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Glass off the roll – Thin glass technology on display at Glasstec 2018

Thin glass – as thin as a razor blade or a human hair – has new applications in protecting smartphone touchscreens, sensitive filters and sensors. Yet despite its extreme thinness, recent advances have rendered it also highly resilient and scratch-proof. The flexibility and bending properties of the new thin-glass products may permit totally new applications in architecture, mobility and other industries.

Thin glass is opening up new markets and turning visions into reality. How this works can be seen at Glasstec 2018 in Düsseldorf.

Just as smartphones, tablets and e-book readers have changed the way we communicate and convey knowledge, scratch-proof touchscreens have produced totally new qualities in the manufacturing of glass, thus enhancing the performance of this material which has accompanied the history of mankind’s development since the first advanced civilizations. Ultra-thin protective glass seems more like film than glass and is so bendable and flexible it can even be rolled up and transported to customers on rolls. Special manufacturing processes are now available, allowing for the production of ultra-thin glass films which – at 0.025 millimeters thick – are even thinner than a human hair or razor blade.

Thin glass – manufacturing methods and definition
The starting material for production is molten glass which passes through rollers and is drawn upward or downward from a tank in what is known as an up-draw or down-draw process. It is then left to cool down on the production line as a film with the required thickness, ranging from 25 micrometers to 10 millimeters. Alongside these two methods – which, incidentally, are older than float glass manufacturing – thin glass can also be produced with different specifications using overflow or micro-floating processes. Whichever method a company chooses, the decisive element for the properties of thin glass is the formula of the molten glass, which differs from one manufacturer to another and is a well-guarded trade secret.

Thin glass is in demand for a wide range of products in numerous industries and can be classified quite differently, depending on its thickness. In construction and architecture, glass is considered to be thin if it is below three millimeters, with virtually no reasonable or practicable use for thicknesses below one millimeter. The needs are quite different elsewhere. In media technology, for instance, two-millimeter glass would be regarded as rather thick. This industry commonly measures thickness in micrometers and ultra-thin glass down to 20 micrometers tends to be treated as film and shipped on rolls. In the construction industry, thin glass can therefore be produced under a conventional floating process where minimal thicknesses are commonly around one millimeter.

The benefits of thin glass are its material and structural qualities on the one hand and its low weight on the other. There are potentials for this technology in combination with other glasses, for instance in insulating glass units. The stability and resistance of thin glass can be further enhanced through chemical tempering – something which is particularly in demand for displays and protective covers on smartphones. Other applications are protective covers for microscopic instruments and near-infrared filters for smartphone cameras.

Thin glass in construction and architecture
The construction industry, too, uses thin glasses to cover a wide range of applications where polymer solutions have their limits (e.g. the coating on solar panels). Compared with a plastic film, glass is far more heat-resistant, keeps its shape, is gas-tight and has outstanding visual qualities.

Thin glass is being used more and more for the middle pane in triple glazing, where it allows a clear reduction of thickness and weight. One proposed pane structure comprises an outer float glass pane (four millimeters), a semi-tempered middle pane (two millimeters) and another float glass pane on the inside (three millimeters). Compared with conventional glazing, this combination reduces the weight from 30 to 22.5 kilograms per square meter. The benefits of light, thin glazing are particularly noticeable in refurbishment projects.

In architecture, thin glasses not only reduce weight but also excel with their combination of breakage resistance and high flexibility, allowing for more design freedom. They permit new and variable options in shape and design, as it is possible to add specially treated coats to thin glass through grinding or screen printing. However, such applications are still more a matter of vision than everyday use. Other forward-looking applications include integrated functional coats such as OPV (organic photovoltaics), where energy is harvested via windows and switchable PDLC (polymer dispersed liquid crystal) coatings. This technology permits the creation of cloudy, opaque viewing guards, which only become transparent under an electric current. One specialist in this type of technology is the Austrian company LiSEC whose vacuum coating process with diffusion-proof edge seals also protects functional coats from humidity and environmental impact. At Glasstec 2018, LiSEC will present, among other things, suitable machines for the treatment of thin glass.

Thanks to thin-glass technology, curved glasses may well become increasingly established in architecture. Tempered thin glass can be bent into the desired shape on site either through cold bending or installation bending and can then be used as single glass or as a coat. It is an inexpensive alternative to hot bending at the factory. Furthermore, cold-bent glass has excellent visual qualities, due to fewer distortions.

Thin glass in the micrometer range makes glass particularly flexible without compromising on stability and hardness. One company that specializes in the development and production of ultra-thin glass is Schott, which uses its own down-draw technology. Its project AS 87 Eco has led to what is currently the world’s thinnest glass, at only 25 micrometers, and is now mass-produced for sensitive applications (e.g. fingerprints) and optical components (camera filters) in smartphones, where it offers reliable protection. The market for this type of glass is enormous.

Furthermore, flexible thin glass is also opening up new innovative options in virtual, mixed and augmented reality (the computer-aided enhancement of our perception of reality). One vision for tomorrow’s electronics is to achieve a good level of bendability without compromising on the outstanding visual qualities, clarity and valuable tactile properties of glass.