Fraunhofer FEP: Optoelectronic systems on thin glass
The recently launched KODOS project (“Konfektionierter Dünnglas-Verbund für optoelektronische Systeme”, Thin Glass Composites for Optoelectronic Systems), funded by the German Federal Ministry of Education and Research, is designed to transform thin glass into finished products along the entire value chain. The companies EMDE development of light, Volkswagen and Deutsche Werkstätten Hellerau, which focus on application development, have joined forces with the technology suppliers tesa, VON ARDENNE, Flabeg, 4JET microtech, SURAGUS, and the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP (Dresden, Germany). The aim of the consortium is to be able to offer a complete modular system of functional materials, semi-finished products, tools, and technologies for the roll-to-roll production of optoelectronic systems on thin glass.
Sophisticated ultra-thin glasses have been on the market for some time now. They are thinner than display glass in mobile phones or laptops and can do a lot more. Due to their excellent properties, such as flexibility, very smooth surface or scratch resistance, they are also very suitable as functional surfaces in furniture or cars and as a substrate for optical systems.
In order to serve new applications cost-efficiently and in a market-oriented manner, a consortium of nine industrial and research partners has now formed, which is laying the basis for this in the public-funded project KODOS.
The automobile manufacturer Volkswagen will evaluate and qualify the use of thin glasses as functional decorative surfaces in cars. For this purpose, the laminated optical basic devices produced in the project are to be tested for their resilience and crash safety. They illustrate the properties of functional surfaces such as lighting, decorative symbols and touch functions.
The Deutsche Werkstätten Hellerau will seal wooden surfaces with the ultra-thin glass as high-tech material and integrate additional functions such as organic light emitting diodes (OLEDs) or sensor surfaces into furniture.
Thomas Emde of EMDE development of light and consortium leader summarises: "The aim of the project is to explore and develop economically relevant applications for thin glass. For example, OLED technology can be used as a display and control element in combination with touch functionality based on thin glass in architecture, furniture, household appliances and retail applications. The desired innovation is the combination of coating, structuring, contacting and lamination, as well as the development of a production-ready transition from the processed roll to the ready-to-install semi-finished product". EMDE development of light will create the requirements definitions for process optimisation in the areas of roll-to-roll and OLED production.
All the above-mentioned steps pose a major challenge, especially because of the special mechanical properties of thin glass. As a result of the project, the consortium will be able to offer a complete modular system of functional materials, semi-finished products, tools and technologies.
For lamination of basic elements, tesa provides encapsulation adhesive tapes for thin glass-based organic electronic devices. These must guarantee an improved service life in order to meet the high temperature requirements of the automotive industry. In addition, technologies are being researched for full-surface and partial direct coatings of thin glass foils with functional layers, such as hole-injection layers for OLEDs, electrical contacts, or decorative prints.
Flabeg develops important process steps that are necessary to be able to use 3D-formed thin glass laminates with touch function, decoration and including splinter protection properties as built-in parts in the vehicle interior. The project partner is researching in particular the hot moulding process and the lamination of uniaxially and biaxially bent thin glass.
Functional elements utilising thin glass to be developed in the project consortium are an important basis for later integration into applications during the course of the project. An essential process at the beginning of the value chain is the functionalisation of the glass surfaces by means of PVD coating.
In order to be able to produce economically, the processing of thin glass in roll-to-roll PVD coating systems is most reasonable. The aim of the plant manufacturer VON ARDENNE in the project is therefore to ensure stable, continuous process control with a high material yield and to develop quality parameters for evaluating the usability of the supplied thin glass rolls. In addition, the coating processes and components providing functionalities for subsequent processes (lamination, thermal deformation, laser cutting) are to be optimised.
In close cooperation with the scientists of the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, conceptual solutions for the technologically and economically meaningful interlocking of individual steps in the production chain (illustration of the process chain vacuum coating - encapsulation lamination - OLED contacting and separation) are formulated. The Fraunhofer FEP specialists are developing efficient coating technologies for electrodes and OLEDs. They will introduce new structuring tiers into roll-to-roll production. At this point, the work will dovetail with the know-how of the project partner SURAGUS in the field of process-integrated characterisation of essential electrical and optical properties. SURAGUS develops the measurement technology for the characterisation of the entire laminated OLED.
After successful production of the optical, thin glass-based devices, the next process step is the separation of the finished OLEDs from the roll. Currently, no reliable technologies exist at this point in the process chain. In order to use the enormous competitive advantage of roll-to-roll production, it is necessary to develop a separation technology that enables yielding OLEDs with high edge strength and service life.
An advantageous solution technology for this is laser separation, which is being researched by 4JET microtech. In principle, laser-cut glass edges can have strengths that meet the requirements of OLEDs. In particular, it is possible to produce practically any cutting contours and thus any OLED shapes. The specific challenges of glass-polymer laminates will be investigated within the framework of the joint project and competitive manufacturing technologies will be developed.
Within the next three years, the project consortium will work on the development of technologies that are practical and suitable for industrial use. In addition, the project includes the implementation of initial persuasive basic devices with the innovative material ultra-thin glass and preparation of technology demonstrators.
Caption: Thin glass is a versatile material with many possible applications in the organic and printed electronics industry (photo: Fraunhofer FEP)