Putting the coated side of the glass inside the sandwich protects it from impacts, abrasion, and corrosion. Laminated glass and solar control coatings are widely used in architectural glazing to make buildings more comfortable and energy efficient. Vehicle glazing uses the same basic technologies, but automotive applications involve some extra challenges, says Dr. Frank: “The automotive industry has strict standards relating to the optical properties of glass, especially in windshields and front windows. They are there to ensure the driver always has a clear view of the environment around them.” And then there’s weight. Extra mass requires extra energy to move it, and that is a particular problem for electric vehicles. To compensate for heavy batteries, carmakers are looking for ways to reduce weight elsewhere in the vehicle. One way to do that is with thinner glass. “Architectural glazing might use 4 millimeters (mm) to 6 mm glass sheets,” says Dr. Frank. “In automotive applications we see sheets as thin as 1 mm.”
Applying precise, complex coating stacks to large pieces of thin, flexible glass requires sophisticated manufacturing technology. That’s an area where Bühler has developed considerable expertise. Its specialist vacuum coating machines used in the automotive sector include numerous features designed for safe handling and effective quality control. They include closely spaced rollers to support the glass as it travels through the machine, and advanced process control. “After every stage in the process, we use in-line spectrometers to check the optical properties of the glass,” explains Dr. Frank. “Our machines use that data to continually adjust their operating parameters. If you ensure every layer in the stack is within specification, you know that the finished glass will perform as expected.”