On substrate behavior of flexible displays subjected to torque

Abstract

In contrast to liquid-crystal displays (LCDs) and light-emitting-diode (LED) displays, flexible displays allow deformation. Therefore, it is worth studying the deformation of substrates in flexible displays. In this work, an analytical derivation is carried out for the torsion behavior of flexible substrates. Comparisons are made between deflection results of linear and non-linear elasticity analyses for substrates subject to four corner forces and torque, respectively. They show that when deflection becomes large, torques or forces needed for unit deformation also increase. Simulation results also show that when the substrate aspect ratio of length/width in display sizes increases, displays are easier to deform under torsion. In addition, polyethylene terephthalate (PET) substrates subject to torque are compared with polyethylene naphthalate (PFN) substrates. Finally, in experiments a fringe-reflection method and a four-step phase-shifting technique were carried out to validate the proposed non-linear model.