Smart Systems

Fraunhofer FEP: Innovative pilot line for vacuum coating and thermal post-treatment of flexible ultra-thin glass

October 16, 2024. Flexible ultra-thin glass is an innovative material that combines the chemical resistance and scratch resistance of glass with the flexibility and weight reduction of plastics. This is primarily due to the low thickness of ≤100 µm. The processing of ultra-thin glass therefore requires dedicated handling to prevent glass breakage during production. Until now, this has been a major obstacle to the introduction of this innovative material into new applications. Within the Glass4Flex and CUSTOM projects funded by the Federal Ministry of Education and Research (BMBF) and the Federal Ministry of Economics and Climate Protection (BMWK), the project partners jointly developed a unique process chain for the in-line coating of ultra-thin glass at the Fraunhofer Institute for Electron Beam and Plasma Technology FEP and evaluated suitable characterization methods for the surface and edge strength of the thin glass to further optimize the properties of the material by flash lamp tempering.

Share this Post
Optical edge filter made of 20 sputtered layers on flexible thin glass, coated in a flat holder, curved frame design. Photo: Fraunhofer FEP

Contact info

Silicon Saxony

Marketing, Kommunikation und Öffentlichkeitsarbeit

Manfred-von-Ardenne-Ring 20 F

Telefon: +49 351 8925 886

Fax: +49 351 8925 889

redaktion@silicon-saxony.de

Contact person:

Ultra-thin glass with a thickness of 100 micrometres or less offers great potential for modern high-tech applications. Despite its superior properties, such as a smooth surface, high transparency and excellent barrier properties compared to polymer films, the material has not yet established itself on the mass market beyond foldable displays. A key obstacle is its tendency to brittle fracture, which is typical of glass and requires adjustments along the entire process chain. Such a process chain is now available at the Fraunhofer FEP in Dresden as a development and technology platform for feasibility studies up to pilot scale for innovative issues from cleaning to scaled in-line sputter coating, from handling and transfer to thermal post-treatment of thin glass.

To demonstrate the functionality of the process chain, two coating systems were produced on large-format thin glass at the Fraunhofer FEP – both on 100 µm “thick” thin glass with an area of 400 × 400 mm2 and on 700 µm thick thin glass with an area of 600 × 1200 mm2: an anti-reflective coating system consisting of 9 layers of zirconium oxide and silicon oxide (ZrO2/SiO2) and a transparent conductive indium tin oxide (ITO) layer as an example of an electrode application.

In addition to the suitable process parameters of the in-line sputtering processes, the homogeneous adjustment of the layer properties over the entire surface without edge shading is achieved primarily through the innovative integration of a flat support for the thin glass using moving electrostatic chuck systems from Glass4Flex partner ProTec Carrier Systems GmbH (see Fig. 3). For both application examples, it is essential to minimize the mechanical layer stresses during the sputtering process. For ITO coating realized at room temperature, it is also necessary to increase the conductivity and transparency of the layers through thermal post-treatment. Flash lamp annealing (FLA) using a xenon flash lamp at energy densities of up to 50 J/cm2 with a pulse duration in the millisecond range is an energy- and cost-efficient method compared to conventional furnace annealing.

Strength testing of ultra-thin glass as the key to success

A decisive factor in all these process steps is the strength of the glass, which is influenced by each processing step – from cutting to plasma pre-treatment to improve layer adhesion, coating or thermal post-treatment.

This is why strength testing of flexible thin glass is of particular importance. There are currently no standardized testing facilities and methods for thin glass, and standardized methods, for example from the architectural glass sector or optical applications, cannot be used or can only be used to a very limited extent due to the inherent flexibility.

In the course of the project, several mechanical testing methods were therefore adapted and further developed at Fraunhofer FEP in order to characterize the surface or edge strength and fatigue properties of thin glass, for example. Among other things, a YUASA bending test device adapted for thin glass from the company Bayflex Solutions from the portfolio of the CUSTOM project mentioned above was used for this purpose.

Application areas and future developments

Dr. Kerstin Täschner, project manager at Fraunhofer FEP, gives an outlook on the researchers’ next steps: “Interesting approaches for future applications of both the innovative thin glass material and the plasma coating and post-treatment processes on these flexible glasses pursue the goal of ensuring high edge and surface strength throughout all process steps, for example. Our research also focuses on production processes that increase strength in the future. This can be achieved, for example, through suitable process control in the coating and FLA post-treatment, but also by means of suitable FLA treatment approaches to increase the surface strength of the glass itself. We have already achieved a very promising effect of flash lamp tempering for 3 mm thick soda-lime glass.”

Future research projects will now investigate the effect of tempering on different types of glass and lower glass thicknesses, as established tempering processes, such as chemical ion exchange or thermal, do not achieve the desired effect, especially in the area of the thinnest thicknesses.

The Fraunhofer FEP is therefore actively working on the further development of these technologies. This expertise and the thin glass process chain are available to industrial partners as a technology and development platform. The spectrum ranges from initial feasibility studies to large-scale developments or pilot-scale sampling.

– – – – – –

Further links

👉 www.ikts.fraunhofer.de

Photo: Fraunhofer FEP

You may be interested in the following

Contact info

Silicon Saxony

Marketing, Kommunikation und Öffentlichkeitsarbeit

Manfred-von-Ardenne-Ring 20 F

Telefon: +49 351 8925 886

Fax: +49 351 8925 889

redaktion@silicon-saxony.de

Contact person: