Samuel M. Goldwasser wrote:
This is strange.

I have an LCD optical polarization rotator. It's basically a single
pixel panel a bit less than 1 cm square. It rotates the optical
polarization of a laser when driven with a TTL squarewave.

Those details are not important though.

The bare glass panel was dropped. And when retrieved with NO visible
damage - no cracks or breaks in the sealing - a small blemish could be seen
about 1/3rd of the way in from one side. This was not near any seam
and there was no evidence of any crack. What's more, the blemish -
which had the appearance of an irregular bubble - could be pushed
over to one edge by gently massaging the glass panel,
where it spread out but happily remained at the edge,
with apparently no effect on the performance of the device.

So, where did it come from? Is it actually an area of vacuum that
formed when the LCD material was pulled away from the glass?

Just curious.

I have been lucky making lcd glasses to switch between transparent
and milky vision.
The sides of an lcd are sealed with glue, we used 5 minute 2 component
epoxy.
When you have a bad seal, any mechanical violence can draw some air
between the glass layers.
The bubble is not harmful, but lcd fluid can leak out, and contamination
can get in.
That IS harmful to the lcd, the contamination together with water from
the atmosphere will react with the applied voltage, and starts degrading
the area around the leak.
Its a slow process, and I think you can use the lcd for quite some time.