Researchers develop cost-effective electronic display printing press

European researchers have created a cost-effective method for manufacturing electronic flexible display using a revolutionary printing method. Their work promises to revolutionise packaging, advertising and even clothing.

The EU-funded ROLLED project has developed a technique for manufacturing OLED devices at considerably lower cost than current methods.

Using the unique properties of OLEDs (organic light emitting diodes) mean displays using them can be put to a wide range of uses, from electronic paper to adaptive clothing – so long as production costs can be brought down.

Ultra-thin and energy efficient displays that use organic compounds to emit light have been stirring up excitement in the consumer electronics industry for several years. OLEDs are already being used commercially in some high-end flat-screen televisions, offering superior image quality, wider viewing angles and lighter power consumption than the current generation of liquid crystal display (LCD) and plasma flat-panel TVs.

“Lowering production costs is extremely important if OLED devices are to become more widespread, and particularly if they are not just going to be restricted to high-end applications,” explained Arto Maaninen, technical manager of the printed electronics department of the VTT Technical Research Centre in Finland.

Whereas the OLEDs now making their way into TV sets – such as Sony’s XE1 OLED display – announced in October last year – and some mobile devices, the ROLLED researchers print their OLEDs onto flexible protective films, a procedure known as roll-to-roll processing that allows thousands of devices to be rapidly and cost-effectively produced in a single 'print run'.

As part of their work, the researchers developed printable nano-particle indium tin oxide (ITO) coatings to form the anode, and they developed a new low-work function metal cathode, with the light-emitting organic layer sandwiched in between.

As an electric current passes from the anode to the cathode layer, the organic compound emits light that, depending on the application, can create a high-contrast TV image or a simple coloured sign. Each OLED sheet is just a fifth of a millimetre thick – equivalent to three or four sheets of paper.

“The biggest cost saving is on equipment. The equipment needed to print OLED displays is widely available, so the initial manufacturing costs are lower compared to other techniques. The material costs are about the same, but you can produce many more units in a much shorter period of time,” Maaninen said. “This brings down overall production costs three to five fold.”

The tiny amount of energy OLED devices need to operate mean they could be powered by a small watch battery, solar cells or even radio waves. “It might be possible for a store to use its shelves as an RFID antenna that would power the OLEDs in the product packaging,” claimed Maaninen.

“Our flexible OLED devices could be used in clothes – the biggest barrier would be making them robust enough to survive being worn and put through a washing machine,” said Maaninen.

Having developed the technical ability to produce flexible OLEDs roll to roll, the ROLLED project partners are now working to meet the needs and requirements of potential end applications. Their aim is to carry out the first market trials within the next two years.

For further consumer tech insider news, visit www.theiet.org/consumer

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