HP Laboratories Bristol has developed a prototype of a display that is
bistable, color, plastic and is made by imprinting and lamination
processes that eliminate the expensive vacuum deposition and photolithography
used to make today’s flat panels.
The 3cm x 4cm, 128 x 96 x RGB
prototype liquid crystal
(click to see prototype) does not require an active matrix
and can display 125 colors. The technologies used to create the
prototype are at an early stage, but are designed to scale to paper-like
resolutions over large areas so that future products can affordably
deliver full-color, print quality from a low-cost printed display.
The development is targeted at applications such as electronic
books and magazines and digital posters and photographs, rather
than video displays such as TVs and computer monitors.
pixels for ‘printed’ material
Current display technologies have price and performance
points that suit them to high-value products such as notebook
computers, televisions and mobile products including PDAs,
mobile phones and digital cameras.
The primary focus for
these products has been to create displays that are video-enabled,
and which usually have fewer than 2 megapixels. In contrast,
current printers support fine detail and crisp edges using
20 to 40 times the number of pixels per unit area compared
with the average computer monitor and can deliver this resolution
over large areas.
The prototype HP Labs display is a bistable
passive matrix, which means that displays with as many pixels as
desired can be built. Most of today’s LCDs have an active matrix
-- a TFT (Thin Film Transistor) embedded in each pixel to keep
it turned on between periodic updates. In the HP Labs prototype
the pixel stays on or off without this help, remembering its state
for as long as required.
Paper-like display technologies are beginning
to emerge, but so far many developments still need active matrices
and have focused on reflective, black-and-white displays.
and more content is produced in color. New display technologies
cannot afford to ignore that if they are ever to compete with books,
art, magazines and posters,” said Adrian Geisow, manager of Displays
Research, HP Laboratories, Bristol.
Low cost, large area manufacturing
Current flat screen displays are made on glass by processes
very similar to those used for making silicon chips. As displays
get larger, the factories to make them have become extremely
The new HP Labs prototype has been created out
of plastic, which is easier to handle than large sheets
of glass, and which reduces the weight and thickness of
the display. However, it is more difficult to make good TFTs
on plastic, so eliminating them avoids this problem and
the costs associated with the complex manufacturing processes
In the HP Labs prototype, the ability of the pixel to remember
its state is produced by tiny posts less than a thousandth
of a millimeter wide, which are imprinted on to the plastic.
These posts hold the liquid crystal in one of two orientations,
corresponding to ‘on’ and ‘off’.
The display also has electrodes that are integrated with the
printed color filters, further simplifying the device. The
electrodes and color filters are made by imprinting shapes
on to the plastic, and then using the shapes as templates for
the color filter and electrode materials. This gives very
precise control of features – such as metal lines five
“All of the patterning in the prototype has been carried
out by printing-like processes,” said Geisow. “The
details of the processes are still being developed, and we
expect it will take a few more years of further applied research
to properly develop and assess their commercial potential."
Given HP’s position in the printing and imaging
business, and the volume of display products that the company
sells, "any development that can deliver thin, light, and attractive
displays at low cost is of great interest," he said. "This
is particularly so if it can display images that would otherwise
need to be printed. We believe that this is an important advance.”