Given the trend for larger sunroofs, glass makers are working on ways in which to meet heat absorption as well as privacy requirements. Matthew Beecham takes another look at some infrared reflective (IRR) trends in the automotive market.
The use of roof glazing is becoming an increasingly important development for the automotive glazing industry with certain automakers leading the market, notably BMW, Cadillac, Citroen, Ford and Peugeot. Novel panoramic glass roofs bring weight, noise, solar control and cost issues. Although toughened glass can meet most of these demands, it can limit the opportunities for adding value and functionality.
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Rob Vandal, Vice President Systems Innovation, Guardian Industries Corp sees automakers moving to laminated roof systems in order to help mitigate ejection concerns and improve security and safety. He told us: “This issue will continue to gain relevance as the FMVSS 226 rule indicated the next likely area of focus will be roof systems as they are the next likely path of ejection, especially as they become larger.”
Mukesh Rustagi, Pittsburgh Glass Works, LLC agrees that as car sunroofs are becoming larger, more and more OEMs are moving to laminated constructions for the roof glass. “The larger glazing requires higher level of performance which can only be obtained through the use of laminated constructions. For example, solar loading, UV exposure, security, noise etc. can all be improved with laminated glass over tempered glass. We expect to see a strong growth in the use of laminated roofs in North America.” Vandal adds: “We see growth in laminated roof systems and with that an associated growth in the use of IRR.”
Indeed, the use of IRR windshields has been shown to reduce cabin temperature and interior surface temperatures and the effect can be increased with IRR glazing applied to side and rear windows. Peter Buettrich, Business Manager, Advanced Materials – Interlayers, Eastman Chemical Company believes that there are several glass manufacturers that have coating-on-glass capabilities for automotive applications, mostly for windshields although some sidelite applications are available. “But generally speaking there is a very limited capability with regards to coating-on-glass for sidelite applications and that is why, in most cases, an interlayer reflective film is used.”
Over the past decade we have seen some significant improvements in the design and application of IRR glazings. Yet Rustagi believes that there is still a lot of room for improvement in the performance of the IR reflective. “We believe that the next generation of IR reflective products will improve the heat load performance, probably by as much as the current generation does over the standard tempered glass. So it could double the improvement over the next generation product. We also believe that there is further room for improvement with potentially switchable technologies.”
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By GlobalDataMeanwhile, metallic windshields are installed on many European and North American vehicles. Some argue that these windshields can potentially interfere with the radio frequencies used when operating remotely-controlled garage doors, portable sat-navs and electronic tolling devices. Manufacturers have, however, anticipated this and in nearly all cases metallic windshields feature a non-metallic (deletion) area that allows such devices to function without interference. In this regard, Giovanni Occhionorelli, Marketing Manager, AGC Automotive told us: “Although we have heard about this, we have not found it to be an issue since there are areas of the windshield without such coatings. There are also non-metallic radio wave transparent solutions available but they are lower in thermal performance and are not always so aesthetically accepted.” Vandal added: “CARB ran some tests a few years ago and found no appreciable effect on cell phones or navigation systems. That said, they did find a negligible delay in operation if the navigation system was placed directly behind the coating.”
While metallic windshields are common in the West, non-metallic interlayers are still in use. Pete Dishart, Pittsburgh Glass Works, LLC points out that IR absorbing interlayers are being used by some OEMs although they are not quite as effective on the heat reduction as IR reflective. “Typically, we find that a lot of the Japanese OEMs tend to use the IR absorbing technologies more, at least in Japan and in some of their cars that they export from Japan. For example, the Toyota Prius has IR absorbing technologies.”
Occhionorelli adds that the European market is still very much dominated by metallic IRR coatings. “IR absorbing in Asia dominates the market – for historical reasons – so it’s difficult for them to move to something else unless, say, led by a regulation.”
Meanwhile, Buettrich believes that car dealerships could help themselves by promoting IRR glazing, He told us: “Glazing itself has been for many years underestimated because dealers and drivers view it as little more than something that protects themselves from the elements. Yet glass is a very important part of the whole car, its structural integrity as well as integrating a number of value-added features. So while the importance of the glass now has been proved, the end user is not really aware of this.”
Finally, while IRR glazing is being increasingly applied to vehicles interest in acoustic glazing continues to gain momentum. Acoustic windshields are a soundproofing measure that differs from conventional laminated windshields in that it has a special layer of transparent sound-absorbing material between two layers of glass. It can reduce noise levels entering the cabin by up to six decibels. One of the factors contributing to consumer demand for quieter vehicles is the increasing use of telematics within the vehicle, including voice-activated technology and mobile phones. “Acoustic glazing is increasingly becoming a standard feature mainly in windshield applications,” concludes Buettrich. “Amongst certain upper-mid segment vehicles, we are even seeing it become standard for certain brands. For those vehicles that already have a laminated side glazing then the step for acoustic – and maybe adding an IR reflective feature – is not a big one. So the biggest step is going from tempered glass to laminated glass in side glazing.”
