The newest generation of ‘borderless' smartphones are now available to consumers worldwide. Apple's iPhone X, the newly announced borderless smartphone, will be shipped in early November, and Samsung's Galaxy S7 has been available since March 2016. Why are borderless smartphones an important improvement over current smartphones? More display area means more information and less scrolling - or in other words, you see more information faster!
A borderless smartphone takes more engineering effort than one may expect. A borderless phone requires a flexible OLED panel in order to fold the display contacts underneath it. Until recently, these were prohibitively expensive, but more smartphone brands will introduce borderless displays in the coming year. What will be the next ‘big thing' for display technology? Smartphone giants are betting on foldable OLED displays.
Foldable screens will mean that engineers can design screens the size of a tablet (or larger) that can be folded to store in your pocket. These foldable displays have been promised to the consumer market for almost a decade - will smartphones with foldable displays actually ship anytime soon?
The challenges of foldable OLED
So far, the development of practical and affordable foldable displays has proven difficult for the industry. A significant number of the components in the smartphone must be able to fold and unfold thousands of times without breaking; not only the screen. These durability requirements bring an enormous engineering challenge to the phone industry. Smartphone engineers must calculate numerous different stresses when a component or film is folded many times. Suppliers must turn to fundamentally new materials and chemistries that can deliver components that are made out of thinner layers, films or even coatings than ever before while exhibiting significantly enhanced durability. In addition, industry engineers must develop new processes and equipment to manufacture these components that can take years to perfect.
Steady progress is being made towards a truly foldable commercial display; industry experts predict that a new generation of smartphones able to truly ‘fold up' will be on the market by 2019. A critical component of OLED displays is the circular polariser, which enables a key part of the screen to pass the rigorous folding durability tests. San Francisco-based Light Polymers, a nanochemistry company, has been working the circular polariser for the past three years.
The polariser is a crucial component of any LCD or OLED display. Simply put, polarisers partially filter light. LCD displays use two polarisers, front and back, which ‘filter' the light to a completely black colour when the display is off, and partially allow different colours of light through when the display is on.
In an OLED display, a front polariser is necessary to reduce the reflections of ambient or natural light that strike the front of the display. Without it, you could not see the information on the screen and it would look like a mirror with faded colours showing.
Today's polarisers use poly-vinyl alcohol (PVA), which is a 40-year old technology. Typically thick and brittle, PVA polarisers are difficult to manufacture in a thin format, are subject to UV cracking, and have inherent stresses due to the stretching that is part of their manufacturing process, which limits their foldability. PVA polarisers also pose manufacturing challenges because they are difficult to apply without defects.
A foldable solution
A different option is to base the polariser on lyotropic liquid crystals. These materials can be used to create circular polarisers that are both very thin and pass intense folding durability tests. Light Polymers' lyotropic liquid crystals are water-based and do not require special application equipment, high processing temperatures or physical stretching to manufacture the films or apply the material as a coating.
These liquid crystals have been called a ‘next-generation' technology; not only are production costs lower, due to their ease of manufacturing and simple application, but they are also self-aligning, meaning that the internal inter-molecular structure aligns without any additional processes when coated. They can be coated using a water-based system at ambient conditions, without the need to tightly control temperature and humidity.
Like any new material technology, coatings and films based on lyotropic materials require many years to develop and perfect, but companies like Light Polymers have achieved a process quality very close to production levels.
There are predictions that manufacturers will demand more than 40 million m² of OLED circular polarisers, to supply OLED smartphone displays and HDTVs, by 2021. How much of this production will be foldable screens? We cannot know yet, but by looking at past trends we note a similar situation that was a big surprise to industry marketers recently.
Many thought that smartphone consumers in Asia would not upgrade devices simply to get a larger display. Despite this, consumers bought larger smartphones in massive quantities, ensuring that phone models with screens over 6 in. use their size as a selling point; marketers did not account for the fact that so many smartphone users in Asia use their phone as a computer and want to be able to see more information. The market has proven to be more complex than marketing departments realised, leading to trends that no one expected.
Bigger screens mean more information and less scrolling, and foldable materials remove the brittle glass from the display, making it more durable. Does this mean foldable displays will catch on? It is likely that they will, and the question now is ‘At what price?' We'll have to wait and see.
Dr. Evgeny Morozov is head of product solutions at Light Polymers
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