Apple has patents for a sapphire-glass blend screen that could explain why sandpaper can scratch a supposed leaked iPhone 6 screen, the Guardian has established.
A new video that apparently shows a 4.7in sapphire screen from an iPhone 6 being scratched by sandpaper could “certainly” be a legitimate blend of sapphire and glass, according to Prof Neil Alford of the department of materials at Imperial College London, who was consulted by Apple about sapphire screens 18 months ago.
“Apple has patents for both sapphire lamination – taking two different cuts of sapphire to induce strain and increase its resilience – and for fusing quartz or silica (glass) to sapphire,” Alford explained to the Guardian. “So they could certainly do that.”
From lens to screen
Apple currently uses sapphire crystal for its camera lenses and the cover of the iPhone 5S's Touch ID fingerprint sensor, but the super-hard material could make excellent screens that are much more scratch resistant than traditional glass and potentially even Corning’s Gorilla Glass, which covers the majority of smartphone and tablet screens.
Apple has entered into a joint venture in the US with GT Advanced to build plants and furnaces able to produce sapphire in industrial quantities for a "critical component" that it said in trade documents would be shipped abroad for assembly. That could refer to the touch sensors – or to screens.
The new video shows Marques Brownlee scratch both an iPhone 5S screen – which uses the third generation of Gorilla Glass – and the alleged iPhone 6 4.7in screen with two different types of sandpaper.
A softer garnet sandpaper, which is about six on the Mohr scale, and emery, which is about eight on the Mohr scale, were used on the two screens.
“The Mohr scale is a relative scale used by geologists and mineralogists to describe minerals and goes from one, which is super soft, to 10, which is super hard,” explained Alford. “The softest mineral on the scale is talc rising to quartz at number seven and diamond is 10. Corundum, which is sapphire, is number nine.”
“The relative hardness of sapphire is 400, compared to quartz which is 100, so it is a lot harder than quartz,” Alford stressed.
Quartz is a crystal formed from silicon dioxide, the main component of glass and sand, and is used in electronic components including digital watches as part of the time keeping mechanism.
‘Smash the thing up, stick it under a microscope’
In the video, Brownlee manages to scratch both iPhone screens with the sandpaper, with the alleged iPhone 6 screen showing higher resistance to scratching with the garnet and emery sandpapers than the iPhone 5S Gorilla Glass screen. The sapphire home button of the iPhone 5S resisted all scratches from both sandpapers.
Brownlee concludes that the leaked iPhone 6 screen could be a blend of sapphire crystal and traditional glass, which Alford agrees is possible.
“I would smash the thing up, stick it under a microscope and you’d have your answer as to whether this is aluminium oxide (sapphire) or silicon dioxide (glass),” said Alford. “You can’t truly tell until you get it under a microscope.”
Sapphire crystals are made from aluminium oxide powder, compared to silicon dioxide in standard glass. Once heated and cooled, it can be cut and formed into glass-like layers – known as sapphire glass. The optically transparent material has long been used for camera lenses as well as the screens of high-end watches because of its combination of scratch resistance and high transparency.
Sapphire has many advantages over glass, but has been prohibitively expensive to produce in large areas despite abundant raw materials. Creating artificial sapphire is not a problem in smaller areas for electronics and other uses, much in the same way artificial diamonds are used in manufacturing.