Fraunhofer-Gesellschaft - Research News: Displays for the pants pocket

Research News 6 - 2002
Topic 6 Displays for the pants pocket

For further information:
Dr. Armin Wedel
Phone +49 3 31 / 5 68-19 10
Fax +49 3 31 / 5 68-39 10

Dr. Silvia Janietz
Phone +49 3 31 / 5 68-12 08

Fraunhofer-Institut für Angewandte Polymerforschung IAP
GeiselbergStrasse 69
14476 Golm, Germany

Link:
IAP: Polymer Light Emitting Diodes

Much to the disappointment of many users of computer and portable electronic information device, flexible screens still cannot be found in retail stores. The reasons are mainly of technical and chemical nature, as Dr. Armin Wedel from the Fraunhofer Institute for Applied Polymer Research IAP explains: ”Many developers of displays which you will simply roll up and stick in your pocket are using organic light emitting diodes or OLEDs.” When a voltage is applied to semiconducting plastics, they begin to emit light in different colors. Such special polymers have one thing in common: many double bonds and aromatic rings or - in chemical terms - conjugated pi-electron systems. This causes the inevitable drawback that the chemical bonds become susceptible to oxidation when electric current is applied. ”You can, of course, keep the atmospheric oxygen out with a glass cover, however this makes the display rigid,” as Wedel knows. But the Working Group for Polymers and Electronics is optimistic that in the future they will be able to design polymer displays with a durable protective coating based on a substrate of modified, flexible film made of polyethylene terephthalate (PET).
The prototypes are still comparatively small and rigid, however the initial focus is to demonstrate that the technology works. So far, 28-x-32-pixel monochrome monitors measuring 50 x 35 millimeters have been developed together with Optrex Europe GmbH. This is already considered a great success when Dr. Wedel takes into account that ”not many companies around the world are in a position to produce light-emitting polymers with the required level of purity and quality.” His colleague Dr. Silvia Janietz explains just a few details of the process: ”After our multi-stage and pretty challenging chemical synthesis, we have to ensure that extrinsic moieties such as ions are removed down to a very low concentration. Another task is to ensure that the polymer chains have an almost completely uniform chemical structure and do not exhibit any molecular defects. Only then are we able to obtain basic polymer materials that are capable of producing luminescent red, green or blue colors of an adequate brightness.”

At present, the IAP scientists still deposit their polymers on planar substrate by means of spin-coating. This process uniformly coats the rotating plates with polymer solutions. In future however, we should see optical and electronic circuits being manufactured at low cost using the same principle as that applied in ink jet printing.

© 2002
Fraunhofer-Gesellschaft


Research News 6 - 2002 Topic 6		Displays for the pants pocket

For further information: Dr. Armin Wedel Phone +49 3 31 / 5 68-19 10 Fax +49 3 31 / 5 68-39 10 Dr. Silvia Janietz Phone +49 3 31 / 5 68-12 08 Fraunhofer-Institut für Angewandte Polymerforschung IAP GeiselbergStrasse 69 14476 Golm, Germany Link: IAP: Polymer Light Emitting Diodes		Much to the disappointment of many users of computer and portable electronic information device, flexible screens still cannot be found in retail stores. The reasons are mainly of technical and chemical nature, as Dr. Armin Wedel from the Fraunhofer Institute for Applied Polymer Research IAP explains: ”Many developers of displays which you will simply roll up and stick in your pocket are using organic light emitting diodes or OLEDs.” When a voltage is applied to semiconducting plastics, they begin to emit light in different colors. Such special polymers have one thing in common: many double bonds and aromatic rings or - in chemical terms - conjugated pi-electron systems. This causes the inevitable drawback that the chemical bonds become susceptible to oxidation when electric current is applied. ”You can, of course, keep the atmospheric oxygen out with a glass cover, however this makes the display rigid,” as Wedel knows. But the Working Group for Polymers and Electronics is optimistic that in the future they will be able to design polymer displays with a durable protective coating based on a substrate of modified, flexible film made of polyethylene terephthalate (PET). The prototypes are still comparatively small and rigid, however the initial focus is to demonstrate that the technology works. So far, 28-x-32-pixel monochrome monitors measuring 50 x 35 millimeters have been developed together with Optrex Europe GmbH. This is already considered a great success when Dr. Wedel takes into account that ”not many companies around the world are in a position to produce light-emitting polymers with the required level of purity and quality.” His colleague Dr. Silvia Janietz explains just a few details of the process: ”After our multi-stage and pretty challenging chemical synthesis, we have to ensure that extrinsic moieties such as ions are removed down to a very low concentration. Another task is to ensure that the polymer chains have an almost completely uniform chemical structure and do not exhibit any molecular defects. Only then are we able to obtain basic polymer materials that are capable of producing luminescent red, green or blue colors of an adequate brightness.” At present, the IAP scientists still deposit their polymers on planar substrate by means of spin-coating. This process uniformly coats the rotating plates with polymer solutions. In future however, we should see optical and electronic circuits being manufactured at low cost using the same principle as that applied in ink jet printing.

		© 2002 Fraunhofer-Gesellschaft