Checking in with Corning: the status of foldable glass

Last week, we had the chance to talk to Scott Forrester, Division Vice President, Marketing and Innovation Products at Corning. The company offered us a look at Corning’s history of glass and ceramic manufacturing, along with insight on the production of Gorilla Glass for smartphones.

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We had a chance to ask questions about Gorilla Glass and how Corning strikes a balance between scratch resistance and durability against shattering. We also asked about the progress of using flexible glass in foldable smartphones.

Finally, we checked in with Corning on its thoughts about Sapphire glass. If you remember, there were a few devices that used this more expensive but highly scratch-resistant glass like the HTC U Ultra Sapphire Edition, the rugged Kyocera Shield, and the Apple Watch Edition.

Introduction and brief history of Corning

Corning has been around since 1851 and it was first known as Corning Glass Works when it opened in Somerville, Massachusetts as glass became a more common raw material. Its first patent in 1877 was for railroad signal lenses with a smooth exterior that didn’t gunk up over time. In 1879, it developed the glass around the first Edison carbon filament before inventing a way to mass produce these bulbs.

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In 1915, Corning started the PYREX brand of glass cookware and would go on to mass-produce TV tubes in the 1940s, making TVs more affordable. In 1964, Corning scientists would invent a new process of forming glass in 1964 called “fusion overflow” that made ultra-flat panes pristine glass and would eventually become the process for LCD screens later in the 2000s.

In 2007, Corning’s CEO was contacted by Steve Jobs with specifications to develop a durable, thin, and lightweight glass for the first iPhone - this would be called Gorilla Glass. Over the last decade, Corning gradually developed thinner and lighter Gorilla Glass while retaining the same shatter and scratch resistance.

Today, Corning is continuously researching new glass compositions that could help make glass more resistant to scratches and drops. Now Corning is developing glass that could be used in the future generation of foldable smartphones.

Aside from consumer electronics, Corning manufactures glass for a wide variety of applications including optical fiber for high-speed communications, glassware for pharmaceuticals, manufacturing and packaging, and emissions-control products in the automotive industry. Corning employs 50,000 workers at 70 manufacturing and research facilities throughout North America, Europe, and Asia.

State of foldable glass, scratch vs drop, and whatever happened to sapphire glass

Foldable phones made their debut this year and based on the past several months, we have a feeling the trend is here to stay. These displays are all currently covered in plastic since it's immediately available and easy to mold to the foldable form factor. The downside to plastic is that it scratches much easier than glass.

Glass would make for a more durable layer of protection over a foldable screen, but is it even possible to make glass that folds this way?

There is a lot of science at play in making glass and its chemical makeup and forming process are what dictates the characteristics that the glass will have when competed. Glass can be dense, thin, thick, brittle, and even cloudy.

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Corning has a lot of experience with very thin glass. It has developed a solution about as thick as a human hair at 100 microns, which becomes flexible to a certain degree. Corning has been working with OEMs to develop prototypes for future folding devices and it plans to have some working glass designs in 12 to 18 months.

The challenge with glass in this application is that the folding form factor has a lot of variables (i.e. bending radius, impact resistance, and thickness) that need to be finalized so the glass can conform to this particular purpose. Since there is no standardized folding phone form factor, Corning needs time to figure out which compositions of glass will be the best for the application.

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Glass doesn’t break necessarily because its weak; glass breaks when stress is applied to a flaw or imperfection in the glass. Over time and use, the composition of Gorilla Glass deteriorates at a microscopic level, which explains why your phone may have survived the first eight drops but breaks on the ninth.

With every version of Gorilla Glass, drop resistance improves but scratch resistance eventually reaches a threshold. The density and thickness of glass can be altered, but hardness (resistance to scratching) is an integral property of glass. Drop resistance can be improved, however, by altering the makeup of the glass and parameters of the forming process.

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In the more recent years, Gorilla Glass was formed with curved edges to be used on phones like the Galaxy S7 edge and the OnePlus 7 Pro. This is something that could never be done with sapphire glass – which isn’t malleable the way Gorilla Glass is.

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Back in 2013, there was a sudden interest in sapphire glass for use in smartphone displays. It was a much harder material that was significantly more resistant to heavy scratching and it was once believed it would replace glass on most smartphone displays.

It didn’t exactly go that way. Sapphire glass turned out to be far more expensive to manufacture and its composition doesn’t allow it to be formed with curved edges.

Corning explains that sapphire glass finds great success in smaller formats like high-end watches. However, a larger piece of sapphire glass implemented for use in a smartphone display would make it more prone to shattering, since smartphones are subjected to tumbles and falls more so than, say, a wristwatch. Smartphone glass is under constant tension, thus not an ideal application for this kind of glass.

Wrap-up

We write about a lot of smartphones here at GSMArena, which means a lot of glass has passed through the office and we’ve touched a lot of it over the years. Though there are a few manufacturers that make glass for smartphones, Corning is the most popular brand found in over 7 billion consumer devices by over 45 major OEMs.

Smartphone glass is something that we don’t really think about – it’s virtually invisible. We sometimes only notice it when it gets scratched or cracks completely. Glass is an ideal material for these mini super-computers because it is durable and more scratch resistant than plastic.

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A shift happened in the last few years where OEMs decided to use glass on both sides of devices, thus making devices (arguably) more fragile than their metal-clad predecessors.

Though this may be one downside to using glass in smartphones, it’s a fully transparent material that allows light and radio signals to pass freely and without interference. Not only that, but it also allows for wireless charging while also being durable and attractive. It sure makes things easy for the manufacturer but what about the consumer? I’ll still argue OEMs should at least try to bring back smartphones with metal bodies, but maybe consumers are too deep into wireless charging these days.

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If you’re a clumsy person and your smart device’s glass somehow keeps surviving your drops, you have great luck. If that next drop takes the glass over the edge of its life, just recall all those times that the glass didn’t break.