But the glass substrate makes LCD displays rigid and fragile, limiting their use. Now display manufacturers are working to develop a new generation of robust, flexible displays that can be curved to fit the shape of a product or even rolled up like a magazine. The question is, which of the technologies under development is the best?
“Research to define the route forward for flexible displays is too great a job for one particular company, institute or university,” says Dr Eliav Haskal of Philips Research who is coordinating the EU-funded FlexiDis project. “When we started the project nobody knew exactly what to do, there were many different solutions.”
Big industrial names such as Nokia, Thales and Philips, as well as universities, research centres and many small and medium-sized businesses have pooled their skills and expertise to thoroughly test a large number of materials and techniques.
Alternatives to glass
Displays have two principal assemblies: a ‘backplane’ with the electronics that drive the display, and a ‘frontplane’ containing the actual display elements.
Backplanes are conventionally made of glass on which is deposited the grid of thin-film transistors (TFTs), which control the state of each pixel in the display. To create a flexible display the FlexiDis researchers needed to find an alternative to glass.
One possibility was thin metal, which is particularly attractive for a promising new kind of light-emitting element called an OLED (organic light-emitting diode). Unlike an LCD an OLED emits its own light rather than filtering light from a background source and so has the potential to create full-colour displays using much less power than LCDs.
OLEDs can also switch on and off much faster than an LCD making them suitable for video displays such as TV sets.
“The initial guess was to work with metal substrates because metal is a very good barrier to water and oxygen both of which are known to degrade the lifetime of OLEDs,” says Dr Haskal.
Metal also has the advantage of being stiff enough to be handled in factories designed to manufacture displays based on glass, a very important economic consideration.
It turned out that constructing a metal-based backplane suitable for OLEDs was very difficult, so the partners also decided to investigate the possibility of constructing OLED displays on a plastic backplane.
“We had to introduce a method of making thin-film transistors on plastic in a process which can be run in a production facility,” says Dr Haskal. “Ultimately that was the biggest problem.”
Conventional transistors are typically made at temperatures around 280°C, which is too hot for most plastics. Rather than try to reduce the temperature of a standard process, the researchers decided to develop two alternatives.
One method used a heat resistant plastic called polyimide at 280°C. The other alternative was to use organic TFTs, which can be deposited at much lower temperatures.
Electronics on plastic
The FlexiDis partners have now developed three new technologies for producing flexible plastic backplanes. The first, called EPLaR (electronics on plastic by laser release), uses polyimide spin-coated on to a glass plate. The TFTs are formed on the plastic in the usual way and the whole backplane assembly is then released from the glass by a laser process.
The other two technologies use organic TFTs deposited at 120-150°C, a temperature at which many more plastics can be used. In one process the TFTs are built up by ink-jet and in the other a spin-coating process is used.
These three technologies have found their first commercial applications with a monochromatic display that can show high-resolution images.
So-called ‘electrophoretic’ displays are the basis of what has been called ‘e-paper’, which reflects light just like normal paper and can hold an image without consuming any power. The glass-based version of this technology has been commercialised in the Sony Librié, the Amazon Kindle and the IRex Iliad.
Two European companies are launching e-readers based on the FlexiDis technologies. A factory in Taiwan has been licensed to mass produce flexible displays for the consumer market. Thales Avionics LCD are planning to industrialise flexible displays for the avionics sector.
Although the OLED technology is further from the market – FlexiDis partners demonstrated the first flexible OLED display in 2007 – it offers the best prospects for creating flexible displays that can support full colour and video.
In the longer term, the development of full colour displays could make possible the kind of moving newspaper pictures seen in movies such as the Harry Potter series and Minority Report.
“Everyone in this industry has watched Minority Report because of the ideas about working with newspapers which show constantly updating information in full colour and full video,” says Dr Haskal.FlexiDis received funding from the EU's Sixth Framework Programme for research.
Ahmed ElAmin | alfa
Ultra-precise chip-scale sensor detects unprecedentedly small changes at the nanoscale
18.01.2017 | The Hebrew University of Jerusalem
Data analysis optimizes cyber-physical systems in telecommunications and building automation
18.01.2017 | Fraunhofer-Institut für Algorithmen und Wissenschaftliches Rechnen SCAI
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences