Abstract
Given that the induced stress resulting from fatigue bending
or torsional loads increases with increasing display thickness, the
long-term mechanical reliability of display modules in soft electronics
has attracted considerable attention. Therefore, understanding the
related failure mechanism and stress contour distribution in the display
structure is important and necessary, particularly in torsional load
application. This study introduces two important types of testing
loads (i.e., entire reverse of bend and torsion with several cycles)
to investigate the optical and flexible characteristics of film-type
cholesteric liquid crystal displays (ChLCDs). The bending radius and
the torsion angle used are 20 mm and
${\pm}{{10}}^{\circ}$
, respectively.
The stress contour and possible failure location of the testing specimens
are obtained by using non-linear finite element analysis (FEA). Results
indicate that a significant optical characteristic decay occurs beyond
1000 testing times. In 11,000 cycles of fatigue bending and torsion
tests, 45% and 55% decay change rates, respectively, are obtained
for the National Television System Committee. Accordingly, a worse
situation occurs at the torsion test. This phenomenon is attributed
to a two-direction bend torsion exerted on the tested ChLCD. The foregoing
behavior is validated by using FEA.
© 2015 IEEE
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