Inkjet Color Printing by Interference Nanostructures

Abstract

Color printing technology is developing rapidly; in less than 40 years, it moved from dot matrix printers with an ink-soaked cloth ribbon to 3D printers used to make three-dimensional color objects. Nevertheless, what remained unchanged over this time is the fact that in each case, dye inks (CMYK or RGB color schemes) were exclusively used for coloring, which inevitably limits the technological possibilities and color reproduction. As a next step in printing color images and storing information, we propose the technology of producing optical nanostructures. In this paper, we report use of inkjet technology to create colored interference layers with high accuracy without the need for high-temperature fixing. This was made possible due to using titania-based colloidal ink yielding monolithic coatings with a high refractive index (2.00 ± 0.08 over the entire visible range) when naturally dried. By controlling the film thickness by using inkjet deposition, we produced images based on controlled interference and implementing color printing with one ink. The lack of dyes in the proposed method has good environmental prospects, because applied systems based on a crystalline anatase sol are nontoxic and biologically inert. The paper explains in detail the principle of producing interference images by the classical inkjet method and shows the advantages of this technique in depositing coatings with uniform thickness, which are required for large-scale interference color imaging even on unprepared polymer films. This article demonstrates the possibility of inkjet printing of nanostructures with a precision in thickness of up to 50 nm, we believe that the proposed approach will be the groundwork for developing interference color printing approach and allow to implement new methods of forming optical nano-objects by widely available techniques.

Inkjet printing of transparent sol-gel computer generated holograms

“…To produce basic optical components by inkjet printing, we use titania-based inks [8]. A distinctive feature of most sol-gel inks is the ability to adjust viscosity and surface tension by diluting with alcohols [30].…”

“…Previously inkjet printing has been applied for producing various coatings ranging from conductive transparent films to optical coatings [6]. The development of nanoparticle-based inks allowed expanding [7] the applicability of inkjet printing to fabrication of micro and nanostructured solid objects with a resolution of up to 20 nm along the z-axis [8]. This technological advancement was the result of the unique properties of nanoparticles related to both their small dimensions and specific physico-chemical characteristics, which allow producing uniform layers [9] and induce self-assembly of materials [10] and specific packing on the surface of substrates giving rise to important properties of the resulting materials including new optical characteristics inaccessible to the respective bulk materials.…”

“…This renders a soft lithography of one-dimensional (1D) optical structures a very promising approach for the application in the inkjet technology. We have recently demonstrated the utility of this concept by developing the first interference printing technique [8,22].…”

UV-curable hybrid organic–inorganic composite inks with a high refractive index for printing interference images and holograms

“…Techniques based on inkjet printing of functional inks have been extensively discussed in the recent literature as practical approaches to directly pattern various classes of materials on supports for applications in electronics, 1,2 micromechanics, 3 biomedicine 4 and other areas. [5][6][7] In our previous studies, we have reported the development of functional inorganic inks for inkjet printing of well-defined heterostructures suitable for applications such as color interference images 8 and masking rainbow holograms. 9 Conventionally, the spatial resolution in inkjet printing of functional materials is limited to 10-20 mm as determined by a combination of factors such as the droplet diameters, placement errors and physicochemical characteristics of the inks.…”

“…Based on the interference spectrum, the refractive index of the films was calculated according to an example shown in ref. 8.…”