Research On Anti-counterfeiting Technology Based On Dynamic Display Using Microstructures

As known,fake and inferior products of cigarettes,wine,medicines and other goods not only influence the legal interests of legitimate firms,but also endanger the health of consumers.In order to distinguish the fake from the original,several anticounterfeiting techniques were developed,such as holography,QR code,watermark and so on,which played a positive role in the past.However,due to the technological stagnation,technological disclosure and poor visual effect of these techniques,the quality of goods remains uneven at present.Every year,a large number of fake and inferior products are seized and destroyed,which are worth billions and usually a tiny minority.If we let the crime go and keep rampant,the fake products will disturb the stable order of Chinese economy.With the development of anti-counterfeiting techniques,dynamic display anti-counterfeiting technique based on microstructures appears,which has a better visual dynamic effect and can combat crimes of counterfeiting more effectively.The appearence of the microstructural dynamic display anti-counterfeiting technique depends on the development of mirolens arrays.Compared with classic lens arrays,microlens arrays have the features of light weight,small size,high integration and sensitivity,and so on,which have been applied for guidance system,monitoring devices and medical endoscopes and other equipments.With microlens arrays,dynamic display technology can realize varying visual patterns,which has a strong dynamic effect.It requires effective design method and complex fabrication process.Therefore,it is much more fit for the purpose of anti-counterfeiting.It can be seen from the domestic and foreign research status that a few domestic scientific research institutes are able to fabricate microlens arrays,who mainly concentrate on experimental study.Although methods like thermal reflow,ion exchange and electric drive etc.are proposed internationally to fabricate microlens arrays,the shape controling and fabrication of microlens arrays is still the research focus,aiming at reducing the cost and improving the accuracy of shape controlling.As for dynamic displaying anti-counterfeiting technology based on microstructures,the microlens array is one of the most critical optical elements that decides the image quality.At present,microlens arrays used in dynamic display still has the problems that the design method is incomplete,the display mode is simple and the production costs heavily.Aiming at the microstructural dynamic display anti-counterfeiting technology,the theory is studied and developed.Based on the theory of dynamic display,the imaging principle is studied.The relation of the image quality and the parameters is considered systermatically.The fabrication process of dynamic display anti-counterfeiting label is implemented.Samples of anti-counterfeting labels are obtained with ideal visual effect through experiments.It can lay a foundation for the development and application of dynamic display anti-counterfeiting technology.The research works mainly include:(1)Research status of optical anti-counterfeiting technology and fabrication thchnology of microlens arrays at home and abroad is introduced.The imaging pricinple of dynamic pattern is analized based on moiré models.The theory is developed.The design method of the key parameters of dynamic display system is proposed.(2)The individual dynamic pattern is proposed,which realizes a single pattern and breaks the size restrict of the classic dynamic pattern.The principle of individual dynamic pattern imaging process is analized,and the micropattern arrays are obtained by capturing and reconstruction method.Aiming at the cross-interference of individual dynamic patterns,the reason is analized and an optimization method is proposed based on improved micropattern arrays.A method for dividing the viewpoints is studied,which realizes dynamic pattern displaying at desired viewpoints by choosing the effective areas of micropattern arrays,so that the pixels can be captured by the corresponding microlenses.(3)Based on the study of microstructural parameters of dynamic display,methods of realizing different dynamic effects are developed.As for dynamic pattern in an array,the design methods of period,orientation and displacement are proposed and compared.Meanwhile,in the situation of multi-dynamic patterns,approaches for achieving the free motion,relativel motion and orthogonal motion are suggested.As for the individual dynamic pattern,Glass pattern based on random arrays and individual dynamic pattern based on periodic arrays are both studied.Three-divided perspectives for multidynamic patterns is presented.(4)The relation between microstructural parameters and image quality is studied.Rays in dynamic display system are analyzed based on ray tracing method.Microlens' s structure is improved by using second order aspherical surfaces.After transmitting through the system,the divergent angle of the rays is calculated.The relationship of conic coefficient and divergent angle is established,and optimal parameters are obtained.Aiming at the impact of observation distance on the dynamic pattern quality,the design of micropattern array period is modified.Dynamic display system and imaging process are simulated by ZEMAX software.The simulation results validate the proposed optimization methods.(5)Fabrication process for the microstructures of dynamic diaplay anticounterfeiting film is studied.Aiming at microlens arrays and micropattern arrays,micro fabrication and transferring technology are studied.The superposition of microlens arrays and micropattern arrays on the anti-counterfeiting film is realized by the PDMS transferring technique and roll to roll continuous imprinting technique.The fabrication process is studied as well.The fabricated microstructure is measured and the display effect is analized.