You might remember that, back in November, Apple(s aapl) and GT Advanced Technology signed a five-year, $578 million deal for sapphire manufacturing. That’s a lot of glass, and a new patent published today details methods in which it might be put to use, reports Apple Insider.
The patent – Attachment Techniques – starts off by explaining the difficulty in attaching sapphire to other materials.
“Sapphire, for example, may be particularly difficult to mechanically couple with other materials. Specifically, machining sapphire may be difficult due to its crystalline structure, hardness and strength. Further, sapphire may have a high level of stiffness relative to other materials, as well as a relatively low level of thermal expansion. As such, conventional adhesive attachment techniques may not be effective or lasting. That is, mechanical strain on the adhesive bond resulting from the difference in the thermal expansion and stiffness of the materials eventually causes failure of the bond.”
To work around this, one of the methods Apple describes involves creating an aperture within a sapphire substrate, filling the aperture with an attachment material (something with a lower melting point, like metal or plastic), and mechanically joining that with another part using the attachment material.
In the image below, Apple suggests this technique can be used to create “a sapphire sheet, a sapphire sheet with a glass laminate layer, a plastic, or other suitable material, through which a visual output of the device 100 is output.”
Apple already uses sapphire glass for protect the camera sensors on its mobile devices, as well as for the Touch ID-powered Home button on the iPhone 5s. The technique described here shows how Apple could use a full sheet of sapphire on the front and back of the iPhone, as opposed to Corning’s Gorilla Glass(s glw).
Why would Apple want to replace Gorilla Glass? “Chemically strengthened glass can be excellent, but sapphire is better in terms of hardness, strength, and toughness,” Matthew Hall, Director of the Center for Advanced Ceramic Technology at the Kazuo Inamori School of Engineering at Alfred University, said in an interview with TechCrunch.
Then again, Corning has plenty of information (and video) to suggest otherwise. Ultimately, this is just a patent, and not necessarily indicative of whether Apple has plans to make a bigger switch to sapphire or not. At the end of the day, it could just be planning to crank out a heck of a lot more sapphire home buttons.