Sapphire screens - the gem of the mobile world?

26th Feb 2014 | 18:45

Sapphire screens - the gem of the mobile world?

Making the iPhone even more precious

There's been a lot of talk surrounding sapphire screens for smartphones recently, and it's one of the heavily rumoured features for the upcoming iPhone 6.

Apple has even gone and purchased a sapphire product company, fuelling the rumours of an iPhone 6 appearance further and it could be the catalyst the screen tech needs to catapult it into the mobile mainstream.

So why is it so important? We're here to set the story straight about what sapphire screens are and why we should all be excited for the mobile future.

What exactly is sapphire?

We all know what sapphire is, right? It's that beautiful blue gemstone found on the ring given by Prince William to Kate Middleton for their engagement in 2010.

So why is this precious gem being constantly bandied about as the future of smartphone screens?

In fact sapphire is much more than a gemstone, it is a crystallized form of aluminium oxide which sports a natural blue hue thanks to traces of elements such as iron and titanium.

Why is it good for phones?

Manufactured sapphire has been around for a while and it's used on all of Tag Heuer's watches, as well as being the transparent armour that is currently found on military vehicles and there is some pretty sound reasoning behind this.

It is common knowledge that there is little in the universe that is harder than diamond, a substance that measures 10 on the Mohs mineral hardness scale.

The Mohs scale measures how easily different minerals scratch from 1 to 10, 1 being the softest and 10 being the hardest.

Smashed iPhone

Sapphire measures nine on that scale, only one less than diamond and two to three higher than ordinary glass.

Putting this into context, sapphire mobile screens should be far more scratch and crack resistant than a traditional chemically strengthened glass screen.

Whilst we highly doubt your next phone will be bullet proof like the M142 High Mobility Artillery Rocket Launcher's windscreen, we could be looking at mobile screens that won't crack if dropped, nor scratch if left in a handbag or pocket with a set of keys.

Hasn't sapphire been used before?

With all recent the talk of sapphire screens you'd be forgiven for thinking that its use in the mobile world is something that is completely new.

Anybody with an iPhone 5 or 5S will know (possibly) that's not the case.

iPhone 5S Touch ID

Apple in particular has been using sapphire for a while, with it covering the Touch ID fingerprint sensor on the 5S and the camera lenses of both devices.

What about Gorilla Glass?

The use of sapphire in mobile screens places a lot of pressure on the current screen manufacturers, none more so than Corning who produces Gorilla Glass.

It's the screen tech that is currently found on a lot of the high end flagships including the HTC One, Samsung Galaxy S4, LG G2 and Nokia Lumia 1520.

Figures from Corning's news centre suggest Gorilla Glass is currently found in over 1.5 billion devices, a number that is certainly not to be baulked at.

Gorilla Glass

The same site also show that sapphire is actually harder to scratch than Gorilla Glass, something that is reiterated by Matthew Hall, Director of the Center for Advanced Ceramic Technology at Alfred University's Kazuo Inamori School of Engineering.

"Chemically strengthened glass can be excellent, but sapphire is better in terms of hardness, strength, and toughness" Hall explained, adding "the fracture toughness of sapphire should be around four times greater than Gorilla Glass – about 3 MPa-m0.5 versus 0.7 MPa-m0.5, respectively."

This comes with some rather large downsides though. Sapphire is both heavier at 3.98g per cubic cm (compared to the 2.54g of Gorilla Glass) as well as refracting light slightly more.

This means that under the same lighting conditions sapphire screens will seem darker.

Gorilla Glass has one more massive trick up its sleeve; its manufacturability. Hall admits that he is less "less familiar with the details of sapphire production, but it's my understanding that all methods are batch-based while the relevant glass making process is continuous in nature."

This means sapphire screens will be more expensive to produce, with analysts currently claiming that Gorilla Glass is approximately 10% of the price ($3 rather than $30).

So my iPhone will get more expensive?

The reasonable assumption then is a sapphire screen will make your next iPhone more expensive, unless Apple finds a way to either absorb the cost or manufacture enough to scale down costs.

It might have just been able to do that following a deal with GT Advanced, a company that has developed a method for creating a sapphire sheet that is thinner than a human hair and can be mounted to a glass display.

This method makes production of sapphire screens significantly cheaper.

The deal worth $578 million in prepayments has also allowed GT to purchase nearly 1000 furnaces to help produce the sapphire screens thereby allowing economies of scale to reduce the costs even further.

Are there any problems?

All the work that Apple is doing with GT Advanced should see it overcome the largest problem that faces any potential sapphire screens, but that doesn't mean other problems won't arise.

A big problem that has faced sapphire to date is the purple flare that surrounded areas of bright light on the iPhone 5's camera.

This purple fringe was attributed to the sapphire lens, although was likely caused by chromatic aberration (a light distortion that can be tricky to correct on large lenses, let alone those found on smartphones).

Another key problem that any potential iPhone with sapphire screen will face is one that we have already touched upon, screen brightness.

If you've shelled out for a new iPhone you're going to be pretty miffed if you can't use it outside.

This is something that is likely to be significantly reduced with thinner sapphire screens mounted to glass, but can also be remedied with brighter screen technologies such as AMOLED displays.

Put everything together and we're left salivating. Can you imagine a 5-inch sapphire AMOLED iPhone 6? We can but dream.

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