Automotive Engineering - June 2020 - 28

Q&A
New polycarbonates provide 'sensor transparency'

The term 'optical purity' is used to
describe requirements for advanced
headlamp modules that incorporate
forward-looking sensors. What's
your take on that?
Optical purity of the sensor's cover
lens, or any surface that protects an
optical sensor, is important for that
sensor's acuity. With lidar for example, as the emitted light passes
through the cover lens and returns,
any impurities in the material can degrade the fidelity of the signal itself.
We're developing solutions to improve the purity of our polycarbonate
materials, not only the grades but
also the coloring systems.
Then you must validate it.
Yes, and because it's a safety-related
item it requires more time to validate.
Some developers who didn't think
they needed the higher-performance
material have observed what I'll call
'application-level' defects.
Traditionally in automotive you start
with the lower-cost materials and see
if they work, and we've already had
people who found that they really do
need the more optically-pure polycarbonates and come back to us with
that request.
Exterior designers say integrating
lidar into the bodywork is a looming
challenge.
For integrating lidar, we now have sensor-transparent grades of material. We
have had our AL [automotive lens]
grade used in headlamps for years. We

28 June 2020

Covestro's
Paul Platte

enhance that to achieve higher purity, toward an AX [exterior
polycarbonate family] or an Ai if it's in the interior. But to have
sensor transparency, you also must consider the base material
and color combinations. Making something that looks simple and
homogeneous can be challenging. Designers want their new displays to appear 'hidden until lit.' They want a deep, glass-like, piano-black surface until it's back-illuminated. Sometimes the items
behind that surface are translucent, transparent, or opaque, requiring three different color matches to sustain a consistent surface appearance. In increases the materials complexity three-fold.
Our sensor-transparent polycarbonate grades are designed to be virtually opaque to the
human eye, with the rich high-gloss
finish, while they're actually transparent to lidar's 905- and
1550-nanometer wavelengths. This
is where OEMs are headed now, in
terms of hiding their sensor arrays.
And located next to that lidar behind the front-end panel, you might
have a headlamp whose light must
shine through. And next to the hidden headlamp you might have a
micro-LED or OLED display. Those
displays are offering increasing resolution. The industry is taking technology from consumer electronics
and bringing it into automotive.
Covestro's approach is we want to
work with customers on whatever
route they take

"New material grades
that are virtually
transparent to lidar's
wavelengths are where
OEMs are headed now."

Is the trend toward larger UX displays in cabins driving more focus on
greater polycarbonate acuity?
Yes. Internally we talk about a threedimensional surface that has radius of
curvature in two directions, like a
horse saddle. And those radii are getting tighter and tighter. That solution
is viable in polycarbonate. It's been
part of our polycarbonate-windows
discussion for a while. That kind of
surface form factor is coming to both
interior displays and to the large
front-end panels of electric vehicles,
as shown in concept by Mercedes,
BMW and others. That surface is going to have sensors and displays behind it - the exterior displays being
used for differentiation and for pedestrian protection.

AUTOMOTIVE ENGINEERING

COVESTRO

The sensor arrays that currently reside on the roofs of development mules will be hidden from view on future production
vehicles. But how to conceal them without affecting their
safety-critical performance? This design and engineering
challenge, along with the growing trend toward larger, multifunction interior and exterior displays, is driving new polycarbonate solutions at Covestro, which was spun off from Bayer
Materials Science in 2015. For insights into this new family of
materials, editor Lindsay Brooke spoke with Paul Platte, a mechanical engineer by training who now is part of Covestro's
marketing team.

Automotive Engineering - June 2020

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