Preparation Of An Anti-counterfeiting Film With Stereoscopic Display Different Graphics At Different Viewing Angles On The Basis Of Surface Micro Lens Array

On the basis of the relationship between the size parameters of cylindricallens and printing parameters, the CMYK printable files of PDF graphic, that areused for the Offset printing plate making are obtained by Adobe Photoshopand PSDTO3D three-dimension software. Three kinds of anti-counterfeitinglabels of three-dimensional stereoscopic were manufactured by Offset printing.The labels has anti-counterfeiting function of copy-prevention andscan-prevention, which origins from the effects of “displaying different graphicsat different viewing angles”,“switch”, and “stereoscopic”. The relationshipbetween cylindrical lens curvature radius R, the refractive index n andthickness d isd=nRn1, the double viewpoints column cylindrical lensimaging parameters relationship isKOL=2P,O K+LJ=L. J is cylindrical lensanti-counterfeiting film gate width, O is pixel spacing for, K is the distance oflens focus plane to graphic layer, L is the human eye observation distance, P isthe spacing between human eyes (usually65mm).Size parameters of micro lens array film that would display effects of“motion”,“displaying different graphics at different viewing angles”, and“stereoscopic”, were obtained by analyzing. They areK=25.4L, h=24K,d=K+24K, D=h+d.While, K is a micro lens array width, L is the linenumber, h is the spherical cap height, d is the thickness of the imaging, D is thethickness of the film. Based on this, a hexagonal micro lens array PC(polycarbonate) film was prepared by a roll-to-roll, circle hot pressure circleway. The mold was prepared by laser micro-engraving technology. The hotpressing temperature is140℃and the speed is5meters per minute.Hexagonal micro lens’s side length32μm, lattice spacing K is47μm, film thickness D is125μm, the line number L is540. The CMYK printable files ofPDF graphic, that are used for the Offset printing plate making are obtained byAdobe Illustrator CS5software. Then four-color Offset printing. However,through those processes, the prepared labels did not have stereoscopic effects.The reason is that the printing micro-graphics did not align to single micro lensaccurately enough for the “stereoscopic” effect. Generally, the size accuracyof printing is more than20microns. The elongation of PC thin film in theprinting process is difficult to control. So, the method of printing graphic on thethin (less than125μm)plastic film to prepare stereoscopic anti-counterfeitinglabels with super effects is too difficult and low feasibility. It is necessary toexplore a new preparation method.