Anti-counterfeiting Technology Based On Rare Earth Up-conversion Luminescence

In daily life,the main way to prevent product counterfeiting is to design a unique anti-counterfeiting logo,which avoids the economic losses of many industries and even protects our personal safety.Fluorescent anti-counterfeiting technology has become an important application technology in the field of anti-counterfeiting because of its concealment,anti-counterfeiting and other characteristics.Rare earth up-conversion luminescence is a practical anti-counterfeiting material,which has a variety of luminescence colors and can realize the conversion from infrared to visible light.This work is oriented to the practical anti-counterfeiting application,developing new rare earth fluorescent anti-counterfeiting materials,designing anti-counterfeiting pattern and recognition system,in order to get an efficient,practical and high accuracy anti-counterfeiting system.The main work includes the following aspects:First,CaWO₄:RE³⁺/Yb³⁺(RE=Eu,Ho,Tm)up conversion fluorescent anti-counterfeiting material preparation,performance characterization and anti-counterfeiting pattern design.Because CaWO₄has the characteristics of good thermal stability,high density and low phonon energy,researchers found that CaWO₄has good luminescent properties.Eu³⁺,Ho³⁺and Tm³⁺have typical luminescence,so there is a good development space in the research of optical anti-counterfeiting labels.In this paper,CaWO₄:RE³⁺/Yb³⁺(RE=Eu,Ho,Tm)was synthesized by high temperature solid-state method.The emission spectrum was analyzed.Under 980 nm laser,CaWO₄:RE³⁺/Yb3³⁺(RE=Eu,Ho,Tm)emits red light at 616 nm,green light at 549 nm and blue light at 475 nm,respectively.The anti-counterfeiting pattern is designed based on these three materials.Secondly,based on Lu₂O₃,the fluorescent anti-counterfeiting materials were obtained by high temperature solid-state method,and the morphology and structure of the materials were characterized.Because Lu₂O₃has excellent thermal stability,electrical insulation,moisture resistance and no pollution to the environment,these properties make Lu₂O₃based phosphor materials can be better used in practice.In this paper,Lu₂O₃:Er³⁺/Tm³⁺/Yb³⁺and Lu₂O₃:RE³⁺(RE=Eu,Tb,Tm)were synthesized by high temperature solid-state method.The luminescent and excitation spectra of Lu₂O₃:Er³⁺/Tm³⁺/Yb³⁺were measured and analyzed as follows:according to the luminescent spectra,under 980 nm laser,it is found that blue light(478 nm)and green light(545 nm)exist in the light emitted by Lu₂O₃:Er³⁺/Tm³⁺/Yb³⁺.Under 283 nm and379 nm laser,Lu₂O₃:Er³⁺/Tm³⁺/Yb³⁺phosphors emit 478 nm blue light and 545 nm green light respectively.Lu₂O₃:RE³⁺(RE=Eu,Tb,Tm)samples emit red,green and blue light at 615 nm,543 nm and 460 nm respectively under the excitation of 298 nm,376 nm and 360 nm,respectively.Due to the different luminescent modes of Lu₂O₃based luminescent materials,anti-counterfeiting patterns were designed based on the characteristics of luminescent materials.Finally,using Python platform to complete the design of anti-counterfeiting image recognition system,in which the convolution neural network is used in the system,through this network structure to make up for the slow recognition speed and low accuracy of traditional recognition methods,at the same time,it also reduces the weight of the traditional network structure;through the gradient descent method to optimize the recognition system.According to the final experimental results,the accuracy of the recognition system designed in this paper can reach 96%,which also provides a reference for the application of neural network in anti-counterfeiting recognition.