jowilcox@xxxxxxxxxxxxxxxxxxx writes:
<< What causes an LCD to become useless? If one had two OM-4Ts of equal age
and used one and stored the other (this is hypothetical!), would the LCDs or
both
be done for at the same time, or do they in fact wear out from use?
>>
Hi Joel,
Early LCD's had short life (a few years) because of inadequate sealing
of the liquid crystal material from moisture. Seals were epoxy at the edge of
the glass. I believe in long term storage even today moisture sealing may be
the main problem. I don't believe the glass is frit sealed even today,
because the liquid crystal material is damaged by high temperatures required
for frit seals. (Maybe the chemicals have changed and now allow this?)
Some Liquid crystal materials are quite sensitive to UV so you
sometimes see yellow filtered LCD's which protects against UV. (not a
problem in an OM as the finder never sees direct sunlight for long and the
thick glass reduces UV anyway.
High temperature above about 50C causes the LCD material to become
inoperative although they usually work again at lower temperatures. Much
higher temperatures apparently cause permanent damage to the material.
Direct voltages across the LCD can damage it. I believe this is
related to the transparent tin oxide metalization on the glass and may be a
plating type phenomena.. To prevent this the drive electronics put AC
voltages accross the LCD but sometimes some residual DC voltage is present or
if the IC is damaged or the connector is faulty a DC offset can occur. The
vendor usually specifies a maximum offset voltage below which "no" damage
occurs but this may be partially exposure related. That is even at a very low
offset very slow degradation occurs so eventually after enough hours the
display fails i.e. a wear out phenomena.
Regards,
Tim Hughes
>>Hi100@xxxxxxx<<
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