What does the extremely fragile glass do in Kindle3's pearl e-ink display?

Question

I've recently seen two great tutorials that disassemble the Kindle 3 for repairing. One is this great Fix your broken Kindle Keyboard Screen tutorial by ghwhitcher, and the other is the Amazon Kindle 3 Take-apart Guide by Powerbook Medic.

Both warn that on the display's back there is an extremely fragile layer of glass. ghwhitcher says that it is only kept unbroken for normal operation because the kindle3's case is strong enough to protect it to some degree. He actually broke it first, even with being careful I suppose, when disassembling—he warns.

My question is, what does this glass do? I mean, why does it screw the entire display part if it gets broken? What is this glass' function as part of the screen module?

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illustration taken from the tutorial:

Answer 1

E-ink displays have to be mounted on a surface. In this case I assume that was done on the glass. This keeps the E-ink nice and flat (good for equal visibility of all pixels) and for extra reflectiveness of ambient light, if the glass is part of a mirror (as it seems to be).

The display is actually a thin film transistor array and my guess is that if the supporting glass breaks, some of the circuitry of the thin film get ripped. A single rip across the width or height would make addressing the film as an array impossible.