It's basically the sun without the burn. You couldn't buy a sunscreen lotion this good." 

According to Rustagi, the Sungate IRR glass technology reduces the initial workload on a vehicle's air conditioning system, which represents the biggest use of power for climate control in a vehicle.  "Because the air conditioner doesn't have to work as hard, fuel efficiency increases, and emissions are reduced," he said. The Mustang fixed-roof glass uses the same technology PPG features in its Sungate glass windshield.  Rustagi said PPG believes the use of Sungate glass will help automakers meet the tougher emissions and fuel economy requirements of the US Environmental Protection Agency's revised Supplemental Federal Test Procedure without compromising vehicle affordability, safety or performance.  According to Rustagi, PPG's panoramic glass application in the Mustang also uses the company's acoustic glass, as found in the SoundMaster windshield by PPG. The Mustang glass roof enables noise reduction of greater than eight decibels over standard tempered glass roofs at certain frequencies relevant to human hearing. 

Vehicle models unveiled at recent motor shows appear to adopt different philosophies in terms of automotive design.  For instance, we are seeing both high shoulder line and low shoulder line.  But these two tendencies have one thing in common: their openness to the outside world, which is highlighted thanks to the transparency of their roofs.  "Openness to the outside, well being and atmospheric comfort are today adopted by many OEMs as key functions, very often requested by the final user," said Bruno Pouillart, operational marketing manager for Saint-Gobain Sekurit.  "You can recognise that automotive glazing gets more and more important for the car manufacturers concerning the future design. Additionally many car manufacturers go in the direction of openness through glazing. Nowadays big surfaces can be seen on many cars because glazing and light are key elements to generate a positive atmosphere inside the car. In addition it supports a notion of innovation. Thanks to the various existing types of sunroofs and canopies today available on the market everyone can take profit of more light and nice atmosphere inside the car."

Larger windshields

Higher and wider windshields have led to the quantity of glass used in vehicle manufacture to gradually increase. The trends in MPVs, for instance, have seen bulky A-pillars become obtrusive for forward vision.  Consequently, some car designers are focusing more and more on windshields that wrap around at the sides pushing the A-pillar back towards the front door.  This style of windshield is known as panoramic.   

"[Panoramic windshields] are now a feature of virtually every concept car," said Derek Buckmaster, automotive marketing director, Exterior Body & Glazing, SABIC Innovative Plastics.  "There are a number of challenges there, of course.  The vehicle occupants are very exposed so you need to have good infrared and energy protection.  The structural elements present a challenge, which needs to be met, too.  Overall, the consumer interest in panoramic roofs has taken off at a faster rate than many of the OEMs originally expected. So I think we shall see more of that happening across Europe."

Windshields that extend further in height and curve into the roofline are also becoming more evident.  These are known as Cielo windshields. These are starting to appear, albeit in limited numbers.  For example, the new Opel Astra GTC with a panoramic windshield option was launched in Europe in 2005. The windshield offers the driver and front seat passenger an almost unlimited field of vision, similar to the view from an aeroplane's cockpit. The 1.78-m² arched panorama windshield extends seamlessly from the bonnet up over the front seats to the B-pillar, with no crossbeam restricting the view.  The screen is made of 6mm laminated safety glass and is used in conjunction with additional body and roof strengthening. 

"From the concept car point of view, we are seeing a number of designers using Ceilo windshields," said Michel van Russelt, market development director of Solutia Inc.  "In terms of occupant comfort, however, it requires special considerations in terms of heat and solar management."  

Lorna Payne, automotive market development manager of Solutia added: "That means there is a new opportunity for PVB manufacturers to play a role in solar control and anti-glare."

 "We are working on this area to develop some technical solutions," added van Russelt:  "But there are certain limitations.  For instance, a windshield must maintain 75% light transmission in the vision zone. So in terms of using solar absorbing PVB in the area where the windshield meets the roof, we are limited to the amount of absorbing particles we can actually place in that zone.  We do, however, have some interesting new technical developments underway but it is still too soon to talk about it. I would say that is 1 - 2 years away. We really want to be part of that wave of new technology since a lot of vehicle designers are thinking about this kind of glazing approach for the future. I would not be surprised to see these types of windshields going all the way up to the middle of the roof and then next to that you would have a glass panel to finish the roof of the car."

Acoustic comfort

Noise reduction inside cars and consequently, improvement of acoustic control is becoming one of the main objectives of carmakers.  Since the vehicle's glazed surface is continuously increasing, automotive glazing has become a very significant path for noise penetration inside the car. The use of acoustic windshields is gradually increasing.  The use of acoustic windshields allows carmakers to lighten their cars by using thinner glazing without sacrificing acoustic comfort.  This glazed sandwich offers three main benefits: increased comfort, security and safety. 

Laminated glass has solar and acoustic benefits and also helps protect against rollover and side impact injury while weighing less than standard glass of a similar thickness.

"We are seeing an increase in North America for laminated side glazing on certain vehicles provided by a variety of suppliers," said Rob Vandal, director of advanced product development, Guardian Automotive Products.  "At an industry level, there is a gradual increase in product fitment.  The North American trend has been that some high-end vehicles are getting it for security and acoustical benefits but the latest high volume adoptions have been in mid range vehicles for acoustic benefit. As soon as you laminate side glazing then you obtain an acoustic benefit, especially in the frequencies at which the human ear is sensitive, i.e. 3,000 - 5,000 hertz range.   But then if you add to that standard laminate an acoustic interlayer material then you simply improve the gain.  Realistically the gain going from a tempered to standard laminated side glass is a much bigger step than the additional gain of upgrading from laminated standard to laminated acoustic.  Yet there are some vehicles that have it."

Chuck Butler, marketing manager for DuPont Automotive agrees that side laminated glass continues to gain a whole lot of interest.  He told us:  "The primary focus these days by the OEMs is on emphasizing the acoustic and security benefits. Separating two panes of glass with a soft interlayer greatly reduces the amount of sound that transmits through the glass.  So there continues to be more and more vehicles that come out every year fitted with laminated sidelites - whether it is in the front row or both front and second. Laminated side glass also effectively blocks well over 90% of all UV rays. That is equivalent to an SPF of over 50.  Other benefits include occupant ejection mitigation in the event of a crash. Different interlayers offer different levels of ejection mitigation as well."

"We continue to see more and more call for laminated side glazing," added Pete Dishart, PPG global product manager.  "Although it started off as a luxury type of product, we are seeing automaker's such as Buick using laminated side glass as standard equipment on essentially all models.  We have also seen it as optional equipment on other mid-range car models.  For example, the Car of the Year at the [2008] Detroit auto show was a US$20,000 Chevy Malibu, a high volume vehicle fitted with acoustic laminated front door glass. The Detroit show also featured the Hyundai Genesis sedan which had laminated glass on all doors. That sedan will be available in the US in 2009."

For its part, PPG Industries' so-called Enhanced Technology Glass (ETG) is manufactured through collaboration between PPG and Saflex, a unit of Solutia Inc.  It is being applied on General Motors' 2008 model year full-size passenger vans.  "All 12- and 15-passenger vans have ETG to help protect passengers during a crash," said Steve Matsil, vehicle chief engineer, GM medium duty commercial truck and full-size vans.  "This specialty glass is located in the rearmost side window positions next to the fourth- and fifth-row passengers.  The glass is designed to help mitigate the risk of ejection for passengers seated next to the ETG windows." The use of ETG by GM in its full-size passenger vans marks the first ever use of this glazing technology in a vehicle. PPG Industries points out that ETG is an advanced glazing system that is really an evolution of its so-called Safe and Sound laminated glass, a product currently in use on other GM vehicles for reducing cabin noise.  Instead of using standard PVB, ET incorporates the Saflex K series interlayer -- a tough and resilient composite PVB structure designed especially for penetration resistance - laminated under heat and pressure between two sheets of PPG Industries' glass.  PPG Industries claims that this creates a glazing system that is stronger and more resistant to tearing and penetration than standard laminated glazing. "The 2008 Chevrolet Express and GMC Savana full-size passenger vans now offer the most comprehensive standard safety package ever in a GM full-size van," added Matsil.

It is clear that glazing continues to play an important part in vehicle design, providing a combination of aesthetic, functional and structural properties.  The need for improved passenger comfort, increased functionality and lower vehicle manufacturer assembly costs means that glazing systems with infra-red and ultra-violet inhibiting properties, integrated antennas, de-misting and de-icing capabilities and ease of fitting are increasingly required by the OEMs. It's a window of opportunity for the auto glass industry.

See also: Global market review of automotive glazing systems - forecasts to 2014