Making Unbreakable GlassBy
In January 2007, Steve Jobs had a problem. The device he showed the audience at the historic iPhone debut had scratches on its plastic screen because he had been carrying it around in his pocket. He ordered his team to get a glass cover for the display that wouldn’t scratch or crack. In the five months before the final release, Apple came up with a solution that quietly altered the course of mobile computing.
In a curious crossing of paths, Jobs went to Corning Glass in upstate New York—the same place Thomas Edison had taken his experimental light bulb—to find a clear cover for the device. Both iconic inventions depended on a glass solution without which they couldn’t succeed. On June 18, 2007, an Apple press release announced the availability of the first iPhone, and the subtitle of the release boasted: “Now Features Durable Glass Top Surface.”
GORILLA GLASS IS BORN
The glass Corning provided Apple had been developed in 1960. It was called Chemcor and was named after the chemical strengthening process that produced it. It was much stronger than ordinary glass and was produced for use in automobiles, eyeglasses, and phone booths. The product was only modestly successful before Jobs decided his company would need millions of square feet of the glass in ultrathin sheets. Corning renamed the material Gorilla Glass, and, today, a little more than 13 years later, it has become a part of 8 billion mobile devices from more than 45 major brands.
With Chemcor, Corning discovered you can make even very thin glass sheets harder through tempering. By quenching the heated glass, the outer surface cools and contracts more quickly than the center, and as the exterior compresses, the interior retains tension as it pulls against the hardening surface. Gorilla Glass added a chemical tempering to this process with an ion exchange that changes the composition of the surface. The glass is immersed in a salt bath at 752°F (400°C), and the heated solution forces the smaller sodium ions to escape the glass surface and larger potassium ions from the solution are drawn into their place. As the surface cools, the larger ions diffuse into the surface, and the contraction creates a layer of compression that makes the glass very resistant to breaks and damage such as cracks and scratches.
Corning explains that the hardness and scratch-resistance of Gorilla Glass can be measured on the Mohs scale of mineral hardness. The scale uses the ability of minerals to scratch to get a number from one to 10 to measure relative strengths. For example, as the softest mineral, talc is rated 1 because it’s easily scratched with a fingernail. The hardest, at 10, is diamond, which can only be scratched by another diamond. Ordinary glass comes in at a softer 7. After undergoing Corning’s heated salt bath, the sixth-generation version of Gorilla Glass is only one number down from diamonds with a rating of 9.
It’s great engineering, but there’s a catch. The closer you get to diamond-hard compactness, the more difficult it is to work with the material. Corning delivers Gorilla Glass in sheets, and it’s up to Apple and other clients to cut, shape, and drill the glass for their devices. For this, you need diamond-tipped saws, drills, and contour tools. A special manufactured abrasive, cubic boron nitride (CBN), can also be used.
GEN 7 VICTUS
On July 23, 2020, Gorilla Glass got a new name and the world got an improved generation seven of the 13-year-old wonder glass. Corning renamed it Gorilla Glass Victus, and it was introduced as “the toughest Gorilla Glass yet for mobile consumer electronics.”
Corning concentrated in recent years on the ability of Gorilla Glass to survive drops. It did this because, “Dropped phones can result in broken phones, but as we developed better glasses, phones survived more drops but also showed more visible scratches, which can impact the usability of a device,” said John Bayne, senior vice president and general manager of Corning’s Mobile Consumer Electronics. “Instead of our historic approach of asking our technologists to focus on a single goal, we asked them to focus on improving both drop and scratch, and they delivered Gorilla Glass Victus.” Victus has improved drop performance, enabling phone glass to survive intact when dropped onto rough concrete from up to two meters high, and now it’s twice as scratch-resistant as the sixth generation.
And so the partner of Edison and Jobs continues on today, often transparently, creating an impressive variety of construction materials for use in buildings, lenses for telescopes, fiber transmission materials, heads-up displays for fighter jets, watch crystals, and more. The next challenge for Bayne’s Mobile Consumer Electronics division is a glass that can handle extreme bending for the new folding phones.
Photo courtesy of Corning Incorporated