LEDs integrated with roll-to-roll process to make light-emitting foils

Combining high-speed, self-assembling methods with a roll-to-roll approach, European researchers have developed a prototype modular-based process for producing flexible displays integrated with light-emitting diodes (LEDs).

Image of flexible LED display courtesy Design LED Products.

Dubbed the Light Rolls project, the R&D effort to develop a high-throughput production platform for the manufacture of light-emitting components brings together researchers from eight countries. Research partners include: Prodintec, Gijón, Spain; microTEC Gesellschaft für Mikrotechnologie mbH,  Duisburg, Germany; Norbert Schläfli Maschinen, Zofingen, Switzerland; Centro Ricerche FIAT S.C.p.A., Orbassano, Italy; Design LED Products Ltd., Livingston, United Kingdom; Xaar Jet AB, Järfällaweden; ACP-IT GmbH, Villach, Austria; Fraunhofer IPA, Stuttgart, Germany; and microelectronica S.A., Voluntari, Romania.

The Light-Rolls equipment platform will process a thin, transparent foil as a substrate layer in a roll-to-roll process. The platform is suitable to integrate microfabrication processes. The aim of the equipment concept to be developed is to realise micro-fabrication process chains in a high throughput production line. NSMZ will develop the equipment platform. To achieve the high standards for volume production, ACP will develop quality control and required control software systems. To use this kind of equipment platforms in further applications IPA and the Light-Rolls partners will develop a knowledge base for i) design for manufacturing and  ii) for configuration of production lines.

The platform, which is based on a patented process technology—RMPD®-rotation—that is said to generate 3-D polymer structures using a fast generative manufacturing process, will incorporate new new self-assembling chip methods and high-resolution, speed-conductive track generation and interconnection based on ink-jet and laser-printing technologies, according to the Light Rolls Web site.

"Nanoparticle dispersions used in fast conductive track printing technologies will allow the parallel generation of conductive lines," according to the microTEC Web site. "These processes comprise the founding elements of the Light-Rolls technology platform with a roll-to-roll philosophy."

A key element of the design is its modular approach, which is expected to pay dividends beyond the production of flexible LED displays.

"The manufacturing modules will be integrable [and] exchangeable with mechanical, fluidic and information technology interfaces to make it easy and cost-efficient to adjust the sequence of process steps to the product to be produced," microTec explained.

So far, the European research team has validated the integration of a 2x2 array of 0.25mm, blue GaN LED chips onto a flexible substrate using the RMPD®-mask process. The overall thickness of the component is 0.45mm.