Research On Thinning Process Numerical Simulation And Forming Mechanism Of The Flexible Glass

Flexible glass with excellent properties of glass and plastic is a kind of new materials with great application value,which has been newly developed in the world.It is a major technological innovation of the glass manufacturing industry.Flexible glass has the characteristics of glass material such as high hardness,high transparency,good heat resistance,good electrical insulation,excellent air impermeability,and stable mechanical and chemical properties in an oxidizing and lighting environment.In addition,the biggest advantage of flexible glass is excellent bendability,compared with traditional glass material.The high temperature resistance of flexible glass can meet the requirements of some optoelectronic devices that must be processed at high temperature.At the same time,its outstanding bending and winding properties make it possible to use a continuous“roll-to-roll”printing process to produce various kinds of optoelectronic devices.Therefore,flexible glass will become the preferred substrate for flexible printed optoelectronic devices in the future,which may lead to an essential changes and great leaps in the flexible display and solar cell industries.At present,several major glass companies in the world have already exhibited flexible glass samples and formed a technology monopoly.However,products for application of flexible glass have not been reported.In recent years,China has made great progress in the field of ultra-thin flat glass,but the research of flexible glass is still blank and needs independent innovation.Based on the background of National Key Research and Development Program of China（the 13th Five-Year Plan）and“Double First Class”Project of Wuhan University of Technology,we started to carry this research project out.In this work,the key preparation technology of flexible glass was studied by slit down-draw method.Compared the computer simulation with actual conditions,the regularity of glass thinning process was revealed.On this basis,an experiment platform for stretching operation of flexible glass was firstly built in China.Finally,a flexible thin-film glass with a width of 12 cm,a thickness of 0.08 mm and a length of more than10 m was successfully produced,which realized the zero breakthrough of flexible glass in China.The major conclusions are as follows:（1）Numerical simulation of flow state for glass melt with slit down-draw method was carried out using Fluent software.The results show that the height of glass fluid（h_x）,the viscosity of glass fluid（η）,the width of glass slit（w_x）,and the stretching out length（l_x）all affect flow rate（Q）of glass melts.Their relationship can be concluded in an equation of Q=K h_xw_x²?l_xη,where the coefficient（K）changes with w_x.The error between measured value and simulated value is less than 5%.（2）Flow-3D software was used to simulate the state of tension and deformation of flexible glass by slit down-draw method.The relationship between the thickness of the glass plate（w）and the distance from the slit（h）can be described by the equation of w=ae^bh+c,where the coefficient c is the final thickness of flexible glass plate.The length of the root part of flexible glass plate is determined by a and b,and the curvature is determined by b.In addition,different values of a,b and c under different conditions are also provided for reference.（3）Through the physical stretching experiments of flexible glass,the relationship between the width and thickness of glass plate and the speed of the edger roller,the temperature of platinum leaking plate and the ambient temperature was studied.The results show that plate thickness(c_min)is changed as a function of the temperature of platinum leaking plate（T）and speed of edge roller（v）:c_min=AT³+BT²+CT+D;c_min=Kv ^E（Here,A,B,C,D,E and K are coefficients）.When the temperature of platinum leaking plate is over 1070℃,the flexible glass plate starts to fail to maintain the uniform width due to the surface tension of glass fluid.With the temperature less than 1070℃,there is a maximum matching speed of edge roller in a specific space temperature.If the maximum speed is exceeded,a“surge”phenomenon of periodic fluctuations in the plate width will occur,which is extremely harmful to flexible glass manufacturing.In this study,the temperatures of platinum leaking plate and space are optimized to 1045°C and 800⁸50°C,separately,and the speed of edge roller is 21.5mm/s,which help to produce the flexible glass with a thickness of 0.08 mm.（4）The distribution uniformity of the overflowing of glass melts by the overflow fusion down draw method was also simulated with Fluent software.Trough top inclination,glass viscosity,and inlet pressure were considered as the main influencing factors.It is concluded that the best way to adjust the distribution of glass melts is to modify the trough top inclination,and the optimized angle is 4°⁵°.The viscosity of glass melts less than 2000 Pa·s contributes to the uniform weight distribution of the glass melts.The inlet pressure has a significant effect on the adjustment of the overflow volume of the glass melt near the inlet,and the suitable pressure should be less than19600 Pa.