> I was under the impression that 3M's main business is *manufacturing*
> plastics, not designing new ones.

It's both - if they didn't do the latter they would be no different to 
the other 10 million plastic manufacturing plants. If you've ever dealt 
with 3M (as a supplier for volume manufacturing) you would know they are 
not the cheapest, but they often have materials and technologies that 
nobody else has. This is their business model, it is not making 
bog-standard plastics cheaper than everyone else (they would never win 
this).

> (Actually, I was under the impression
> that 3M manufactures finished products that have plastic _in_ them, but
> I guess they probably sell raw plastic to other people...)

I don't think they do much of that, maybe for some specialised areas but 
I've never heard or seen anyone sourcing raw plastic from 3M.

> Really? I thought *all* transparent materials have an IOR different than
> air. As in, it's impossible to *avoid* this (e.g., if you wanted to make
> a kind of "invisible glass", you can't do it.)

You can create a cone structure on the surface of the material (with the 
points upwards so it's pointy to touch). Now so long as the size of the 
cones is smaller than the wavelength of light then you get a continuous 
smooth variation of IOR from the air to the solid. This prevents any 
reflections, so the glass looks invisible. I've seen prototypes of this 
and it really does look invisible (you can stick a patch of it on glass 
and it looks like someone cut a hole in the glass). The obvious problem 
with this is the tips of the cones wear off quite easily which starts to 
reduce the effect. Again, it's all about developing new materials and 
processes to achieve this kind of product.

There are other anti-reflection coatings already in use, with varying 
degrees of performance. One of them works by destructive interference 
and is used on glasses, outdoor displays etc, you can tell by the 
characteristic purple tint of the remaining reflection (it blocks green 
reflection mainly).

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