Sekisui Chemical Co. Ltd. announced at the beginning of July 2009 that it has developed an interlayer film for laminated glass for head-up displays. The SSF-W film features enhanced visibility, along …
Sekisui Chemical Co. Ltd. announced at the beginning of July 2009 that it has developed an interlayer film for laminated glass for head-up displays. The SSF-W film features enhanced visibility, along with sound and heat insulation properties. The SSF-W is part of the company“s S-LEC product series and was on show at the Automotive Engineering Exposition 2009, held at Pacifico Yokohama in Yokohama City, Japan, the second half of May. SSF-W is used as an interlayer film for automotive windshields equipped with head-up displays, usually offered as an option. “This is the world“s first interlayer film that realizes sound and heat insulation and visibility of head-up displays at the same time,” according to Sekisui. The new film, which is used by the Honda Insight, Toyota Prius and BMW “7-Series”, consists of three layers, with a sound insulation layer between two heat insulation layers, with thickness ratio of 3:2:3. The film is sandwiched by glass layers to make an automotive windshield, resulting in a completed windshield of five layers. Sekisui Chemical modified the thickness of the glass to enhance the visibility of the head-up display, with the vertical cross section of the front glass shaped like a “wedge”: thinnest at the bottom and thicker as it progresses to the top. The interlayer film is 0.8mm thick at the bottom and more than 1mm at the top. The driver sees characters and arrows from the fluorescent display tubes that light up from the area below the windshield as lights from two different channels. These lights are reflected by the glass on the cabin side (inner glass) while the light transmitted through the inner glass and the intermediate layers is reflected by the glass on the exterior side (outer glass). Thanks to the wedge-shaped windshield, the lights meet just in front of the driver, thus enabling him to see the numbers showing vehicle speed and the arrows indicating the direction of travel clearly. PVB (polyvinyl butyral) was used for the sound and heat insulation layers. An additive was used with the PVB in the sound insulation layer to soften it, thus enhancing the processing method and enabling it to absorb the vibration of the exterior glass, reduce the vibration transmitted to the inner glass and decrease the noise. This kind of sound insulation layer is especially effective for shielding sounds most audible to human ears, which are mid-frequency ranging from 1,000 to 4,000 Hz. The PVB material of the heat insulation layer, most effective for shielding the heat from 1.400 nm light contains almost homogeneously dispersed ultrafine nm-order indium particles, which absorb infrared light at the wavelength of about 800 to 1.800 nm and store heat. This heat is then released when the vehicle is driven thus cooling the outer glass.