Flexible OLED Designed for Operating Rooms

As part of the joint LAOLA project (funding code : 03INT509AF), which was funded by the Federal Ministry of Education and Research of Germany (BMBF) and has now been completed, should develop applications for large area lighting with organic LEDs (OLED) on flexible substrates.

The project focused on ultra-thin glass, which has advantages over plastic as a substrate due to its excellent barrier properties.

At the Institute of Organic Electronics, Electron Beam and Plasma Technology FEP Fraunhofer OLEDs were applied to flexible glass using a “roll-roll” process. A surgical lantern designed using this process will be presented at LOPEC 2022, March 23-24, 2022, in Munich, at the joint stand of the Organic Electronics Project Coordinator Saxony eV (OES), № B0.308.

Homogeneous light without glare from organic large area LEDs (OLEDs) is perceived as pleasing and offers many benefits for product design. The recently completed LAOLA OLED project has been developed as a plane lighting for a wide range range applications on flexible substrates.

The project focuses on flexible ultra-thin glass, which has advantages over plastic as a substrate due to its excellent barrier properties. Some of the technologies have been explored as part of an internationalization project between Japan and Germany linked to LAOLA with partners in collaboration with the Japanese partner cluster YUFIC at Yamagata University. In particular, the creation of flexible ultra-thin glass as a substrate has been advanced here.

To consider suitable applications in addition to technological developments, WOLFRAM designers and engineers (WDI) have developed a specific application area for OLED on ultra-thin glass.

It has been implemented as a surgical light that combines large luminous OLED surfaces with LED spotlights in their design form. OLED elements are installed as wings and provide indirect lighting without glare, and LED floodlights provide direct lighting.

A number of other partners have collaborated to produce genuine OLED on ultra-thin glass. The beginning of this value chain is Nippon Electric Glass Co., Ltd. (NEG) as a manufacturer of ultra-thin glass rolls. At Yamagata University, a transparent conductive oxide (TCO) was applied to ultra-thin glass 300 millimeters wide for further processing as an anode material for OLED.

However, the resistance of the sheet of ~ 30 ohms per square meter is not enough for uniform illumination of the entire light area of ​​206 × max. 95 mm². To solve this problem, thin gain lines were printed. This was done on a roll-to-roll basis screen printing systems at Yamagata University in collaboration with SERIA Engineerinmg, Inc. (screen printing process from roll to roll) and Fujikura Kasei Co., Ltd. (manufacturer of printing paste).

“Ensuring the long-term stability of OLED devices and the hygienic surface of the luminaire is played key a role in choosing ultra-thin glass as a substrate, ”said Dr Jacqueline Hauptmann, a scientist at Fraunhofer FEP. easy to wind, cover and encapsulate pure ultra-thin glass 50 and 100 micrometers thick with a strip tension in the range of 30 – 50 newtons. The reconstruction of the plant was successfully carried out by FHR Anlagenbau GmbH.

The metal evaporator was re-equipped by the project partner CREAVAC-Creative Vakuumbeschichtung GmbH to apply thin layers of metal in the process of roll application of anode and cathode coatings. This allowed calcium and silver to evaporate simultaneously to obtain transparent layers 8 nanometers thick (calcium / silver ratio 1: 7) 290 millimeters wide with a change in layer thickness of 11%.

The necessary laser cutting and structuring processes for OLED separation and interconnection proved to be another challenge. Together with the project partner Heliatek GmbH, an alternative structuring method has been developed that has the potential for further structuring of already completed low-particle devices.

To do this, the anode, which is covered with printed passivation, is held by a laser through an ultra-thin glass. In addition, the use of thermally evaporated melamine was confirmed in the project and expanded with project partners Creaphys GmbH and Heliatek GmbH. Both technologies have enormous potential for use in new applications in flexible organic electronics.

The final OLED division can be successfully developed as part of a project with project partner 3D-Micromac AG. With the help of a laser equipped with Bessel1 optics, it was possible to demonstrate the so-called filamentation of ultrathin glass on both sides of the substrate and the encapsulation side and the subsequent mechanical separation of the adhesive. A cutting speed of 400 millimeters per second was achieved.

Various adhesive tapes for encapsulation in thin glass laminate, also with water trapping components, were tested from the tesa SE project partner, and cut glass and glass-laminate laminates were tested for mechanical strength.

Flexible stainless steel film from NIPPON STEEL Chemical & Material CO., LTD has been tested for encapsulation of opaque OLED devices. The 30 μm thin film can be very well processed by the roll-to-roll method and has the prospect of being a promising alternative to ultrathin glass encapsulation due to more favorable temperature control. The department of OLED glass, adhesive and stainless steel here is implemented by Mitsuboshi Diamond Industrial Co., Ltd. (MDI) 2.

In addition to coordinating projects, Organic Electronics Management GmbH has prepared market research for leading applications developed by WDI, as well as a manufacturing concept that paves the way for technology transfer by partners.

“Through the application of innovative manufacturing technologies to all partners, a promising OLED demonstrator has been developed that opens up new applications for flexible electronics,” said Dr. Jonas Jung, Project Manager at OES. “This remarkable result of the LAOLA project underscores the innovative strength of many years of German-Japanese cooperation.”

The results obtained in the three-year LAOLA project (2018 – 2021) can be directly transferred to other existing lines of rolled tapes. The successful separation of OLED modules from the composite glass and glass, which after processing was in a folded state, can also be easily transferred to the future.

1. White Paper: “Optimized laser cutting processes and system solutions for separating ultrathin glass for OLED lighting and displays”, Rene Libers.
2. “Roll-in-roll fabrication for OLED lighting using ultra-thin glass substrate and stainless steel foil encapsulation” – Tadahira Furukova, Jacqueline Hauptman et al., IDW’21, FLX5 / FMC6-1 2021

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