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Topics Covered
Background
Touch-Screen Technology Market
Overview
Material Selection for Touch-Screen Display
Resistive Touch Technology
Capacitive
Touch Technology
Alternative Touch Screen Technology
PEDOT Formulation
Carbon Nanotubes for
Touch Screens
Other ITO-based Formulations
Future Market of ITO
Background
NanoMarkets is a leading provider of market and technology
research and industry analysis services for the thin film, organic and printable
electronics businesses (which we refer to as TOP Electronics.) Since the firm
founding, NanoMarkets has published over two
dozen comprehensive research reports on emerging technology markets. Topics
covered have included sensors, displays, OLEDs, HB-LEDs, e-paper, RFID,
photovoltaics, smart packaging, novel battery technologies, printed
electronics, organic electronics, emerging memory and storage technologies
and other promising technologies. Our client roster is a who who of companies
in specialty chemicals, materials, electronics applications and manufacturing.
NanoMarkets also hosts a blog at www.nanotopblog.com where we
discuss technology trends, company announcements and the industry on-going
progress.
Touch-Screen Technology Market Overview
Touch-screen
technology, already widespread in applications ranging from PDAs to checkout
displays, has become even more popular since the introduction of novel consumer
electronics such as Apple's iPhone and follow-on clones. According to a report
published by NanoMarkets, The Future of ITO: Transparent Conductor and ITO
Replacement Markets, March 2008, as much as $118 million in transparent
conductor will be sold into the touch-screen market in 2008, rising to $400
million by 2015.
Material Selection for Touch-Screen Display
Transparent conductors combine the electrical conductivity of metal with the
optical transparency of glass. They are the ideal material for touch screens,
since they make for nearly invisible electrical traces. The dominant transparent
conductor is indium tin oxide (ITO), which is
found in nearly every touch screen on the market today. Unfortunately, it's the
optical electronics version of a shampoo-conditioner: While it possesses both
properties, it doesn't perform either one to optimal standards.
In addition, while demand for indium keeps increasing, sources for it are
limited, leading to fears of rising prices and short supply. Given the
proportionate amount of ITO in touch screens, higher indium prices
could have a significant impact on total materials costs. Those concerns have
led the Indium Corporation to put a disclaimer on its Web site reassuring
customers of continued supply at reasonable prices.
More critically, ITO is brittle, and often cracks from overuse, yet touch
screens are now employed in a wide variety of medical devices. For example, the
state of the art surgical suites at UCLA's newly opened Ronald Reagan Medical
Center feature touch screens that allow surgeons to adjust viewing angles for
laparoscopic surgical tools. In such a situation, the stakes for a cracked ITO rise from
merely annoying to possibly life-threatening.
Given all of that, touch screens are the most tempting target ITO
replacement solutions.
Resistive Touch Technology
The two primary touch-screen technologies in the marketplace are "resistive
touch" and "capacitive touch." Resistive touch
screens, about 90 percent of the current market, have two ITO layers
that must be pressed together to make electrical contact, which then activates a
controller. The screen interface is a protective outer layer onto which pressure
is ideally applied with a soft stylus. Unfortunately, under real world
conditions, pressure is often applied with pens or sharp fingernails, shortening
the life of many resistive touch displays. But even when pressed only by a
stylus, they often crack after repeated flexing.
By contrast, capacitive touch screens, employed in devices like the iPhone,
are activated by lightly brushing a finger on the screen, eliminating the
possibility of cracking (providing the device isn't dropped). In this way, they
use the body's own conductance to shift the stored electrical charge
(capacitance) of the device. When the screen is touched by a finger or hand, an
ITO
substrate detects the change in the capacitive field, which activates the
controller.
Capacitive Touch Technology
Capacitive
touch is often called "multi-touch," since several fingers or even full
hands can be used to direct the devices. New terms may emerge as more
trademarked devices are developed. Microsoft, for example, has a tabletop capacitive touch
screen it calls "Microsoft Surface." Depending on the sophistication of the
underlying programming, capacitive touch also allows for much more fluid
navigation than "press here" resistive screens, such as the iPhone's ability to
"zoom in." In the next few years, capacitive screens will make serious in-roads
into sales of resistive touch screens.
Due to their tendency to crack, resistive touch
screens are the leading edge of the ITO
replacement market. In addition, since ITO is used as
part of the flat panel display in all touch screens,
as well as the electrical control, it would be advantageous to have a ready
supply of an alternative material.
Alternative Touch Screen Technology
There are four areas in which the alternatives compete: price, conductivity,
transparency, and resiliency. Although several alternatives score well in two or
three areas, none have yet scored on all four. More challenging, many are still
in the development phase.
Other transparent conducting oxides (TCOs) might
seem a good place to start, since they often cost less than ITO, while
possessing its favorable characteristics (transparency, conduction).
Unfortunately, they share its worst one as well: They tend to crack under
repeated use. If researchers improve the electrical conduction of alternate TCOs, they may
find a home in some applications, but they would not be an improvement for touch
screens.
Of the potential ITO replacements, perhaps the best known is the conducting
polymer PEDOT Poly(3,4-ethylenedioxythiophene), which has already been used by
Fujitsu to build touch screens. The good news is that it is both more flexible
and far cheaper than ITO, at only about ten percent of its price. The bad news is
that conductive polymers are less conductive than metals. Nevertheless, doping
and other laboratory strategies can be used to improve their conductivity. But
even with improved chemistry, PEDOT can degrade under UV light.
PEDOT Formulation
H.C. Starck markets a proprietary formulation (PEDOT:PSS) under the tradename
"Baytron," which is a compound of PEDOT with polystyrene sulfonic acid. Starck
says its latest version has conductivities that equal some metal oxides. But, at
conductivities of up to 500 C/cm, it is still an order of magnitude less
conductive than ITO (6000 C/cm). PEDOT:PSS is a likely leading contender in the
replacement market because it is highly transparent and thermally stable in
comparison to other polymers. In addition, the potential is there to tweak the
formula to further increase its conductivity without degrading its
transparency.
Carbon Nanotubes for Touch Screens
Despite hope for a new kind of electronics based on carbon nanotubes (CNTs),
so far they are still more in the research phase than the application phase. If
they advance, they have several advantages for touch screens. They are highly
conductive and flexible, and would be relatively transparent at the necessary
densitiesaking for good, potential ITO replacements. Companies such as Eikos
and Unidym are pouring a lot of resources into developing commercial carbon
nanotubes, but nothing yet exists that would transform the touch-screen market.
Unidym is working on a CNT-based conductive film, which it plans to market as an
ITO
replacement in touch screens and other displays. The company plans to jointly
develop touch screens for the video game industry with Japanese manufacturer
Touch Panel Laboratories. However, in the immediate future, carbon nanotubes
likely will be most often used for electrostatic coatings, according to
Eikos.
While there are other nanomaterials that are not specifically nanotubes, none
have made it to the marketplace. Companies doing research in this area include
Sony, DuPont, and Cambrios, co-founded by MIT professor and MacArthur Award
winner Angela Belcher. Still, this area leaves room for optimismoth carbon
nanotubes and other nanomaterials are the only areas where truly novel,
market-changing technical breakthroughs could occur. One example is the metallic
nanowire arrays developed by the lab of L. Jay Guo at the University of
Michigan. They are ductile, flexible, and conductive; their mesh-like structure
gives them transparency. Guo is now considering researching their potential use
in touch screens.
Other ITO-based Formulations
These are not replacements, per se, but re-workings of traditional ITO manufacturing
processes, such as ITO nanopowders and ITO inks. Most
are still in the research phase, and while they may eventually offer flexible
solutions to fabrication, they have not overcome ITO's
traditional problems.
Future Market of ITO
ITO is
likely to dominate the touch-screen market for the foreseeable future.
Nevertheless, since there are good reasons to find a replacement, NanoMarkets
predicts that by 2015, ITO will only be 44.8 percent of the market. By 2015, we
believe the top three replacements in order of market penetration will be:
organics (PEDOT) at 18 percent; carbon nanotube-based formulations at 15
percent; and other nanomaterials at 9 percent.
Source: "The Future of ITO: Transparent Conductor and ITO Replacement Markets", Market Report by Nanomarkets
For more information on this source please visit NanoMarkets