Date:1st Nov 2011
Sensor-on-cover and in/on-cell are emerging
tech in capacitive touch panels
DisplaySearch has announced its latest research study
on capacitive touch panels. The release from DisplaySearch
states In-cell and on-cell sensors are typically integrated
during the display manufacturing process, whereas sensor-on-cover
involves coordination between touch sensor and cover glass
makers. While Apple products use glass-based sensors with
ITO (indium tin oxide, the typical transparent conductor)
layers on both sides, most sensors use one or two layers
of ITO on the same side of the glass; this is required for
sensor-on-cover because the outer side is the exterior of
the product, said in the release.
Jennifer Colegrove, PhD, Vice President of Emerging Display
Technologies for DisplaySearch says "Two approaches
are emerging to simplify projected capacitive sensor designs,".
"One is sensor-on-cover and the other is in/on-cell."
The other research finding shared by DisplaySearch includes:
Capacitive touch screen shipments grow by more than 100%
Y/Y, cover glass has become a key component in touch screens.
Regardless of the type used-sensor-on-cover or in/on-cell-cover
glass is a must for projected capacitive touch for both
cosmetic and protection purposes.
Cover glass finishing is very labor-intensive and, depending
on the processes required and specifications, has yield
rates in the 70% range. Process challenges will be an increasingly
strategic issue for the industry. Depending on the technology
and supply chain, cover glass finishers and touch module
makers will be working together by contract or informal
relationship, while tier-one touch module makers are integrating
and expanding their in-house cover glass finishing capacities.
The touch screen supply chain is evolving differently in
each region, based on variations in technologies and supply
chain variables. Although sensor patterning and lamination
processes are mostly automated, manpower is still necessary,
especially for inspection. Japan, with high labor costs
as well as a complex supply chain, tends to have the highest
cost structure. China offers the lowest prices for mature
mobile phone sensors, and Taiwan has lower prices for tablet
PC sensors. This is due to greater availability of glass
and better access to Gen 4.5 and larger equipment for sensor
deposition and photolithography.
For popular mobile PC sizes (9.7" and 10.1"),
average selling prices (ASPs) per unit are in the range
of $1.00-1.50 per inch; however, DisplaySearch anticipates
ASPs will fall as popularity increases. ASPs of regular
notebook sizes (>11.6") are still higher due to
challenges in scaling production.
Curved or shaped cover glass-referred to as 2.5D if along
one axis and 3D if along both axes-is a new design trend.
Many touch-enabled smart phones look very similar, so brands
are looking to use curved cover glass to differentiate their
products. Due to its more complicated processes and costs,
DisplaySearch expects curved cover glass to be used primarily
in high-end models.
While touch module makers are likely to outsource larger-sized
sensors if volumes increase, DisplaySearch expects tier-one
touch module makers to integrate cover glass finishing because
it is critical for sensor-on-cover production and for decreasing
substrate weight and thickness.
Moving into the holiday season, DisplaySearch forecasts
that the tablet PC market will be increasingly important
for the touch panel industry, particularly as lower-priced
products, like the Amazon Kindle Fire, enter the market.