TechTheDay

Rumors have been spreading that Apple is planning to use sapphire on their latest flagship device, the iPhone 6. One rumor is even claiming that the newest Apple smartphone is up for a fall release—with a sapphire glass covering its display. Is a sapphire glass iPhone a representation of what should be the future of mobile displays? What are the pros and cons of using this type of glass or crystal over displays?

The sapphire that will allegedly be used on the iPhone 6 is synthetic sapphire. It is produced from agglomerated aluminium oxide heated (without melting) and fused in an inert atmosphere. Of course, unlike naturally occurring sapphire, the result of this industrial process will be a transparent polycrystalline material fit to be used as a glass covering for mobile displays.

Advantageous Characteristics of Sapphire

Basically, two characteristics make sapphire a very good material for mobile displays. These are its hardness and transparency.

Hardness

Next only to diamonds, sapphire is the second hardest material in the world. In natural existence, it is a gemstone variety of the mineral corundum with the chemical name aluminium oxide. It scores 9 on the Mohs scale, only a point lower than diamond’s 10. That said, sapphire’s main advantage is its extraordinary hardness, making it a great option for covering displays.

This hardness leads to sapphire glass being virtually scratch resistant. In theory, only materials with a Mohs scale rating of 9 or higher can scratch it. Knives, keys, and the metallic edges of other gadgets can’t scratch sapphire glass. There are tempered glass products that boast similar scratch-resistance but they are nowhere near the durability of sapphire.

If used on mobile device displays, the instances of cracking or shattered screens can be significantly reduced. Of course, sapphire is not indestructible. It is still a crystal, after all. It will still crack when a considerable amount of pressure is applied to it.

Transparency

Sapphire also comes with an excellent level of transparency or the ability to let light pass through it. It is transparent for light with the wavelength range of 150 nm to 5,500 nm. This means that it can let through even invisible light (UV and IR) or those that cannot be seen by the human eye. Humans are only capable of perceiving light at the 380 nm – 750 nm wavelengths.

Disadvantages

Expectedly, folks at Corning, the manufacturer of the Gorilla Glass used by almost every mobile device that touts scratch resistance, are not delighted by the idea of replacing their product with sapphire glass. Morgan Stanley, a Corning SVP, is of course not inclined to supporting the use of sapphire glass on displays.

The corning executive lists a number of disadvantages in sapphire that make it less desirable in comparison to Corning’s Gorilla Glass. The supposed disadvantages are as follows:

1. Sapphire is 10x more expensive than Gorilla Glass. It will obviously raise the prices of mobile devices.
2. It is not environmentally friendly since it takes about 100x more energy to produce sapphire glass when compared to the amount of power necessary in creating Gorilla Glass.
3. Sapphire is less transparent, which can mean dimmer displays or shorter battery life.
4. Sapphire glass is not completely unbreakable. While it may be more scratch resistant than Gorilla Glass, it is not as capable in receiving pressure compared to Corning’s glass. Gorilla Glass is said to be able to take around 2.5x more pressure than Sapphire, based on Corning’s tests.

Answering Morgan Stanley’s List of Disadvantages

The four supposed disadvantages are only assertions of Morgan Stanley. While numbers 1 and 2 are absolutely valid, numbers 3 and 4 are refutable.

On the issue of sapphire’s transparency (number 3), Apple’s use of sapphire glass to protect their camera’s lenses proves that light transmission is not an issue. iPhones don’t produce dim photos. They even output brighter and clearer photos compared to other high end devices. What matters is that sapphire can let all visible light through it or light with the wavelength range of 380 nm – 750 nm.

With the issue of sapphire’s breakability, it can’t really be considered a disadvantage. The fact is that it is considerably stronger than durable tempered glass like Corning’s Gorilla Glass. The 2.5x pressure capacity Corning seems to be boasting is the ability of Gorilla Glass to withstand pressure if it is allowed to flex. The glass covers used on mobile devices are not designed to flex to absorb pressure.

The Bottom Line

In sum, sapphire is indeed physically superior compared to Gorilla Glass or other tempered glass products like DragonTrail from Asahi. In practical terms, however, the tempered glass used on most mobile devices at present is still better. This is because of the cost advantage and the lower amount of energy required in manufacturing durable tempered glass.

Unless sapphire glass production becomes dramatically more efficient and unless it becomes considerably less expensive, it cannot put Gorilla Glass and other similar durable glass products out of business. The future of mobile displays should be about overall efficiency, cost-effectiveness, and functionality. Bumping up durability and scratch resistance is just like increasing pixel counts in cameras and displays. It’s a costly and not-so-significant reason to upgrade.