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Gorilla Glass

August 11, 2010

One of my mentors, Alten Gilleo,[1] an author of a highly-cited paper in the Physical Review,[2] had an interesting theory about new technologies. He believed that ideas were cyclic, their interest peaking at eight or ten year intervals. Eventually, at one of these peaks, particular ideas would attain special currency because of the business environment. At that point, much more research would be done, and new products would be introduced. I was reminded of this theory when I read about Gorilla Glass, a glass invented by Corning in 1962 that's only become important with the introduction of today's portable display devices.

Corning is famous for its Pyrex borosilicate glass, much beloved by chemists. Gorilla Glass is an aluminosilicate glass that's surface strengthened. A compressive stress induced at the surface make it resistant to fracture, a process that's done for many materials, including one that I co-developed.[3] Glass is typically surface-strengthened via an ion-exchange process that swaps larger-sized cations for smaller ones in the material. Corning's Gorilla Glass is a glass composition (in weight%. SiO2 61.91, Al2O3 17.43, MgO 3.26, CaO 0.15, TiO2 0.63, ZrO2 0.02, Na2O 12.58, K2O 3.45) that makes ion-exchange easier at lower temperatures.[4] This allows formation of a deeper compression layer while still maintaining good optical qualities. Since the base glass is much stronger than soda-lime glass, Gorilla Glass can have high strength in very thin sheets, and thin sheets are required for capacitive touch screens. The thin sheets are produced by a "fusion-draw" process in which molten glass flows down both sides of a suspended trough and coalesces at the bottom to form a flowing sheet of thin glass.[5]

Ternary Phase Diagram for a glass

Phase diagram from the Gorilla Glass Patent.[4] Phases shown are the equilibrium solids obtained after cooling from the melt. R2O is an alkali metal oxide (Li2O, Na2O, K2O).

It's been a long time from invention to a successful product for Gorilla Glass, which should serve as a warning to US corporations that research is a long-term investment. The following timeline was gleaned from the Corning web site:[6]
• 1960 - Corning launches Project Muscle to find a glass as strong as steel.
• 1961 - Project Muscle experiments lead to an ultra strong glass named Chemcor.
• 1962 - Corning sends a film clip of scientists banging and bending Chemcor glass to 200 television stations.
• 1963 - Corning receives nearly 2,000 inquiries on Chemcor glass, including use for telephone booths. The material, however, is too expensive for telephone booths. Only a few of those ideas made it into production, and none of them became a major product line.
• 1964 - The Chemcor process is patented by Corning, and it's introduced into automotive, aerospace and pharmaceutical products.
• 1965 - Chemcor glass was used in such products until the 1990's, and Chemcor variants continued in ophthalmic and pharmaceutical products.
• 2005 - The first mobile device to incorporate cover glass appeared, and Corning started looking for Gorilla Glass insertion into display products.
• 2007 - Corning's Gorilla team optimized the glass composition, and Gorilla Glass for display covers was put into production.
• 2008 - Continued development allowed the glass to be produced in uniform, thin sheets with a pristine surface.
• 2010 - Gorilla Glass is now in more than 19 brands, including LG, Samsung, Motion Computing and Dell, and in more than 100 devices. Although Corning can't admit that Gorilla Glass is used on Apple products, it's apparently used in the iPhone 4.[7]

Display electronics have been very good to Corning. The glass used for liquid crystal displays comprised most of Corning's 2009 revenues of $5.4 billion.[5] Gorilla Glass contributed $170 million in revenues in 2008.[5] Of course, the larger the display, the better the sale price, so Corning has been promoting the idea of thin, frameless television displays that hang on the wall like a picture. This sounds like the science fiction I used to read as a child.

An interesting postscript to all this is the fact that most of Gorilla Glass manufacturing will be outsourced by Corning to Asia. Production will be expanded at the Corning facility in Harrodsburg, Kentucky, where all Gorilla Glass is presently manufactured; but the display manufacturers are all in Asia, so Corning will supply them close to home.[8] There are 300 employees at the Harrodsburg facility, and Corning is expected to add about eighty more. At the same time, it's building a plant at Shizuoka, Japan, that will employ about the same number, and it may build other facilities in Asia.[8] Will the exodus of manufacturing jobs from the US ever cease?


  1. J. J. Barrett and D. M. Gualtieri, "Obituary: M. A. Gilleo," Physics Today, vol. 34, no. 7, July, 1981, pp. 74f.
  2. M. A. Gilleo and S. Geller, "Magnetic and Crystallographic Properties of Substituted Yttrium-Iron Garnet, 3Y2O3·xM2O3·(5-x)Fe2O3," Phys. Rev., vol. 110, pp. 73-78 (1958).
  3. Robert C. Morris, Devlin M. Gualtieri, Dave Narasimhan, Philip J. Whalen, "Epitaxially strengthened single crystal aluminum garnet reinforcement fibers," U.S. Patent No. 5,572,725 (Nov 5, 1996).
  4. David C. Boyd, "Sodium Aluminosilicate Glass Article Strengthened by a Surface Compressive Stress Layer," U.S. Patent No. 3,778,335 (December 11, 1973).
  5. Ben Dobbin, "1962 glass could be Corning's next bonanza seller," Google News (August 1, 2010).
  6. Corning Gorilla Glass Timeline on Coning Web Site
  7. Apple iPhone 4 Retina Display Protected by Corning Gorilla Glass (intomobile.com)
  8. Laurent Belsie, "Gorilla glass invented in US. But will jobs head to Asia?" Christian Science Monitor (August 2, 2010).
  9. Corning Gorilla Glass demonstration video (YouTube).
  10. "Glass once used in windshields and space crafts reborn into cell phones and electronics," Corning Web Site.
  11. Specifications of Gorilla Glass.                                   

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Linked Keywords: Physical Review; Corning; Pyrex; borosilicate glass; aluminosilicate glass; compressive stress; fracture; ion-exchange process; soda-lime glass; capacitive touch screens; liquid crystal displays; outsourced; Harrodsburg, Kentucky; Shizuoka, Japan.

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