The iPhone 6 will be the most radical redesign in iPhone history. Central to that will be the move to larger 4.7-inch and 5.5-inch displays and central to convincing us this is a good idea will be Apple’s use of sapphire displays. But what is a sapphire display? Why is it better than glass and will it cost the earth?
Much has been written – a lot erroneously – about all these elements, so I sat down with Professor Neil Alford, head of the Department of Materials at Imperial College London. Professor Alford was directly consulted by Apple 18 months ago about using different materials (including sapphire) in future devices. So let’s separate fact from fiction:
Tell me about your consultancy work with Apple?
“We chatted about the external side of iPhones and iPads including aluminium cases and the screen. Specifically we talked about alternatives for glass and my suggestion was sapphire because if its scratch resistance and wide use.”
What Is Sapphire? Is it Just Like The Gemstone?
“It is the same chemical compound as the sapphire jewel, aluminium oxide, and sapphire is the single crystal form of it [the scientific name is ‘corundum’]. The difference with [sapphire used in gadgets] is it is artificially made, unlike sapphire gemstones which typically come from raw materials. When natural sapphire is hewn from rock its blue colour is actually from impurities. Pure sapphire is actually completely clear.”
Note: Sapphires can also be yellow, purple, orange or green – different compositionally from emeralds – while red aluminium oxide is a ruby.
Why Is It So Useful
“It is very hard. On the Mohs scale of mineral hardness corundum is a 9 and the scale runs from 1 to 10. 1 is talc, quartz [the core mineral in glass] is 7, corundum is 9 and diamond is hardest at 10 (full table below).”
A recent video (below) showed an alleged iPhone 6 sapphire screen could bend. Why?
“If sapphire is flaw free it can do that. This isn’t unique to aluminium oxide. [Glass] Optic fibre can be twisted around a finger when it is fortified. It is all to do with strength.”
But sapphire glass is intrinsically stronger than glass?
“It is not so simple. It depends on purity and whether it is combined with other elements to save cost. Glass variants can be extremely tough and they continue to make advances. Corning [maker of Gorilla Glass, used in most smartphones including the iPhone 5S] said it isn’t worried yet.”
Note: Corning Gorilla glass is chemically toughed by ion exchange which swaps sodium ions in the glass surface for potassium ions (which are 30% larger) and uses thermal tempering which cools layers of the glass differently.
Is this because sapphire glass is far more expensive?
“Not necessarily. The process for making sapphire is more expensive because the material has to be melted at a much higher temperature (2027 degrees C / 3761 degrees F) than Quartz (1670 degrees C / 3038 degrees F). For glass you just chuck it onto a tin and it comes out flat, there is no worrying about crystallising. When making sapphire the purity has to be pretty high and it is tougher to crystallise [key to strength and transparency].
But if you can do this process on an economy of scale then the costs [of making sapphire] can be competitive. It is actually a commodity material. When people think of blue gemstones and natural sapphire that is rare, but commercial artificially made sapphire is not.”
What unknowns remain about the iPhone 6 sapphire display?
“Whether there are different grades. Apple has a lot of smart patents including sandwiches of glass with sapphire so it might be going down that route. The only way to tell exactly would be to smash it up and put it under my microscope. Then I could tell you.”
Will Apple have a monopoly on sapphire screens?
“There are a lot of smart guys at Apple and as I mentioned it has some good patents, a lot of variations, but you can’t stop others using it. Sapphire has been used for a long time in other sectors and even some phones. [Ex Nokia luxury brand] Vertu has used sapphire for a long time so it won’t be exclusive, but the supply chain is key.”
Note: Apple signed a deal with GT Advanced Technologies in November 2013 to manufacture sapphire crystals at a new plant in Arizona allowing it to produce sapphire rather than having to source it.
All of which potentially gives Apple a first mover advantage, but rivals have not been sitting still. Professor Alford points out Kyocera has synthesized sapphire for over 41 years for everything from electronics and LED lighting to watches and camera lenses. It also recently showed off its first sapphire phone screen, even going so far as to poke fun at Apple in the process.
As such the rush to produce smartphones with sapphire displays is well under way, but it remains far from a one horse race.
My thanks to Professor Neil Alford for his time.
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