Research On Folding Process And Bending Performance Of Flexible AMOLED Screen

At present,the active matrix organic light-emitting diode(AMOLED)flexible screen gradually replaces the traditional OLED screen because of its advantages such as selfluminous,low energy consumption.However,in the process of AMOLED screen use and production,there are problems such as low bending performance and screen body peeling.The bending method and temperature are important factors in determining the bending performance and quality of flexible screens,and are also key factors in whether flexible screens can be commercialized into production.In this paper,based on the simulation modeling of the stacked structure of AMOLED flexible screen,we analyze the force situation of flexible AMOLED module under different bending methods and the deformation situation under different ambient temperatures,and study the creep process of flexible AMOLED under different temperatures.The main research contents are as follows:(1)Uniaxial tensile and creep experiments were conducted on each film layer material of AMOLED module to obtain its basic mechanical parameters.Subsequently,the simulation parameters are determined based on viscoelastic theory,and finally the simulation of the bending process based on Maxwell’s instantonal equation and creep theory is carried out with the help of ABAQUS software.(2)Bending structural mechanics simulation analysis of the flexible screen model to obtain the optimal thickness of the screen and bending method.The single-fold and doublefold teardrop models of the flexible screen were established to compare the stresses of the models under the action of different bending methods and analyze the changes in the position of the neutral layer after the two bending methods;the stresses in the longitudinal direction of the OLED layer were analyzed for risk;the thickness of the OLED layer substrate(70～90 μm)was changed for stress analysis.The results show that: single-fold compared to double-fold,the Mises stress of the OLED layer is not much different,the longitudinal stress is smaller by 3 MPa.the position of the neutral layer of each film layer of flexible AMOLED basically overlaps,single-fold is the better bending method.the OLED layer in the longitudinal direction at 5.56 mm stress concentration.As the thickness of OLED layer increases the longitudinal stress of each film layer decreases,the stress of OLED layer is reduced by 13.63 MPa,and its optimal thickness is 90 μm.(3)The creep static bending of the flexible screen module at 20℃;the maximum stress analysis of the protective cover and support plate in the flexible screen module in the temperature range of-40～120℃;the analysis of the effect of the surface layer on the strain of each film layer under different elastic modulus and thickness parameters;the analysis of the creep rate and stress-strain of the surface layer;the comparison of the creep rate and stress-strain of the surface layer at 20℃,40℃,60℃ and unset temperature environment.The fracture strength and elongation of the surface layer under 20℃,40℃,60℃ and unset temperature environments were compared.The results show that the strain of the OLED layer is 0.13% when the flexible screen module is bent statically at 20℃,which is the lowest strain in the module.The protective cover plate reached the maximum stress-strain in bending at 80°C,with a stress of 63 MPa and a strain of 0.15%.As the temperature increases,the stress-strain of the support plate increases.The strain of the optically clear adhesive layer(OCA)decreases with the increase of the elastic modulus of the protective cover plate.The strain in the OLED layer is smaller for a support plate thickness of 75 μm.The strain of the protective cover plate grows more stably during creep,with a maximum strain value of about 1.11%.The fracture strengths of the protective cover plate and the support plate at20 °C are 98 MPa and 106 MPa,respectively,and the elongation at break of the module increases with the increase of temperature.