On a Roll: Thin Glass for Modern Applications
The resiliency, flexibility and bending properties of thin glass are enabling new applications in architecture, electronics, automotive, and other industries.
Thin glass is a reliable method to protect smartphone touchscreens, sensitive filters and sensors. Yet despite its extreme thinness, thin glass is also highly resilient and scratch-proof. In addition, due to its flexibility and bending properties, it enables new applications in architecture, mobility, and other industries.
Thin glass is opening up new markets and turning visions into reality. This technology can be seen at glasstec 2018 International Trade Fair for Glass Production, Processing and Products, which will be held October 23-26 at the fairgrounds in Düsseldorf, Germany.
Just as smartphones, tablets, and e-book readers have changed the way we communicate and convey knowledge, scratch-proof touchscreens have produced new qualities in the manufacturing of glass, thus enhancing the performance of this material that 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 that it can be rolled up and transported on rolls. Special manufacturing processes are now available, allowing for the production of ultra-thin glass films that—at 25 µm (0.025 mm)—are even thinner than a human hair or razor blade.
The starting material for production is molten glass that passes through rollers and is drawn upward or downward from a tank in what is known as an up-draw or down-draw process. The glass is then left to cool down on the production line as a film with the required thickness, ranging from 25 µm to 10 mm. 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 3 mm, with virtually no reasonable or practicable use for thicknesses below 1 mm. The needs are quite different elsewhere. In media technology, for instance, 2-mm glass would be regarded as rather thick. This industry commonly measures thickness in micrometers, and ultra-thin glass down to 20 µm 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 1 mm.
The benefits of thin glass include its material and constructional qualities, along with its low weight. The stability and resistance of thin glass can be further enhanced through chemical tempering, something that is particularly in demand for displays and protective covers on smartphones. Other applications include protective covers for microscopic instruments and near-infrared filters for smartphone cameras.
Construction and Architecture
The construction industry uses thin glasses to cover a wide range of applications where polymer solutions have their limits. 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 increasingly used for the middle pane in triple glazing, where it allows a clear reduction of thickness and weight. A pane structure comprises an outer float glass pane (4 mm in thickness), a semi-tempered middle pane (2 mm) and another float glass pane on the inside (3 mm). Compared with conventional glazing (4/12/4/12/4), this combination reduces the weight from 30 to 22.5 kg/m2. The benefits of light, thin glazing are particularly noticeable in refurbishment projects.
In architecture, thin glasses not only reduce weight, they also excel with their combination of breakage resistance and high flexibility to enable specific customizations. Moreover, they permit new and variable options in shape and design, as it is possible to add specially treated coats to thin glass (e.g., 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 organic photovoltaics (OPVs), where energy is harvested via windows, and switchable polymer-dispersed liquid crystal (PDLC) coatings. This technology permits the creation of cloudy, opaque viewing guards that only become transparent under an electric current. One specialist in this type of technology is the Austrian company LiSEC; its vacuum coating process with diffusion-proof edge seals also protects functional coats from humidity and environmental impact.
Thin glass technology could enable curved glasses to 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. In addition, cold-bent glass has excellent visual qualities due to fewer distortions.
Media Technology and Automotive Engineering
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 AS 87 eco has led to what is reportedly the world’s thinnest glass (25 µm), which is now mass-produced for sensitive applications such as fingerprint sensors and optical components (e.g., camera filters) in smartphones, where it offers reliable protection.
The market for this type of glass is enormous. Demand is steadily increasing for fingerprint sensors, as well as for special solutions to protect such sensitive components. The number of units shipped to customers in 2014 was 316 million; this figure rose to nearly 500 million in 2015, and the forecast for 2020 is currently as high as 1.6 billion units. Fire-polished protective glass is amazingly hard and is therefore also used for smartphone displays. In addition, it is as thin as a razor blade, which makes the precision of the manufacturing process particularly remarkable. With a thickness tolerance of only 10 µm or less, it promises a high level of reliable safety and quality.
Flexible thin glass is also opening up new innovative options in virtual, mixed and augmented reality (i.e., 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.
Thin glass is also becoming more desirable in the automotive industry for the interior, freely shaped windscreens and the cockpit. Here, too, digitization has long been a well-established feature. It is a domain where highly resistant, scratch-proof, ultra-thin glass below 250 µm can be used to its full advantage, particularly in convex and concave geometries. Glass does not age and is therefore superbly suited for the paneling of vehicle interiors.
In the past, such applications involved a risk of injury in an accident and were therefore unthinkable. However, thin glass has now achieved such a high level of stability, almost unlimited moldability, and superior optical qualities that it has opened up new paths in automotive engineering and has become a truly viable alternative to plastic. Its optical qualities and homogeneity are far better, and its chemical and thermal resistance are so high that it can easily withstand humidity, UV radiation, and high temperatures.
In sheet glass, the main focus at glasstec 2018 will be on interactive glass, while in container glass it will be on energy-efficient and emission-reducing technology for glass production. The most important target group for exhibitors is the glass industry, followed by mechanical engineering, architecture, the construction industry, the German trade sector, and increasingly the trade sectors of other countries.
Glass technology live will be held in Hall 11. Four glass cubes will feature innovative solutions from the areas of interactive façades/display glasses, energy and performance, construction glasses (solid and thin glasses), and forward-looking technologies. As the glass conference venue, Hall 10 will feature thematic combinations of theory and practice in form of conferences.
For more information, visit www.glasstec-online.com.