A team of researchers from ITMO University, Russia, has come up with a new method by which ordinary inkjet printer can be used to make vivid holograms.
To make the holographic images and texts printable, the team developed colorless ink made of nanocrystalline titania (TiO2) which can be loaded into an inkjet printer and then deposited on top of exposed poly(ethylene terephthalate)-based microembossed paper. The findings were published in the journal Advanced Functional Materials.
As researchers put it, the whole process of obtaining holographic images may take up to several days and even more, temperature must be accurately set. However, the new nanocrystalline ink makes it possible to cut down both the expenditures, temperature maintenance and times to create rainbow holograms. Because for this, ordinary inkjet printer is used as a primary hardware.
“The conventional way of preparing a hologram is incredibly time-consuming and consists of several stages. First of all one needs to create a master hologram, which is usually laser recorded on a thin layer of photosensitive polymer. The polymer is then dried and unexposed parts are washed out,” explained Aleksandr Yakovlev, lead author of the study and researcher at the SCAMT laboratory. “The resulting stencil is then transferred to a metallic matrix, which eventually serves to emboss holographic microrelief on the surface of a transparent polymer film.”
“Printing separate holographic images in a quick and effective manner is a challenge that, until now, has been unresolved,” he added.
For this new method, the operation is simple. The ink is applied with a simple inkjet printer on a microembossed surface, which is later on covered by varnish. The holographic image is exclusively seen in those areas where the protective ink was deposited.
“The peculiarity of our ink lies in its high refractive index in all visible range of light,” said Alexander Vinogradov, one of the researchers. “The use of nanocrystalline ink forms a layer with high refractive index that helps preserve the rainbow holographic effect after the varnish or a polymer layer is applied on top.”
The team said that the new techniques makes it easy to obtain holograms of practically any size. And also with reduced maintenance, it makes the whole process cheaper.
They also believe this new technique could significantly reduce the cost and time needed to create the so-called rainbow holograms, commonly used for security purposes – to protect valuable items, such as credit cards and paper currency, from piracy and falsification.