The human-machine interface (HMI) will be a focus for automotive manufacturers in years to come, as they strive for closer connections between driver and vehicle.
Analog dials and buttons have given way to digital displays as seamlessly integrated smart surfaces. But manufacturers are dealing with more complex material issues to solve designers’ demands for sleeker solutions.
Display makers want the freedom to reimagine the driving experience. They want more choice over materials, cost-saving processes, and a seamless, flowing route around the controls. But designers also need to protect the most sensitive components inside the display.
Without UV protection, displays will lose brilliance and quality of image, and the material itself will degrade, potentially even yellowing over time. A polarizer film is the piece most commonly used in the display stack to block out the worst of the UV light. But a polarizer’s thickness – just a fraction of a millimeter – can still add unwanted thickness. Furthermore, its relatively low aging performance – particularly at temperatures above 95°C – leaves engineers in search of an alternative.
However, tesa has produced an Optically Clear Adhesive (OCA) that combines adhesive strength with added properties such as UV resistance. Testing shows our tesa® 88910 adhesive material blocks transmittance of UV light below a wavelength of 380 nm, while achieving a transmittance of visible light over 99 %. A UV-vis spectrometer was used to gather results, at conditions of 23 °C and 50 % RH. Only the adhesive itself was tested, without a liner or glass.
YuKun Wu
tesa® Greater China
Our partners within the automotive industry provided the insights to help us come up with a solution: an OCA that conforms to leading standards in UV protection, while remaining versatile enough to shape into innovative display design.
We tested our tesa® 88910 OCA tape against DIN 75220, simulating long-term outdoor exposure, to check its ability to minimize yellowing of the OCA itself and all components behind it – a common effect of UV light. We found no visible increase in yellowing of the OCA.
This testing process also highlighted the other functions in which our OCA demonstrates tremendous quality – low haze allowance and comprehensive ink step coverage while keeping a slim design..
Low haze is another requirement of display manufacturers, who need materials that transmit as little light through the layers as possible. Our testing in accelerated weathering conditions showed haze below 1 % – well within acceptable parameters, and with no visible effect on display quality.
Another big ask which we can deliver for automotive manufacturers concerns ink step coverage – a crucial capability to prevent failures between the black printed frame and the transparent part of the cover glass.
Dolly Cheng
tesa® Greater China
As the display industry evolves, so too will design needs. That is why we are always challenging our assortment of OCA products. Sustainability is an important factor as it encourages responsible re-use of materials. To that end, there is an increasing need for reworking and recycling materials where possible. Our assortment of OCA products can meet that need.
We have worked with leading automotive display makers around the globe to learn and understand the challenges of manufacturing a quality, innovative solution for UV exposure. We are confident our assortment of UV-resistant OCA products meets those requirements, helping customers to create ambitious, long-lasting HMI designs, built to beat the elements.
This piece was written in conjunction with Dolly Cheng, Market Segment Manager; and YuKun Wu, Product Development.
