Thin displays on a roll
Philips has developed a technology which could eventually lead to the development of displays so tightly rollable that they could be stored in everyday objects as small as mobile phones and pens.
The company claims to have routinely produced prototypes of organic electronic displays on a wafer-thin foil and plastic substrate that can be safely rolled to a 2 cm bending radius.
The technology could eventually lead to the development of “unbreakable” displays so tightly rollable that they could be stored in everyday objects as small as mobile phones and pens, being rolled out as and when required.
The sheer portability and convenience of this technology means it could stimulate the advance of electronic alternatives to paper-based books and newspapers. Philips says the ultimate goal of this display technology is to make a display that resembles paper, in appearance, feel and optical character.
The prototypes have a 125-mm diagonal, 320 by 240 pixel active matrix Quarter Video Graphics Array (QVGA) and 85 dpi resolution. They combine a 25-μm thick, layered active-matrix backplane, containing polymer electronics-based pixel drivers, with a 200-μm plastic front plane of reflective “electronic ink” developed by specialist firm E Ink.
Electronic ink-based displays are said to be ideal for reading-intensive applications because of a paper-like readability quality.
Equally crucially for portable applications they have low power consumption: once an image is “written” it requires no further power to maintain it on-screen.
A key technical challenge Philips had to overcome in the development of these plastic displays was to find a way to robustly fabricate close to 80,000 polymer-based thin film transistors (TFTs) in a regular array with largely identical electrical characteristics. The TFTs are used to switch each display pixel on and off.
Another challenge was to produce properly functioning shift registers—an important building block of the polymer display drivers—that could be fabricated using the same process as used for the backplane TFTs.
This allowed the display drivers to sit on the same substrate as the display and resulted in a more reliable design and more compact footprint with fewer external connections.
The company says that it is capable of producing the displays on a routine basis—it can currently produce several units each week—and now intends to develop an industrially feasible production process.
9-Mar-2004