Pic Dude wrote...

>There was a post yesterday about "leaking" LCD's, and I just
>remembered this...  Had a Sony CD walkman many years
>ago (one of the first very slim units) that had an LCD display.
>
>Left it on the car dash once and when I came back, the unit
>was really hot, and the display was completely black.  I tried
>some buttons, etc and nothing.  Thought it was hosed, but it
>came back after it cooled off.  And this happened many times
>since that, but it never did any permanent damage to the
>LCD.
>
>Wonder what was going on here?

The liquid crystal material in LCD displays has an upper
temperature limit above which it "switches" (I forget the proper
technical term for it) just like the liquid crystal goop inside
one of those fever thermometer strips.

The transition from clear to opaque is surprisingly abrupt; years
ago I was doing stress-testing on a design of mine that included
an LCD display, and found that the span of temperature over which
the display turned from clear to black was barely two degrees C.

Provided you don't take the LCD up to a temperature a LOT high
than this, the effect is harmless and reversible with no apparent
effect on the unit's life.

In short, what you saw was normal.

DD

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