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Corning says Gorilla Glass trumps sapphire screens, but the truth is more nuanced

John P. Mello Jr. | May 27, 2013
Corning claims Gorilla Glass is a better, more durable display material than sapphire—but is it true?

Corning and Gorilla Glass

Corning has begun a pre-emptive strike against a competitor to Gorilla Glass, its product widely used in the displays of many smartphones.

The company has posted an article to the Web previewing the next generation of its product, as well as a stress-test video.

In its article, Corning maintained that Gorilla Glass has a number of benefits over sapphire as the cover glass for mobile devices, such as smartphones. It asserts that Gorilla Glass is lighter than sapphire; consumes less energy and costs less to produce; is brighter; is thinner so it can be curved and more responsive to touch; and is stronger.

In a stress test, Corning shows a smartphone-sized, 1mm thick sheet of sapphire breaking after 161 pounds of pressure is applied to it, while the Gorilla Glass remains unbroken after 436 pound of pressure is applied to it.

"Discussion seems to center around sapphire as an obvious solution for a cover material," Corning Senior Vice President Jeffrey W. Evenson explained in the company's article.

"What would people say if someone invented a cover that was about half the weight, used 99 percent less energy to make, provided brighter displays, and cost less than a tenth of sapphire?" he asked. "I think they'd say that sapphire was in real trouble."

"It so happens that we at Corning already invented that cover—and it's called Gorilla Glass," he said.

Immunity to scratching
While Corning's test suggests that Gorilla Glass may be more resistant to sheer pressure, the claims don't address a major draw for sapphire screens. One of the applications for sapphire has been in high-end watches because it's immune to scratching. Only diamond or other sapphire can scratch sapphire.

Corning does have something to say about those watches, however.

"Those covers are much smaller than a mobile phone and are two to three times thicker than Gorilla Glass," James R. Steiner, senior vice president and general manager of Corning's Specialty Materials segment, said in the Corning article.

Sapphire's immunity to scratching is also the reason Apple uses it to protect the iPhone 5's camera lens, and may use it to protect the rumored fingerprint reader in the next version of its smartphone.

While Gorilla Glass has a broad appeal—it's in 1.5 billion consumer electronic devices, according to Corning--sapphire has largely been used in specialty applications: a component in LEDs, sensor windows in aircraft, and military uses.

Sapphire strikes back
The barrier to sapphire being used as a smartphone cover isn't strength, but cost, noted Jeff Nestel-Patt, director of marketing for GT Advanced Technology, a maker of sapphire.


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