Making OLED Display Manufacturing Easier

Using its proprietary inkjet technology, Epson has overcome a major obstacle
to manufacture large-sized OLED displays. Outstanding characteristics like high
contrast, wide viewing angle and fast response time, makes OLEDs the next choice
for display technology.

Every company that manufactures LCD has some research and development being
done on OLED displays. And this does not come as a surprise, as OLED is the
display of the future, and is all set to replace LCD.

The simple structure of an OLED matrix displays makes it highly scalable and
flexible. Besides, OLED display is believed to be much cheaper to manufacture
than plasma display of large sizes.

Organic LEDs are luminescent plastic semiconductors with the theoretical
potential to replace LCDs, CRTs and other display technologies through greater
efficiency, easier production, more physical flexibility and lower cost.
However, until now, technological barriers like device lifetime, chemistry and
production limit had slowed development of OLED.

While many companies have already come up with stunning prototype of OLED
displays on cell phones and other portable devices, the technology used by Seiko
Epson for its OLED panels appears to be the most interesting. The proprietary
Micro Piezo inkjet technology used in their printers has come handy for making
OLED matrix displays.

HOW EPSON DID IT?

Epson's high-performance Si-TFTs, flexible electronics technology, the
micro liquid process (a specially adapted form of inkjet printing), ultra-low
cost digital memory and radio frequency technology for interfaces, all have high
potential for use in the displays of the future. Using this technology, Epson
developed the world's largest (40-inch) OLED display prototype. The prototype
is an example of how much Epson has progressed in the development of OLED
display.

Epson's smaller prototype of OLED display

Seiko Epson has produced three prototype displays. According to the company,
the 40-inch model unveiled in May had wide-screen XGA resolution (1280RGB pixels
by 768 pixels) and a pixel density of 38 pixels per inch (ppi), a 12.5-inch
model has VGA resolution (640RGB pixels by 480 pixels) and a pixel density of
64ppi and a 2.1-inch model had a 144RGB pixel by 176 pixel resolution and a
pixel density of 130ppi.

WHY INKJET FOR OLED?

With many years experience in the inkjet printer business, Epson already
possesses a great deal of knowledge about the possibilities of inkjet. Combining
this experience with its original Micro Piezo inkjet technology puts Epson in a
unique position.

Unlike competitive inkjet systems that use heat, Epson's Micro Piezo system
fires its ink by applying a current to a piezo element, which oscillates
precisely according to the strength of the current. Not using heat greatly
increases the type of substances that can be fired, a fact that has led Epson to
experiment with a variety of materials such as the organic substances used to
create OLED (organic light-emitting diode) displays.

The market for large displays is changing rapidly, as consumers switch from
rigid CRT type TVs to flat-panel TVs. Although it may take some years for Epson
to turn this prototype into actual products, the company possesses a number of
core technologies that may one day turn its dreams into a reality.

Epson was already looking beyond flat-panel TVs by leveraging its core
technologies to explore the possibilities of flexible displays - including
e-paper. The company believes that new technologies will improve the
functionality and versatility of displays, thereby increasing the number of
display applications in our daily lives.

THE NEXT BIGGEST OLED

As the technology and tools to manufacture OLED are getting better, there
are other players as well who have announced prototypes of OLED display.
According to reports, Samsung SDI, the Korean giant's display division, has
announced prototypes of a 17-inch active matrix organic light emitting diode (OLED)
display. This is probably the next largest display after Epson's.

The display has a resolution of 1600x1200 pixels and a brightness of 400
lumens. Samsung's basic OLED technology was licensed from Kodak and developed
in conjunction with NEC, which sold its stake in the joint venture to Samsung at
the beginning of 2004. The displays are made using a transfer technology
developed by Samsung and 3M, where the pattern of plastic pixels on the screen
is printed by scanning a laser across a set of organic films.

While Samsung claims that this technology can produce a larger screen than is
possible by the alternative method of spraying the plastic through a patterned
shadow mask, Epson has proved them wrong by unveiling the largest OLED display
using inkjet technology.

Epson has been actively working to develop and commercialize next-generation OLED displays.  It has developed an original inkjet process for depositing organic layers on large-size TFT  substrates. Using this adapted inkjet technology to form organic layers on large-size substrates in a simple process, it has developed the world's largest (40-inch diagonal) full-color OLED display prototype in May 2004.

As the inkjet technology uses a push-pull-push mechanism instead of heat to
fire liquid on to any surface, it becomes easier for them to experiment with a
variety of substance. "Turning organic substances in to liquid and then
fire them on to different surfaces like plastic is easily done using Micro Piezo
technology, because it does not use heat and heat can melt plastic. In fact,
this technology can be used to manufacture many other semiconductor-based
products," says Masao Akahane, MD, Seiko Epson Corp.

FACED BY CHALLENGES

The challenge now is to make efficient transistors on plastic, so that the
displays will be bendable (flexible). While Epson has managed to develop
bendable display on plastic, the life of such display is still an issue. The
organic material used in the screens has a working life of up to 2000 hours.

Unless this touches about 10,000 hours, it will not be a viable replacement
for LCD or Plasma. However, the pace at which Epson is developing OLED display,
we can hope to see a much efficient product by the start of 2007 Olympics.

Epson is optimistic that OLED can be a bigger profit source for display
manufacturers, as it can be applied on to a variety of products which currently
is dominated by LCD displays. These are the 5-inch screens viz.: digital
cameras, mobile phones, photo viewer; the 10-inch screen: In car applications;
and the 50-inch screen for TV.

Epson believes that the characteristics of OLED displays make them the ideal
device for entertainment applications, whether in equipment for the road or
living room. The company is thus gearing up towards commercialization in 2007.

NELSON JOHNY in Suzhou, China. (The author was hosted by Epson India)