Research On Polyvinyl Chloride Gels-based Microlens Array With A Well-controlled Curvature Obtained By Solvent Evaporation Under DC Electric Fields

As an important micro-optical element,microlens array which attracts many researchers’ interest has been widely used in the fields of display,imaging,transmission,mapping.Various fabrication technologies of microlens array have been proposed.Different fabrication techniques are suitable for different materials and application scenarios.Based on the unique electrodeformation characteristics and excellent photoelectric properties of polyvinyl chloride(PVC)gels,a fabrication method of PVC gel microlens array based on electric field induction molding was proposed in this paper.By applying DC voltage on the surface of the ring-array-patterned electrode substrate,the solvent in the polyvinyl chloride gel solution was volatilized.Electronegative plasticizer molecules migrate to the anode and accumulate on the surface of anode.After the solvent volatilization thoroughly,PVC gels-based microlens array with specific curvature are obtained.The main content and work are as follows:1.To prepare PVC gels for fabricating PVC gels-based microlens array,10 wt.% PVC power and 90 wt.% plasticizer were dissolved in the solvent at room temperature.The properties of PVC gels and PVC gels solution were characterized by a variety of test instruments,including UV-Vis spectrophotometer,Abbe refractometer,LCR tester and thermogravimetric analyzer.The transmittance of PVC gels film in visible light was measured by UV-Vis spectrophotometer.The refractive index of PVC gels at room temperature(20 ℃)was measured by Abbe refractometer.The dielectric constant of the PVC gels solution and its components were measured by LCR tester.The thermogravimetric analysis instrument was used to obtain the thermal weight loss of the PVC gels to understand its thermal stability.Based on above mentioned properties of PVC gels,the feasibility of using PVC gels to fabricate microlens arrays was analyzed.2.PVC gels-based microlens array with controllable curvatures prepared by evaporation of the solvent under direct current(DC)field were reported.A ring-arraypatterned electrode structure was designed and prepared by photolithography technology.The electric field distribution of the ring-array-patterned electrode was analyzed by using COMSOL Multiphysics finite element simulation software.In order to verify the feasibility of the experiment,the distribution of PVC gel in different regions of the annular pattern electrode substrate with and without electric field inducing were analyzed by micro infrared spectroscopy.Then the preparation processes of PVC gels-based microlens array were introduced,and the performances of the produced PVC gels-based microlens array were evaluated.The surface morphologies of PVC gels-based microlens array were measured by metallographic microscope.The cross-section profiles of PVC gels-based microlens were measured by using white light interferometer.The focal lengths were calculated if the sag heights microlens were known.The focusing properties of PVC gels-based microlens array were tested by self-built experimental setup.The imaging properties of PVC gels-based microlens array were tested by optical microscope.Based on the above test results,the feasibility of manufacturing process of PVC gelsbased microlens array was proposed.3.The influences of fabrication processes for PVC gels-based microlens array prepared by the evaporation of the solvent under a DC electric field were studied.If the structure of the ring-array-patterned electrode and the volume of the PVC gels solution were fixed,the curvature of the PVC gels-based microlens can be adjusted by varying the inducing voltage.If the structure of the ring-array-patterned electrode and the inducing voltage were fixed,the curvatures of the PVC gels-based microlens array can be tuned by changing the volumes of the PVC gels solution.PVC gels-based microlens array with different sizes and fill factors were prepared by designing the inner zone’ diameters and the arrangement of inner zones of the ring-array-pattern electrode.By analyzing the crosssection profiles and imaging properties and focusing propertied of the PVC gels-based microlens array,the optimized processing parameters for preparing PVC gels-based microlens array were obtained.The above research provides experimental method and theoretical support for the fabrication of PVC gels-based microlens array.