Physical shock induced ubble in LCD panel

[Samuel M. Goldwasser]

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.

--
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[Sjouke Burry]

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.

 

[N_Cook]

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.

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Vacuum bubbles are powerful beasts. See cavitation effect around ship's
propellors- pits the bronze. Maybe even cold-fusion, not the Fleichman-Ponns
one, sonofusion.

 

[Samuel M. Goldwasser]

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.

Yes, but my point was that this appeared away from any seam, and no
cracks were visible. So, it appeared without any access to air.

Thanks.

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[[email protected]]

Yes, but my point was that this appeared away from any seam, and no
cracks were visible. So, it appeared without any access to air.

Thanks.

Hi
There are two options that I see. Either the bubble was always there
along the edge and move by the shock or there is a leak on a seam.
The fact that its final resting place was in from the edge is not an
indication of where it came from.
As an example of an edge leak. The shock cause a band of vacuum
to from from the edge to some inner location. It also cracked the seam
at the same location as the end of the band of vacuum. A small
amount of air leaks in. The glass relaxes after the shock, allowing
the liquid crystal to attach back to the glass until the pressure of
the bubble got high enough because of the smaller size.
So, you see, it could have come from anywhere. If it was a leak,
the LQ will degrade over time.
Dwight