What is the future of foldable phones? We’ve heard how flexible displays would be the future of smartphones and tablets since 2013, when Samsung showed its ‘Youm’ display at CES, but it wasn’t until last year that we got to see such displays in a real product that was not just a concept.
But in a short space of time, the folding display technology seems to have matured enough that LG even made a roll-up TV last year, which was the highlight of its stand at CES 2019. While all of this is great, the foldable OLED screens are delicate on their own, which means they still need a layer of protection over them if they were to be used in the real world, like in a smartphone. For this we need glass that can bend.
So far, all of the foldable phones we’ve seen have used plastic protective layers over the OLED panel for basic scratch protection. However, these are clearly not enough for long or even short term sustainability. Take last year’s Samsung Galaxy Fold, which failed miserably in a durability test. The Motorola Razr (2019) also had multiple reports of failure, with the screen falling apart within a week of use until the hinge gave up after just four hours of opening and closing.
The first phone with a folding glass display was this year’s Samsung Galaxy Z Flip. It certainly felt like the real deal when we first tried it during the launch event, with no real signs that the screen was fragile or delicate. However, it turned out that even this wasn’t nearly as durable as today’s regular scratch-resistant glass, and in one durability test it fared just as badly as the Galaxy Fold and the Motorola Razr (2019).
Challenges in making collapsible glass
Folding glass or ultra-thin glass (UTG), as used in the Galaxy Z Flip, is still a first-generation product, meaning it still has a long way to go before such glass can be as durable as the glass being used on regular phones today, while still being flexible.
“Thickness is the key difference between flexible and traditional flat glass, in addition to some special” magical ingredients, “said Mathias Mydlak, Global Business Development Manager at Schott.
Bendable glass is essentially glass that has been stretched thin enough and then treated so that it can bend back and forth without permanently losing its shape. Making glass thin to the point where it is flexible, however, is the biggest challenge, according to Mydlak. “We define ultra-thin glass (UTG) by reaching a thickness of less than 0.1mm,” he added.
Schott claims that UTG glass has been used for other applications in recent decades and has a specially developed “down draw process”. Here a glass ribbon is pulled from top to bottom, over several drums and through a cooling track to get the final product.
Schott is one of the few glass manufacturers that already has a flexible glass solution on the market. Samsung is one of its customers, which means that the UTG glass in the Galaxy Z Flip is most likely supplied by Schott. Corning would also partner with device manufacturers to implement its own solutions. “We are working on this challenge with our customers and are currently taking our development glass to optimize the product for their design requirements,” said a Corning spokesperson.
Is it as durable as ordinary tempered glass?
So far this does not seem to be the case. If we take the Galaxy Z Flip as an example, the durability test of a popular YouTube channel showed that the UTG glass scratched as easily as the plastic screens on the Galaxy Fold and Motorola Razr (2019). In fact, a powerful dash made by a fingernail also seemed to leave permanent marks on the screen.
Schott argues that the scratch resistance of foldable glass is in the comparable range of normal, thicker glass, and it all depends on the curing process. “The curing processes are carried out by separate glass processing companies. So it ultimately depends on their individual processing steps and recipes, ”said Mydlak. This means that although Schott or Corning can supply the raw materials, the toughness or durability still depends on what kind of treatment it is given by the phone manufacturer, for now.
Corning, on the other hand, believes there is still a lot of work to be done before foldable phones are as durable as regular phones. “In general, we believe that current material sets of plastic options and glass options do not meet all the desired properties of a flexible device,” said a Corning spokesperson. However, Corning states that the folding technology has shown success in the 30-100 micrometer thickness range in its R&D.
In addition to being scratch resistant, the biggest durability issue of folding glass is the ability to maintain structural integrity even after years of folding and unfolding. Corning claims that the glass-based development solution can bend more than 200,000 times without causing damage while maintaining flatness. Meanwhile, Mydlak stated that the life of the folding glass ultimately depends on the final design and processing performed by the device manufacturer.
Another issue commonly found with foldable devices is a visible crease in the fold, which is natural, but also detracts from the feel of a completely flat screen. While this has more to do with the actual foldable display panel itself, in such phones that now have a glass cover, it is important that the glass also show minimal wrinkle.
“We have seen that the fold has already decreased after switching from polymer foil substrates to UTG as a premium substrate. In fact, this is great proof of the potential of this material class, ”said Mydlak.
Making foldable glass is also understandably more expensive than regular glass of the same size. While Mydlak didn’t say exactly how much more expensive it would be, he did say both could be on a similar level at some point in the future, provided enough people buy appliances with foldable glass.
We don’t expect folding technology to become mainstream anytime soon, but that doesn’t mean it won’t. There was a time, not so long ago, that even flagship phones came with just one camera, and today most of us won’t even look at the budget phone if it doesn’t have at least three cameras, and that’s just on the back.
“With each new development or technological advance, all players eagerly assess growth trends and consumer preferences,” says Mydlak. “As it gains popularity and we see a massive demand for collapsible glass, the product will automatically become more cost effective and accessible,” he added.
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