DISPLAY TECHNOLOGY AUTOMOTIVE DISPLAYS
A finger on the pulse of time
S martphones, tablets, televisions:
touch displays are ubiquitous
and are increasingly being
used in modern vehicles - whether
for buttonless operation of the air
conditioning or infotainment system.
In contrast to consumer
electronics, these functions have to
face special challenges in vehicles
from strong vibrations and changing
temperatures to electromagnetic
fields. In order to ensure that
drivers can enjoy the benefits of
touch displays, the technology
must therefore be adapted to the
requirements of the automotive
industry. This is achieved, for
example, by integrating state-of-theart
technologies with TDDI or OLED
components, but also by means of
an extensive testing and validation
process with regard to resistance and
function.
In this way, it can be ensured
that the driving experience is actually
enhanced and not diminished by
advanced touch displays.
Capacitive sensors are used for
touch displays due to their higher
reliability and wider range of functions.
While panels in household electronics
are becoming thinner and lighter, this
poses a greater problem for vehicles.
There, the sensitive sensor technology
is subject to stricter requirements in
terms of service life and environmental
influences, which is why more robust
displays have been developed -
but at the expense of lightweight
construction. Nevertheless, precise
sensor technology is still necessary in
vehicles in order to provide the levels
of comfort that are associated with
modern vehicles.
While high rigidity of components
is also important, touch displays
should still be flexible enough in an
accident to reduce the risk of injury in
a collision. It is therefore important to
protect the sensors and the driver on
How are features associated with interactive displays finding their
way into the passenger cell of the future? By Sebastian Masi
Author details:
Sebastian
Masi is Senior
Engineer Display
& Instruments at
ARRK Engineering
protected at the top by a cover glass.
The deeper the sensor technology
is built into the cell, the more the
surrounding components offer
protection – and a slimmer, thinner
design becomes possible.
Limiting the number of layers, in
the optical “stack”, results in lower
reflection and improved solar radiation,
without increasing the brightness of
the backlight.
Initially, the so-called outcell design
was common for the development of
touch displays. Here, the display was
connected to the sensor by a bonding
process. The biggest advantage of this
design is that any display technology
preferred for the application can be
used. For example, any commercially
available touch sensor that meets the
requirements can be combined with
the display. However, this means that
the sensor technology rests externally
on the polarisation filter, which makes
the entire component thicker than is
desired in consumer electronics.
In order to counteract this
disadvantage of the Outcell design,
the Oncell design was established
the one hand, but also to bring familiar
features into the passenger cell on the
other.
Outcell, Oncell, Incell
This can be achieved by integrating the
individual components into the display.
When the electronics are applied to
the outer layers (Outcell Technology),
they are more exposed to temperature
fluctuations, vibrations and
electromagnetic fields. As a result,
the sensor and the microcontroller
need to be built deeper and deeper
into the panel (Oncell technology).
The advantage of such a design is the
basic structure of a touch component:
the heart of every touch LCD display
is the so-called cell, which essentially
consists of a protective TFT glass layer
(Thin Film Transistor) on which TFT
circuits are mounted.
Above this is a layer of liquid
crystals, which is closed at the top by
a colour filter and the corresponding
glass layer. This entire element
is enclosed by the polarization
filter. From below, the display is
supplemented by a backlight, and
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