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Comment by Lramseyer | Hacker News Reader

This definitely looks like something that has the potential to be really useful, and gives the example of replacing gorilla glass. While I get that this is a very tough glass, I did not see anything about it's hardness in relation to gorilla glass, as hardness is the property that provides the scratch resistance that is so highly sought after in smartphone screens.

Toughness is how much energy a material can absorb, whereas hardness is the resistance to deformation. Think a rubber band vs. glass.

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According to wikipedia's AlON page it has a knoop hardness of ~1800 which from my understanding of things (I may have misread sources or be mistaken, I'm not a material scientist or even amateur) looks to be about equivalent to sapphire glass and much higher than gorilla glass (~600).

edit: in fact while I skipped the intro it states specifically that AlON has ~85% the hardness of sapphire, which more or less checks out. Suffice to say it has excellent hardness, way beyond gorilla glass.

I could find no data on relative permittivity though, and I assume that would be a factor for touchscreens.

I believe hardness is actually a bad thing in terms of replacing gorilla glass in phones. It increases the likelihood of shattering when dropped, and is the main reason for sapphire not being adopted.

> It increases the likelihood of shattering when dropped

AlON seems significantly tougher than glass as well as being way harder. So it looks to be both more scratch-resistant and more shatter-resistant.

> is the main reason for sapphire not being adopted.

Do you have sources (actual sources, not Corning fearing for their business) for that?

I'm no materials scientist. I just recall some articles I read when I was curious why I hadn't seen sapphire showing up in phone screens. Here is the first article Google pulls up.

http://time.com/3377972/why-apple-didnt-use-sapphire-iphone-...

I agree with you that AlON appears to be harder than glass. I just question if that is necessarily a good thing for consumer electronics. I expect we want something that is very tough but relatively flexible/soft.

> So it looks to be both more scratch-resistant and more shatter-resistant.

Refractive index 1.79, Abbe number 58… Why are my eyeglasses not made of this?

"main reason for sapphire not being adopted"

Edmund Optics sells a sapphire window thats unfortunately round, too thin (2mm) and too small (75 mm about 3 inches) to replace the glass in an iphone; the primary problem is that far too small optical window costs $650. On one hand a sheet large enough for a phone would cost more, on the other hand industrial production would be cheaper, much handwaving and it could be done but it'll cost $1K per phone, perhaps.

There have been phone screens made of sapphire, e.g. there was a special edition sapphire version of the HTC U Ultra (https://www.theverge.com/circuitbreaker/2017/5/4/15544426/ht...) which cost 150 Euro more than the glass version. I guess for just screen protection you don't need as high quality as for optical applications.

The Corning product is an extremely interesting material, the hardness varies with the depth leading to scratch resistance and a reasonably high level of resistance against shattering.

Is there are reason why artificial diamond coating hasn't taken off? Cost?

I wish it was possible to buy a phone with the option of a screen who’s glass was optimised for toughness rather than hardness, or at least an aftermarket replacement.

I can live with a screen protector, but broken glass is the bane!

I would assume "rugged(ized)" phone series have this sort of tradeoffs

I have a ruggedised case on my phone. Trade-offs hey.

Apple don’t make a ruggedised phone, if I wanted that I’d have to by an Android.

I would buy an Android, but I don’t want to.

Something like this https://www.catphones.com/ ?

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