How Gorilla touchscreen glass works in smartphone

Introduction

Laymen explanation

As we carry around computers, tablets, smartphones, MP3 players and other devices, we risk damaging them through everyday use. Corning's Gorilla Glass stands up to abuse with scratch- and impact-resistant qualities. And Corning's approach allows the glass to be incredibly thin, meaning it won't interfere with touch screens or add significant weight to a device.

What's so special about Gorilla Glass that sets it apart from other kinds of glass? The answer involves incredible temperatures, a special trough, robots and a molten salt bath. The finished product is a thin piece of glass that can withstand a lot of punishment.

Technical explanation

While you might think of glass in its manufactured form, the truth is it's a material we find in nature. Certain rocks and minerals become glass after coming into contact with high temperatures. This occurs naturally along lava flows and places where lightning has hit the ground.

To manufacture Gorilla glass, Corning takes the silicon dioxide (SiO2) and combines it with other chemicals before melting it down into a glass melt. The resulting glass isaluminosilicate -- that means the glass contains aluminum, silicon and oxygen. The glass also contains sodium (Na) ions, which become important in the next phase of manufacturing.

Corning pours the molten glass into a V-shaped trough but doesn't stop at filling the trough to the top. The company continues to add molten glass until the glass begins to overflow the sides of the trough. Automated robotic arms draw the sheets of glass from the edge of the trough. Each sheet is just over half a millimeter thick. If you were to use this glass for a screen on your electronic devices, you'd end up with a very clear covering. But it's not damage-resistant like Gorilla Glass -- it's just aluminosilicate glass. To give Gorilla Glass its ability to withstand scratches and cracks, Corning gives these sheets of glass a little bath.

The real secret behind Gorilla Glass involves a chemical process called an ion exchange.The aluminosilicate glass from the first phase of the manufacturing process contains sodium ions. Corning dips these sheets of glass into a bath of potassium ions.

Sodium is higher on the periodic table than potassium, which means an atom of sodium is smaller than an atom of potassium. You might think that at the atomic scale size doesn't matter but it turns out that's not the case! If you could take the sodium ions out of the aluminosilicate glass and replace them with larger potassium ions, the sheet of glass would experience compression.

Imagine you have a net. The line in the net is flexible but taut -- there's not a lot of give. In each hole of the net there's a golf ball held into place. Now imagine that you replace all the golf balls with baseballs. That's similar to what's happening on an atomic level with an ion exchange.

So how does it work? To replace sodium with potassium, you first must break the ionic bond sodium has with the glass. That's why the potassium salt bath is so hot -- Corning says the bath reaches a temperature of 400 degrees Celsius (752 degrees Fahrenheit). At this temperature, the energy (heat) breaks down sodium's ionic bond to the aluminosilicate. But one of the qualities lower active metals have is that they can maintain an ionic bond at higher temperatures than the lighter active metals. Potassium weighs more than sodium -- that 400 degrees Celsius (752 degrees Fahrenheit) isn't enough to keep potassium ions and the aluminosilicate apart.

After a nice hot dip in the potassium bath, the aluminosilicate emerges compressed by potassium ions. The compression creates a protective layer on the glass and gives it strength that normal glass doesn't have. And the environmentally conscious can rest easy -- Gorilla Glass is recyclable.

Market penetration method

The ion exchange process isn't new and Corning's Gorilla Glass isn't the only chemically strengthened glass on the market. But Corning has demonstrated the strength of its glass in venues like the Consumer Electronics Show where the company invited people to test come up and see how much pressure it would take to break a piece of its glass. Untreated glass would break relatively easily. Standard chemically strengthened glass would put up more resistance but would also break given enough pressure. Gorilla Glass was much more resistant to damage.

How does Gorilla Glass get into products? Corning partners with manufacturers and provides Gorilla Glass as part of the product's manufacturing process. The average consumer can't go out and buy a sheet of Gorilla Glass to fit on top of an existing device. In that sense, Corning is an original equipment manufacturer (OEM). The finished product will contain Corning's glass but the finished product will have another company's brand on it. Its product demo is at http://www.corninggorillaglass.com/en/videos/85

Competitive product

Dragontrail, manufactured by Asahi Glass Co., is an alkali-aluminosilicate sheet glass engineered for a combination of thinness, lightness and damage-resistance, similar to Corning'sGorilla Glass.

Reference

https://www.corning.com/in/en.html

http://electronics.howstuffworks.com/everyday-tech/gorilla-glass.htm

https://en.wikipedia.org/wiki/Dragontrail