The science behind Gorilla Glass 2

Donnell Walton is the manager of Corning’s Worldwide Applications Engineering division. SmartPlanet called him at his upstate New York office to learn more about Gorilla Glass 2, the 161-year-old company’s latest super-strong glass made for the displays of consumer electronics.

SmartPlanet: Last time we talked, Corning had just introduced the first version of Gorilla Glass. You told us that it was old science reborn into a new product.

DW: Yes, that’s right. Chemically-strengthenable glass has been around awhile. But being able to make that and align it with our current mode of making glass — specifically our fusion process for very high volume production — and optimize it for the current use case, that’s new.

As you can imagine, in the ’60s, when the precursor to Gorilla was developed, it was not for phones.

SP: And now it is.

DW: The way a [dropped] phone breaks — we have a lot of data on how that happens. The most common source of breakage for glass in a handheld device is “sharp impact damage” — you drop it flat on concrete or carpet, but if there’s something hard enough [on that surface] to pierce the glass, it will break it. The glass is going to shatter.

We see a lot of YouTube videos of people dropping phones on the sidewalk. It’s not the drop that does the damage, it’s the small rocks or debris on the ground that actually does it. We have some guys here who are experts in fractographic analysis, and they found that while a lot of times it looks like devices fail from the edge, it’s actually originating on the surface of the glass, near the edge.

People don’t upload videos of their phones dropping and not breaking.

SP: How do you approach making a successor to a product like this? If it’s half-century-old technology applied to a modern use case, where do you go from there?

DW: For the second one, we had more customer data. Everything at the Consumer Electronics Show this month was thinner and lighter.

From a materials standpoint, we could make the glass a little less susceptible to breakage — or, give it the same toughness but make it thinner and lighter.

The glass structure — it’s the same elements, by the way — was tweaked on a structural level to allow the chemical strengthening to be faster, to achieve a higher compressive stress. A lot of that was learned through Gorilla Glass 1.

SP: What are the tradeoffs of that kind of tweaking? In some kinds of glass, if you make it more resistant to one kind of stress, it becomes more brittle against another. It’s a zero-sum exercise.

DW: That’s right. There are a lot of strong materials in the world; there are a lot fewer transparent materials.

When you can tweak a glass or change a molecular structure, it amounts to a different glass. Its thermodynamic properties are different. It’s very easy to make something strong, but then it loses its transparency. It’s very easy for glass, as you change bond angles and inter-ionic distances, to become non-transparent or non-glassy.

The process of manufacturing is the same for both versions. From a scientific perspective and from a customer feedback perspective, we needed Gorilla Glass 1 and everything we understood there to make Gorilla Glass 2.

SP: Gorilla Glass was popularized in the consumer electronics industry, but it clearly has other use cases. Tell us about them.

DW: We’re starting to see glass used as a structural material, because it’s tough and light.

One of the devices that we had in our CES booth was the Hewlett-Packard Envy 14 laptop that had glass on the back, display, touchpad and palm rest. We also had an 82-inch touchscreen from Perceptive Pixel. We had reporters banging on it in the booth [to see how tough it was]. If you think about digital signage and public kiosks, you have no idea what’s going to happen out there.

We are also looking at adjacent markets — appliances, and also automotive, where thin and light is important, such as for sunroofs.

Also, architectural applications — in elevators, or for a building’s curtain wall. The same things that make the glass more impervious to sharp impact damage will also make it tough against blunt impact, such as a 65 mile-per-hour fastball — or hail — hitting a glass pane.

The use case for mobile [electronics] is a good one, but it’s a worst-case scenario. So we get ancillary benefits from that.

We want to make sure that we can make these huge pieces of glass. We want to move on [to manufacturing bigger panes] — like the Apple Store on Fifth Avenue [in New York City] moving to larger sheets of glass. Think about if you want to be on the front of a vending machine, or a refrigerator.

Plus, [device manufacturers] don’t just want to show off the glass, they want to interact with it. Going thinner is important for the sensitivity of these interactions. For capacitive touch applications, the closer the sensors are to your finger, the more sensitive it is. The thinner the glass is, the easier it is for sensors to detect that touch.

SP: Let’s talk about refrigerators for a moment. That’s a particularly interesting use case, because you introduce thermal concerns to the mix: the glass needs to insulate the food inside. We’ve seen transparent glass toasters, but they tend to be less effective than their metal counterparts. Is a transparent refrigerator technically possible?

DW: Could you have a transparent fridge door? Absolutely.

We’re also seeing people decorate the glass. On the Envy, there’s black ink on the back side of the glass, in a graphic design. The glass is like the ultimate clear-coat for that illustration.

We’re already seeing in some Asian markets glass as part of an appliance’s design language.

The fusion technology we’re using for Gorilla — we know how to make big glass. And that’s compatible with our existing way of making huge sheets of glass.

SP: You’ve only recently announced Gorilla Glass 2, but Gorilla Glass 3 is no doubt around the corner. Which prompts the question: where do you go from here?

DW: We’re going to continue to look at and listen to consumers.

SP: And what are they asking for? Thinner and lighter, sure. Perhaps more scratch resistance? I’m still not comfortable tossing my phone or tablet in the same pocket as my house keys.

DW: We’re still learning about it. If you have something that’s harder than glass, it’s going to scratch it. Hardwood floors are not harder than glass, most keys are not harder than glass.

But this compressive layer we put on there — it’s not the initial scratch that’s viewable, it’s the… the…

SP: …whispy hair-like thing?

DW: Yes! It’s that that light reflects off of and is viewable. We’re working on containing those. How do you make glass so that it’s hard to initiate that scratch? That’s a tough one.

Glass is harder to scratch than aluminum, magnesium — all these structural materials used on the back of your laptop that you don’t look at. How many scratches you have on the back of your laptop? It doesn’t matter. How many do you have on your display? That matters.