Five years ago, the sonorous paper loudspeakers from the Institute of Print and Media Technology at Chemnitz University of Technology were still produced in a semi-automatic single-sheet production process. At that time, the researchers had developed the "T-Book", a large-format illustrated book equipped with printed electronics. If you turn a page, it begins to sound through a loudspeaker invisibly located inside the sheet of paper. Normal paper or foils were printed with two layers of a conductive organic polymer as electrodes. In between, a piezoelectric layer was added as an active element, which causes the paper or foil to vibrate. The sound is produced by the displacement of air. The two sides of the loudspeaker paper can be printed in colour. Since this was only possible in single sheets in limited formats, the efficiency of this relatively slow manufacturing process is very low. Therefore, researchers at the Institute of Print and Media Technology have been looking for a new way - towards cost-effective mass production.
The goal of their latest project, "Roll Printed Speaker Paper" (T-Paper for short), was therefore to convert sheet production into roll production. Researchers from the fields of print media technology, chemistry, physics, acoustics, electrical engineering and economics developed a continuous, highly productive and safe roll production of loudspeaker webs. They not only used the roll-to-roll (R2R) printing process, but also developed inline technologies for other process steps, such as the lamination of functional layers. "In this way, electronics can be embedded in the paper - invisibly and protected," says Prof. Dr. Arved C. Hübler, head of the corresponding technology department at TU Chemnitz. In addition, inline polarisation of the piezoelectric polymer layers has been achieved for the first time and complete inline process monitoring of the printed functional layers is possible.