Physical shock induced ubble in LCD panel

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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Reply to
Samuel M. Goldwasser
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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.

Reply to
Sjouke Burry

seen

is

in the

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.

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Reply to
N_Cook

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.

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Reply to
Samuel M. Goldwasser

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

Reply to
dkelvey

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