Research On The State Transition Law Of Polymer Based On The Continuous Injection Direct Rolling Of Ultrathin Light Guide Plate

With the development of science and technology,the application of large-scale LCD is more and more extensive.How to produce wide and large ultra-thin light guide plate with low cost and high efficiency has become a research hotspot.The technology of continuous injection direct rolling(CIDR)provides a new way for the forming of ultra-thin large-scale wide-width micro structure polymer plate.The technology combines the characteristics of injection compression molding and rolling hot stamping molding,and can continuously produce ultra-thin large-scale wide-width micro structure light guide plate through injection filling and finishing rolling.In this paper,based on the technology of CIDR,a series of research on the state transition law of polymer light guide plate forming process in the injection-rolling zone is carried out,and the forming process is optimized.At first,the rheological properties of polymers under the same conditions of CIDR were studied.The shear viscosity of amorphous polymer polymethyl methacrylate(PMMA)melts with die sizes of?0.3mm,?0.5mm,?1.0mm and?2.0mm were measured by single barrel capillary rheometer,the viscous activation energy and non-Newtonian index properties of polymers based on characteristic size were studied.Then,the rheological law of PMMA melt is analyzed and the viscous activation energy model(SVAE model)and non-Newtonian index model(SNNE model)based on feature size were established.This method can calculate the viscous activation energy and non-Newtonian index of polymer materials conveniently and accurately,and provides some theoretical guidance for the selection and optimization of processing parameters of CIDR.In view of the temperature transformation characteristics of polymer materials in the injection-rolling zone during CIDR,considering the influence of heat radiation,heat conduction and plastic deformation on the polymer melt transformation in the injection-rolling zone,the theoretical model of temperature field of ultrathin light guide plate in different deformation zone of injection-rolling under different rolling speed,different reduction rate and different roll temperature was established by combining with mathematical analysis method.Then based on the theoretical model of the temperature field,the temperature field of polymer forming and flowing process in the injection-rolling zone is numerically solved by fluent finite element software.It is found that the boundary of the traditional finite element numerical calculation model was modified by the mathematical analytical theoretical model of the temperature field in the deformation zone of injection-rolling,which improves the prediction accuracy of the finite element numerical calculation;the average error was only 2.4%.The actual situation of temperature field change in the injection-rolling zone during CIDR process can be described more accurately.Based on the theoretical model of the temperature field in the injection-rolling zone,a steady-state thermo fluid coupled finite element model was established.The influence of the injection temperature,injection speed,roll temperature,roll speed,reduction rate and other process parameters on the polymer melt state transition(R_S point of the high elastic transition line,G_Spoint of the glass transition line)and the flow field in the injection-rolling zone was analyzed.A comprehensive prediction model of the horizontal distance between R_S point and G_S point and each process parameter is established.The horizontal position of R_S point and G_S point corresponding to PMMA light guide plate with better quality of the injection rolling exit is analyzed,and the optimal molding process parameters of each CIDR are calculated.Finally,PMMA ultrathin light guide plate was produced by continuous casting and rolling,and high quality ultrathin light guide plate was successfully manufactured.It is found that the temperature control at the exit of the plate is in good agreement with the calculated value of the numerical theory,and the thickness of the plate is uniform as a whole;the replication rate of V-shaped microstructure of various sizes on the surface of the light guide plate is high,and the forming accuracy of the microstructure is high;the maximum transmittance of the light guide plate is 90.2%,and the haze is 0.51%,which meets the optical performance requirements of the optical devices.The results show that the research on the transformation mechanism of polymer forming state in the injection-rolling zone is helpful to improve the quality of products.