Exploring the benefits of organic electronics: Biaxially curved displays and optics

Paul Cain, Strategy Director

May 16, 2022

Probably every example of a flexible display you have seen is curved in a particular way – a so called “uniaxial bend”: if you shrunk yourself down, stood on the surface of such a bend and spun around on the spot, you would notice that in one direction the display is still completely straight.

Examples of surfaces with uniaxial curvature are cylinders and cones. All foldable smartphone displays are uniaxially curved.

However, many real-world surfaces are not so simply curved. They are often curved in all directions wherever you stand, like the surface of a ball, a doughnut, or a saddle. These are all examples of biaxial curves.

All displays today, whether flexible or not, are manufactured flat. If they are built onto plastic instead of glass, then they can be uniaxially curved by bending around a cylinder. FlexEnable’s glass-free OLCD technology has already been proven to enable curved and non-rectangular form factors with applications in consumer electronics and automotive. We’re now taking this technology to the next level by unlocking an even greater design freedom with biaxial curved displays – all enabled by organic electronics.

Making biaxial curved displays using organic electronics

Biaxial display speaker

In order to take something flat and make it biaxially curved, you must stretch it – both the substrate and all the active layers built upon it.

The high temperatures of conventional large area electronics means that substrate types selected need to have very high melting points so that they don’t distort or worse, melt, during the (flat) manufacturing process. This is one reason why glass is commonly used. For flexible OLED displays, high temperature polyimide is used because it has a very high melting point. However, that high temperature requirement of the substrate works against you if you want to then biaxially curve the substrate afterwards using heat and pressure – the substrate would need to be heated to such high temperatures that it would damage the active materials of the display. (Image: Visualisation of biaxial curved display - photo credit: FlexEnable.)

OTFT spherical structureOrganic electronics turns this argument on its head by exploiting the very low temperatures of organic thin-film transistors (OTFT) production – less than 100°C. Such low temperatures allow substrates with relatively low melting/softening temperatures to be used without being damaged during the (flat) manufacturing process. After production, the low melting/softening point of the substrate means that the device can be biaxially formed using much lower temperatures that are benign to the various materials in the device. At FlexEnable we have shown that both OTFT arrays and liquid crystal cells can be biaxially formed in this way, enabling active surfaces to be applied almost anywhere. In addition to OLCDs, examples include liquid crystal cells that modulate and steer light and can be biaxially formed to follow the complex contours of a car windows or the 3D curved surfaces of AR/VR headsets. (Image: OTFT structures formed across a spherical cap of spherical radius 130mm - photo credit: FlexEnable.)

If you are looking to reshape your product design, then please get in touch with FlexEnable at info@flexenable.com for more information

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