Path: utzoo!attcan!uunet!isc-br!jimc
From: jimc@isc-br.ISC-BR.COM (Jim Cathey)
Newsgroups: sci.electronics
Subject: Re: Life of LCD Panels
Message-ID: <2881@isc-br.ISC-BR.COM>
Date: 2 Jul 90 20:36:45 GMT
References: <25269@unix.cis.pitt.edu> <3922@memqa.uucp> <1990Jun29.150402.6752@zoo.toronto.edu> <25522@unix.cis.pitt.edu>
Organization: ISC-Bunker Ramo, An Olivetti Company
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In article <25522@unix.cis.pitt.edu> nadst2@unix.cis.pitt.edu (Nilanjan Adhikari) writes:
>  It appears that the degradation requires a dc field to be present.
>Does that mean that for intermittently used lcd's (like those in a
>camera or a calculator), the degradation is practically of no concern ?
>Do lcd's deteriorate over time anyway, whether or not they are turned
>on ?  I came to know that Canon warns about a possible degradation of
>the lcd panels in their EOS series cameras after about five years.

In the case of EOS cameras, the LCD is powered up all the time there is
a battery in the calculator, so there really isn't any 'intermittent'
use.  Of course, it might depend on just how clever the designer of the
driver circuitry is.  Does anyone know the exact circuit details for
the common watch and camera type LCD's?  Are off segments merely
in-phase AC signals and on segments out-of-phase, or does an off
segment have zero potential placed upon it?  If it's the phase switch
kind of circuit, then slight differences in the drivers can result in
an average (albeit low) DC potential.  If it's completely decoupled
then what about microcurrents induced capacitively?

Of course, I'm not convinced that the 5-year specified life is due to
inevitable DC degradation effects and isn't something more like
chemical decomposition -- or maybe even a combination?  Or maybe just
CYA specsmanship 'cause no one's done an extensive test lately?