Dec 2 2008
Sharper contrast, lower power consumption, slimmer display screens. Displays with organic light emitting diodes (OLED) in TV screen format are already on the market. Manufacturers are looking for ways to inexpensively produce these light sources using flexible substrates so that OLED will illuminate rooms in the future. Current trends and the latest developments in this field will be on display at the LOPE-C in Frankfurt, Germany from June 23-25, 2009. OLED displays are growing in size.
They have already been used in mobile phones or car radios for years and they just recently reached the television market. Meanwhile, prototypes of TV displays with 40-inch diagonal screens have already been introduced. These colorful light sources will, however, not be available in movie screen format for some time to come. Current concepts in large-area OLED applications have reached their limits as far as manufacturing and quality are concerned.
In the long run, printed OLEDs are expected to be the solution. They could be made of light-weight, flexible substrates that are printed with plastics, or so-called “polymers”. As polymers are soluble in various solvents and – depending upon their chemical composition – offer insulating, semi- conductive or conductive properties, they are suitable for cost-effective production of electronic components such as transistors, light-emittingdiodes or photo cells, through continuous printing processes
LCD Displays as Benchmark.
OLED displays have fundamental advantages over liquid crystal (LCD) screens, as they are based on a different functioning principle. Liquid crystals work like a sun-blind switching light, that is irradiated from the background, on and off for the observer upfront. OLED displays do not need a backlight, as each specific diode emits light when fed with electric current. A dark pixel in an LCD is only overshadowed, whereas an OLED display pixel is simply switched off. An OLED display is, therefore:
- More energy-efficient than a back-lighted LCD display, especially when the image content contains fewer light images, as is often the case with movies.
- Sharper contrasting than a conventional back-lighted LCD display. OLED displays achieve contrast levels of up to 1,000,000 to 1.
- Very thin, as there is no need for back-lighting. Manufacturers have already introduced three millimeter thin OLED screens.
- Very environmentally compatible, as OLED functional layers are only a few nanometers thin and contain no polluting substances.
Until now, however, these advantageous properties were applied to rigid substrates such as glass plates. “Manufacturers are working under full steam to apply OLED to flexible substrates – preferably in mass printing processes”, says Dr. Udo Heider, Head of the OLED division at Merck KGaA in Darmstadt, Germany. Challenges lie, for example, in the choice of a suitable printing technology or in the chemical formulation of high- performance inks, “because printed OLED has to meet the high standards of LCD displays as far as resolution, luminosity and durability are concerned”, says Heider.
For full report please visit LOPE-C