WO2017065640A1

WO2017065640A1 - Method of preparing sol-gel inks for color interference inkjet printing

Info

Publication number: WO2017065640A1
Application number: PCT/RU2016/000676
Authority: WO
Inventors: Александр Валентинович ВИНОГРАДОВ; Владимир Валентинович ВИНОГРАДОВ; Александр Вячеславович ЯКОВЛЕВ
Priority date: 2015-10-12
Filing date: 2016-10-07
Publication date: 2017-04-20
Also published as: RU2618064C2; RU2015143537A

Abstract

The invention relates to a method for producing a sedimentation-stable sol of crystalline nanoparticles of titanium dioxide to be used as sol-gel inks for color interference inkjet printing which allows for producing printed products with color interference images. The present sol-gel inks are produced in two stages: the first stage involves producing a nanocrystalline sol of titanium dioxide, preferably in the anatase phase, in water; the second stage involves producing sol-gel inks in the form of a nanocrystalline sol of titanium dioxide in an alcohol in water solution, having the requisite density, viscosity and surface tension for inkjet printing. The present invention provides the possibility of forming optical film nanostructures from a nanocrystalline sol of titanium dioxide by inkjet printing, and of producing interference images with high adhesion to a non-porous substrate.

Description

METHOD FOR PRODUCING ZOL-GEL INK

FOR COLOR INTERFERENCE INKJET

Technical field

The invention relates to inorganic chemistry, and in particular to a method for producing a sedimentation stable sol of crystalline titanium dioxide nanoparticles, mainly in the anatase phase, used as a sol-gel ink for color interference inkjet printing, which allows to obtain printed products with color interference images formed by at least one transparent in the visible region of the light spectrum and in the region of the UV light spectrum by the refractory layer of xerogel of titanium dioxide with a thickness of 300 nm to 1 μm, with a refractive index of more than 1.7 and a varying color depending on the thickness of the refractive layer.

State of the art

Color printing technology is booming and in less than 40 years it has gone from matrix printers with ink ribbon to 3D printers with the printing of bulk color materials, but the use of a color scheme for coloring CMYK or RGB dyes remains unchanged, which inevitably limits technological capabilities and color rendition.

Color inkjet printing is the most common and affordable, but color inkjets and specialty papers are usually required to print color images for inkjet printing.

At the same time, inkjet inks of some colors are environmentally hazardous, for example, yellow ink is usually made using toxic cadmium (Cd) compounds, and color images printed with conventional inkjet ink fade from exposure to sunlight, UV radiation and high temperatures.

In addition, high-quality color images by inkjet printing can be obtained only when using inks with certain physical properties (of a certain viscosity and surface tension) and on porous substrates (usually on special types of paper on which ink is absorbed but not fuzzy), which after ink dries usually deformed.

Known ink for an inkjet printer, and a method of inkjet printing with the suppression of the phenomenon of twisting of printed materials and stable ejection, including 62-77 wt.% Water, 10-18 wt.% Dye, 2.0-15 wt.% Water-soluble organic substances, including X (%) of water-soluble organic matter 1, and Y (%), water-soluble organic matter 2. Moreover, the ink viscosity is from 1 to 5 cP at 25 ° C, and the content of X (%) of substance 1 and the content of Y (%) of substance 2 satisfies the ratio of formulas (I) and formula (II): (I) 0.15 <Y / X <0.9; (I) 15 wt.% <Χ + Υ <32 wt.%. Compound 1 is a water-retaining water-soluble organic compound having a difference between the water-holding ability in an environment with a temperature of 23 ° C. and a humidity of 45% and the water-holding ability in an environment with a temperature of 30 ° C. and a humidity of 80% at 36% or less. Compound 2 is a water-soluble organic compound other than dye and water-soluble organic compound 1 [RU 2329288C09D1 1/00, B41J2 / 01, B41M5 / 00 Publ. July 20, 2008, WO 2005/087879 (September 22, 2005)].

Known ink, device and method of inkjet printing with ink viscosity of 100 mPa ink or less based on 50 to 80 wt.% Organic solvent capable of evaporation from printed ink. The paint includes a UV-curable material, a polymer that is studied by the free radical polymerization mechanism, photoinitiator and dispersible dye. The radiation curable material contains a UV curable oligomer having a polyester, urethane or epoxy backbone, a molecular weight of from 500 to 4000 and a viscosity of from 0.5 to 20 Pa-s at 60 ° C. The ink jet printing apparatus for said ink includes a printing mechanism, a device for evaporating the solvent from the ink, and a UV radiation source. The inkjet method using this ink provides coatings on substrates, including non-porous surfaces, with increased resistance to solvents and dry friction [RU 2561095 C09D1 1/00, C09D1 1/10, B41J2 / 00, B41J1 1/00 Publ. 08/20/2015, WO 201 1/021052 201 1.02.24].

A known method of obtaining a composition of polysiloxane and organic titanate comprising a siloxane photopolymer containing titanium, designed to produce a coating with a high refractive index and is resistant to abrasion to protect spectacle lenses made from organic glasses, which includes, as the first component of the photopolymer, anhydrous alkoxysilane hydrolyzate obtained by hydrolysis organosilane. As a second component, the photopolymer contains a titanium carboxylic acid ester having the formula (RCOO) HTIR '(4-η) (I), where N is an integer from 1 to 4 inclusive, R is the number of hydrogen atoms or alkyl groups with 1- 5 by carbon atoms, and R 'represents a hydrogen atom, a hydroxyl group, or an alkoxy group of 1-5 C atoms. The reaction of these first and second components is carried out until the formation of the specified titanium siloxane photopolymer in the absence of added water. After the addition of water and hydrolysis of the ι idrolizable groups, a further polymerization takes place to obtain a stable aqueous sol containing 20-30% by weight of Ti _2, relative to the mass of solid materials of the final KOMno3Humi [US5357024 C08G77 / 58; C08G79 / 00; S08K5 / 09; C08L83 / 04; C09D183 / 04; C09D183 / 14; 1994.10.18].

Known printed product, including a substrate and an image printed by a combination of colors of six inks of different colors. Each of the colors is defined by a predetermined ink ratio having a full tone of a given color and a halftone of a given color. Each of the six inks has a combined color difference dE of the full tone L-C-H-a-b of not more than 2. Ink is combined on the product to produce colors other than six ink colors. Each of the six inks has a combined color difference of dE halftone of no more than 3. Each of the six colors contains one or two pigments. A method of printing an article on an analog printing device includes preparing an electronic data file of a given artistic image, including the specified colors for the corresponding elements of the artistic image. Perform test printing of the artistic image by printing a data file using a digital printing device. Printer settings are combined with an electronic art image file. Provide multiple print locations with copies of the combined parameters by setting up a printing device and an electronic file containing visualization of the art image. Using the combined settings of the printing device and the electronic data file of the artistic image, copies of the product are printed dotwise, forming a complete picture of the composed image. [RU 2468923 B41M1 / 14 publ. 12/10/2012, WO 2009/083857 2009.07.09].

A known method of manufacturing multicolor printing reproductions, which consists in sequentially applying to the surface of the printed material of colorful layers of various colors, carrying monochromatic raster images with different raster lines, according to which, to improve the quality of reproductions, the raster lineature for each monochromatic image is selected from the dependence a / b * [(r _b- r _to UR _b ] -0.0007, where a is the raster pitch; b is the distance from the observer's eye to the image in question; p _b is the reflection coefficient of the printed material; p _to -reflection coefficient of the corresponding paint [RU 2043199 V41M1 / 14 publ. 09/10/1995].

Known grayscale image obtained by printing on a substrate, which consists of at least two types located in the form of a raster image points of different colors. The desired color is obtained by mixing the colors of the dots of the image, and fluorescent image dots of printing inks are formed on the substrate, which contain pigments fluorescent when excited by a certain electromagnetic radiation, as well as non-fluorescent image dots of printing inks containing color, non-fluorescent pigments when excited by a certain electromagnetic radiation. Moreover, these fluorescent image points and non-fluorescent image points are placed on a substrate in a checkerboard pattern relative to each other. This ensures the obtaining of a grayscale image, which is distinguished by high gloss and close to real color rendition [RU 2264296 V41M1 / 14 V41MZ / 14 B42D15 / 10 Publ. 20.1 1.2005, WO 03/01 1606 (02.13.2003)].

Known inks for color inkjet printing do not allow to obtain color interference images.

The phenomenon of interference in thin films is known, which is characterized by the fact that at the phase boundary of materials differing in optical density, a reflected beam is formed with a wavelength equal to the thickness of the material layer with a large refractive index (RI), which is perceived by the human eye as monochromatic color. In particular, interference is observed in soap bubbles (air / surfactant in water), in the iris multilayer mother of pearl structure.

An important advantage of interference is the natural color reproduction, since the entire spectrum of sunlight is used to form the interference image, including the maximum possible number of colors and shades perceived by the human eye.

However, the saturation of the color, which is responsible for the contrast of the resulting image, largely depends on the magnitude of the difference in the refractive indices of the applied layer and the substrate used.

To enhance this effect, attempts were made to modify polymers using various nanoscale crystalline substances.

Such approaches made it possible to obtain a high refractive index for organic polymers, however, the optical properties of organic polymers deteriorated sharply due to the lack of a homogeneous distribution of components between themselves and technologically unsolved problems of forming films of a given thickness with an accuracy of 10 nm, complementary to the structure of the light wavelength .

An alternative to physical methods for producing interference films (by laser spraying, thermal calcination, laser excitation of metals in oxygen with the formation of oxide layers, vacuum deposition of “masks”, etc.) can be the preparation of inorganic polymer films by solution chemistry methods. In particular, the technology of low-temperature sol-gel synthesis, which makes it possible to obtain monolithic film crystalline materials at low temperatures and atmospheric pressure, is considered the greatest prospect.

Langlet et al. Showed the application of this technology in the field of creating TU ₂ coatings for optics and creating photo-catalytic coatings on films.

Known scalable monochromatic interference on a smooth surface, formed either by a liquid phase or a solid substrate with a minimum roughness, for example, the artificial preparation of interfering layers on polished silicon and solid organic polymers.

The phenomenon of interference in thin films is known, which is fundamental for the appearance of an iridescent effect when creating chameleon paints.

The appearance of color in the microstructures of photonic crystals and colloidal magnetic materials is known, however, all known methods of creation and interference are not suitable for color inkjet printing.

Inorganic colloids are currently actively used for the film printing of biosensors and electronics, but their application for inkjet color printing is unknown.

However, until now, the capabilities of inkjet printing have been focused by the microrange, that is, by the formation of image elements at the micron level, greater than the wavelengths of light.

Therefore, it is urgent to develop previously unknown inkjet printing technologies for inorganic nanostructures with an accuracy of up to 10 nm in thickness to create the basis for the development of a new stage in the development of color inkjet printing and to develop fundamentally new interference methods for forming optical structures of nano-objects by inkjet printing methods.

Inkjet printing requires fine-tuning the viscosity and surface tension of the ink or fine-tuning the printer for a specific ink composition. In most cases, additives such as glycerin are used to increase viscosity and surfactants to reduce surface tension. This inevitably reduces the refractive index, due to an increase in the volume fraction of the organic part in PT / RU2016 / 000676

8 solids.

Known thin-film element with an interference layered structure for tamper-resistant papers, valuable documents and similar objects, containing at least two translucent absorbing layers and at least one dielectric separation layer located between at least two absorbing layers. Each of the two absorbing layers consists of a material having a complex refractive index N, the real part of n and the imaginary part of which differ at least in the visible spectral region by 5 or more times, when observed in reflected light, the thin-film element has a metallic luster and essentially a neutral color, and when observed in transmitted light it is perceived in color, in transmitted light the thin-film element has a color saturation C _a , defined in the CIELAB color space, of more than 15. Two p the absorbing layers consist of different materials, the real part nl and the imaginary part kl of the material of one of the two absorbing layers differ 5 or more times, at least in the visible part of the spectrum, and the real part n2 and the imaginary part k2 of the material of the other the two absorbent layers differ 8 or more times, preferably 10 or more times, particularly preferably 15 or more times. One of the absorbing layers or both of the absorbing layers are made of silver or aluminum. The dielectric separation layer is made of SiO _x or MgF ₂ . In transmitted light, the thin film element has a chroma C ^* _{ab is} determined in CIELAB color space, more than 20, preferably greater than 25. The thin film element when viewed vertically - is visible in transmitted light and has a green color saturation C ^* _ab of more than 30, preferably more than 40, or - in transmitted light is visible in yellow and has a color saturation C ^* _ab more than 20, or - in transmitted light is visible in red and has a color saturation of C _a b greater than 20, preferably more than 30, or - in transmitted light is seen in blue and has a color saturation of C ^{* a} _b greater than 20, preferably more than 30 or a thin film element in transmitted light is visible in color and shows the effect of change colors. The thin film element may be combined with a color filter, preferably with a color print layer or a color spray layer. The thin film element is combined with a relief structure, in particular, deposited on a diffraction relief structure or micro-optical relief structure [RU 2514589 B42D15 / 00 Publ. 04/27/2014, WO 201 1/032665 201 1.03.24].

A known method of obtaining diffracting images in crystalline colloidal arrays comprising: forming on the substrate an ordered periodic array of particles, where the array of particles diffracts in the wavelength band, depending on the viewing angle; printing the image composition into parts of the array in the image configuration; shifting the wavelength band of the diffracted radiation and / or changing the refractive index in the printed part of the array, so that the printed part diffracts the radiation with a wavelength band and reflection intensity different from the rest of the array; and fixing the printed part of the array in such a way that the printed part of the array diffracts the radiation and displays an image. The composition of the image changes the size and refractive index of the particles in the printed part of the array, resulting in a shifted wavelength band diffracted by the printed part of the array. The composition of the image contains monomers that change the size and refractive index of the particles in the printed part of the array, and additionally contains a solvent that resizes particles having a core-shell structure by changing the size and refractive index of the particle shells. The composition of the outer layer coating provides coalescence of the particles of the array in the printed part to obtain a film showing the image in the printed part, where the rest of this is almost colorless. The printing step includes applying the image composition by xerographic printing, inkjet printing, flexographic printing, silk screen printing, metallography or intaglio printing. The image composition provides a shift of the diffraction wavelength of a part of the array in the image printed using the image composition, so that part of the array in the image printed using the image composition diffracts the radiation at a wavelength different from the rest of the image [RU 2013125497 O02B 1/00 Publ. 12/10/2014, WO 2012/061207 2012.05.10].

Known protective printing fluid and method of printing with nanoparticles, which allows to protect printed materials from fake reprints, for example, in the manufacture of banknotes, stocks, checks and other valuable papers. Printing fluid for printing through narrow nozzles on objects, in particular in the manufacture of banknotes, stocks, checks, contains a carrier medium and nanoparticles of metal salts in the form of crystalline solid particles with an average diameter of less than 300 nanometers, fluorescent or phosphorescent when excited by UV radiation of range A , B or C or visible light. The emitted fluorescence or phosphorescence radiation does not lie in the frequency range of visible light, the frequency range of the excitation and the frequency range of the emission are shifted in frequency. Nanoparticles contain subsidizing additives of at least one type with a range of excitation frequencies and a range of emission frequencies for fluorescence or phosphorescence. A printing method includes the operation of supplying the above-described printing fluid through one or more narrow nozzles. The supply of printing fluid (s) is carried out through several narrow nozzles, the nozzles being individually controlled. or in groups regarding the presence or absence of a printing fluid supply. The nozzles individually or in a group are regulated with respect to the duration or intensity of the outflow of the printing fluid [RU 2312882 C09K1 1/08, C09D1 1/00, B41J2 / 00, B41MZ / 14 Publ. December 20, 2007, WO 03/052025 06/26/2003].

Analogues of the methods for producing ink with nanoparticles for color inkjet printing, which allow color interference images to be printed with colorless ink, formed by at least one xerogel refractive layer transparent in the visible region of the spectrum, were not found in the scope of the search.

The known sol-gel processes are known as the technology of materials, including nanomaterials, including the production of sol with its subsequent transfer to gel, that is, to a colloidal system consisting of a liquid dispersion medium enclosed in a spatial network formed connected particles of the dispersed phase. [L8: // sh. \ U1k1re (11a.og / 1k1 / Sol-gel_process].

Sol (plural sol, from Latin solutio — solution) is a highly dispersed colloidal system (colloidal solution) with a liquid (lyosol) or gaseous (aerosol) dispersion medium, in the volume of which another (dispersed) phase is distributed in the form of liquid droplets , gas bubbles or small solid particles, the size of which lies in the range from 1 to 100 nm [pnMr8: // gy. \ ¥ 1k1resNa.o ^ L ¥ 1k1 / Zoli].

Gels (unit gel, from nar.gelo - “freeze”) are structured systems consisting of high molecular weight and low molecular weight substances. The presence of a three-dimensional polymer skeleton (mesh) informs the gels of the mechanical properties of solids: lack of fluidity, ability to maintain shape, strength and deformability (ductility and elasticity) [https: / en.wikipedia.org/wiki/Γel].

In contrast to gels, in sols, the particles of the dispersed phase are not bound into the spatial structure, but freely participate in Brownian motion [Lir: // (11C. sucks 1s.g / o! 1s.p8 ^ papo1es11po1o y / 449 / Zol].

Most gels are known to be thermodynamically unstable; during aging due to isothermal recondensation or recrystallization, the coagulation structure that is reversible with respect to the mechanical action degenerates into an irreversible condensation-crystallization structure. In addition, many gels are prone to syneresis - volume reduction with the release of the liquid phase as a result of spontaneous compaction of the structural network [http://www.xumuk.ru/encyklopedia/958.html].

The general name “sol-gel process” (sol-gel technology, sol-gel method) ”unites a group of methods for obtaining (synthesis) of materials from solutions, the essential element of which is gel formation at one of the stages of the process.

The most famous variant of the sol-gel process is based on the processes of controlled hydrolysis of compounds, usually alkoxides M (OR) _x (M = Si, Ti, Zr, V, Zn, Al, Sn, Ge, Mo, W, etc.) or the corresponding chlorides, in an aqueous or organic, often alcoholic, environment [hereinafter https://ru.wikipedia.org/wiki Zol-gel_procecc].

At the first stage of the sol-gel process of the hydrolysis and polycondensation reaction lead to the formation of a colloidal solution - sol - particles of hydroxides, the size of which does not exceed several tens of nm.

An increase in the volume concentration of the dispersed phase or any other change in external conditions (pH, solvent replacement) leads to intensive formation of contacts between the particles and the formation of a monolithic gel in which the solvent molecules are enclosed in a flexible but sufficiently stable three-dimensional network formed by hydroxide particles.

The concentration of sols with subsequent gelation is carried out by dialysis, ultrafiltration, electrodialysis, evaporation at relatively low temperatures or extraction.

It is known that the processes of solvent removal from the gel (drying) play an extremely important role in the sol-gel process. Depending on the method of their implementation, various synthesis products (xerogels, ambigels, cryogels, aerogels) can be obtained.

Airgel is the common name for all gels with a low solids content, the pores of which are filled with air, in a narrower sense they are characterized by the fact that they are used in supercritical drying, in the preparation of cryogels, freeze-drying, and in the preparation of xerogels, convection subcritical drying .

Ambigel is a product of drying an aqueous or organic gel at atmospheric pressure, characterized, in contrast to xerogel, by low density values approaching the density of airgels ^

Xerogel (English xerogel) is a product of drying aqua or alkali gels at atmospheric pressure under conditions leading to the collapse (collapse) of macropores and a significant increase in the density of the material [http://thesaurus.rusnano.com/wiki/article2155].

Common features of these products are the preservation of nanoscale structural elements and fairly high values of specific surface area (hundreds of m ² / g), although their bulk density can differ hundreds of times.

Most sol-gel synthesis products are used as precursors in the preparation of oxide nanopowders, thin films for coating optical lenses or ceramics.

In dispersed systems, a double electric layer appears on the surface of particles (at the particle-dispersion medium interface) [http://www.photocor.ru/theory/zeta-potential/].

The double electric layer is a layer of ions, formed on the surface of a particle as a result of adsorption of ions from a solution or dissociation of surface compounds. The particle surface acquires a layer of ions of a certain sign, uniformly distributed over the surface and creating a surface charge on it.

Theories of the double electric layer are widely used to interpret surface phenomena, but there are no direct methods for measuring potentials at the boundary of the adsorption layer. To quantify the magnitude of the electric charge in the double electric layer, the zeta potential is widely used. The zeta potential is not equal to the adsorption potential or surface potential in the double electric layer. However, the zeta potential is often the only available way to evaluate the properties of a double electric layer.

When a particle moves, the double electric layer breaks.

The place of the gap when moving the solid and liquid phases relative to each other is called the slip plane. The slip plane lies on the boundary between the diffuse and adsorption layers, or in the diffuse layer near this boundary. The potential on the slip plane is called the electrokinetic or zeta potential (ζ potential).

In other words, the zeta potential is the potential difference between the dispersion medium and the fixed layer of liquid surrounding the particle [http://thesaurus.rusnano.com/wiki/article2155].

The importance of the zeta potential is that its value can be associated with the stability of colloidal dispersions. The zeta potential determines the degree and nature of the interaction between the particles of the dispersed system.

For molecules and particles that are small enough, a high zeta potential will mean stability, i.e. solution or dispersion will resistant to aggregation. When the zeta potential is low, attraction exceeds repulsion, and dispersion stability will be violated. So, colloids with a high zeta potential are electrically stabilized, while colloids with a low zeta potential tend to coagulate or flocculate.

A zeta potential value of 30 mV (positive or negative) can be considered as a characteristic value for the conditional separation of low-charged surfaces and high-charged surfaces. The greater the electrokinetic potential, the more stable the colloid.

It is known that at values of the zeta potential from 0 to ± 30 mV, poor stability of colloidal systems is observed (coagulation or flocculation is possible), and at values greater than ± 30 mV, good stability of colloidal systems [http://thesaurus.rusnano.com/wiki / article2155].

A known method of producing water dispersible nanoparticles of sols of titanium dioxide rutile phase rutile with an average particle diameter of less than 30 nm of high purity in an aqueous medium that does not have ionic impurities and is used for optical materials having a high refractive index and having a high dielectric constant and dispersibility in solvents without any any ionic impurities such as SG, NO ₃ ^" , S0 ₄ ^{" 2} , comprising the following steps: production of a mixed solvent from water and hydrogen peroxide; hydrolysis of titanate peroxide and hydrothermal treatment of the solution with dissolution of titanate peroxide and the formation of a titanium dioxide sol [US20061 10319 C01 G23 / 047 2006-05-25].

Analogs of sol-gel inks for color inkjet printing, which allow color interference images to be printed with colorless ink, formed by at least one refractive layer transparent in the visible region of the spectrum xerogel, in the scope of the search, was not found.

The closest prototype analogue in technical essence and technical result obtained is a method for producing a titanium oxide sol, comprising the steps of: a) increasing the temperature of the reagent solution containing the titanium oxide precursor as a solvent for the reaction to a reaction temperature of 70 to 95; b) obtaining a titanium oxide sol with the addition of an acid catalyst with a reagent solution and carrying out a sol-gel reaction while removing the solvent for the reaction from it; and c) drying the prepared sol by freeze-drying, normal pressure drying, or vacuum drying and re-dispersing the dried titanium in a dispersion solvent. The sol-gel reaction when removing the solvent for the reaction in step b) is carried out at a temperature of from 70 to 95 ° C. The solvent for the reaction and the solvent for dispersion is the same or different one or more solvents selected from the group consisting of water, a lower alcohol from C _G C ₅ , a higher alcohol C ₆ or more, ethylene glycol, and acetyl acetone. The lower alcohol is methanol, ethanol, propanol, isopropyl alcohol, butyl alcohol, or isobutyl alcohol or and the higher alcohol is polyvinyl alcohol. The titanium oxide precursor is one or more compounds selected from the group consisting of titanium, tetraethoxysilane tetraisopropoxy titanium, titanium tetrabutoxy zirconium, titanyl chloride, titanyl sulfate and oxytitanyl sulfate. An acid catalyst is one or more compounds selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, and acetic acid. The acid catalyst is added in an amount of from 1 1 to 30 parts by weight based on 100 parts by weight of the titanium oxide precursor. One or more inorganic salts selected from the group consisting of NaCl, KCl, NaBr and KBr, or one or more surfactants selected from of the group consisting of sodium dodecyl sulfate, cetyltrimethyl ammonium bromide and cetyl trimethyl ammonium chloride are added to the reagent solution in step a) in an amount of 1 to 10 parts by weight, based on 100 parts by weight of the titanium oxide precursor. Primary particles of titanium dioxide having an average diameter of from 1 to 200 nm in the crystalline form of anatase or rutile. Secondary titanium dioxide particles have an average diameter of 200 nm or less. The titanium dioxide sol has a solids content of May 8 to 50. % The composition for coating glasses, industrial safety glasses or leisure glasses contains a sol of titanium dioxide in an amount from May 10 to May 70. % [WO2007073043 2007-06-28 C01G23 / 047 prototype].

The technology for producing sols of crystalline titanium dioxide nanoparticles according to the prototype WO2007073043 involves the implementation of multi-stage operations aimed at obtaining functional sol-gel powder and film materials. The steps for preparing the powder include hydrolysis followed by protonization and further precipitation using drying. At the same time, the values of the refractive index obtained in the prototype, not exceeding 1.6, make it possible to concentrate the field of application of the coatings obtained on the basis of T ₂ nanocrystalline sols solely as antireflective (i.e., bleaching!) And UV protective layers for glasses for various functional purposes.

However, the technology of the prototype WO2007073043 does not allow obtaining sedimentation-resistant sols (colloids) based on crystalline titanium dioxide without using the stage of complete dehydration or drying. This, in turn, does not allow to achieve high values of the refractive index (more than 1.7) in the entire visible range even after the introduction of a volatile solvent and, therefore, does not allow the formation of color interference nanostructures.

SUMMARY OF THE INVENTION

The main objective of the invention is to enable inkjet printing of color interference images on non-porous surfaces by means of specially prepared colorless sol-gel inks with the ability to observe color images in reflected light of the visible spectrum, which in itself is especially unique to the inkjet printing method.

The technical results obtained by the implementation and use of the invention are:

- the formation by inkjet printing of optical film nanostructures from nanocrystalline sols of titanium dioxide with an accuracy of 10 nm, which provide the appearance of controlled interference, while usually inkjet printing focuses on micrometer manipulation of printed objects, and only in exceptional cases goes into the nanoscale;

- the creation of non-toxic inkjet inks based on chemically inert titanium dioxide, while classic inkjet colors are environmentally hazardous and include the use of toxic compounds such as Cd ²⁺ for a yellow cartridge;

- obtaining ink for inkjet printing that does not fade from the action of sunlight and UV radiation of interference-colored images that have high adhesion to a non-porous substrate;

- providing the possibility of re-application of ink for inkjet printing of refractive layers and reuse of the substrate with the ability to remove the applied layers with aqueous solvents. A characteristic distinctive original feature of the invention is the use of inkjet printing technology to create color interference nanolayers of xerogel layers of nanocrystalline titanium dioxide with high accuracy without the use of high temperatures and technically complex physical processes.

This was made possible thanks to the creation of a technology for the production of special sol-gel inks based on a nanocrystalline sol of titanium dioxide of a predominantly anatase phase, during the natural drying of which optically monolithic coatings are formed in the form of a refractory xerogel layer of nanocrystalline titanium dioxide with a high refractive index (more than 2 in the entire range of visible light )

Controlling the thickness of the xerogel refractory layer of nanocrystalline titanium dioxide with an accuracy of 10 nm by means of a jet application of sol-gel ink allows to obtain color images in the entire color range of the visible light spectrum with controlled interference using only colorless ink.

The absence of dyes in the proposed sol-gel inks for color inkjet printing is highly promising from an environmental perspective, since the systems used based on nanocrystalline anatase titanium dioxide sols are non-toxic and bioinert.

According to the invention, a fundamentally new method for preparing sol-gel colorless inks for color interference inkjet printing is proposed for creating color interference images by inkjet printing, which makes it possible to create refractive coatings with a given thickness with an accuracy of 10 nm, necessary to create color interference images even on unprepared smooth polymer films.

The proposed approach lays the foundation for the development of a fundamentally new direction in color interference inkjet printing and allows one to master new methods of forming optical nano-objects with an accuracy of 10 nm using widely available inkjet printing methods using conventional inkjet printers on non-porous smooth substrates.

The problem is solved and the required technical result is achieved by the fact that according to the invention receive sol-gel ink for color interference inkjet printing containing nanocrystalline sol of titanium dioxide predominantly anatase phase in a solution of ethyl alcohol in water, characterized by at least one of the following properties:

the presence of titanium dioxide nanoparticles in the form of crystals of titanium dioxide of a predominantly anatase phase with a content of an amorphous phase of titanium dioxide of not more than 5%,

the concentration of nanocrystalline particles of titanium dioxide on May 1-5. %

the size of the nanocrystalline particles of titanium dioxide 5-200 nm, the average hydrodynamic diameter of the particles of the nanocrystalline sol of titanium dioxide is not more than 200 nm, mainly 15.8 nm,

the zeta potential of titanium dioxide nanoparticles is not less than +30 mV, mainly +36 ± 5 mV,

the possibility of forming a transparent in the visible spectrum of the refractive layer of the xerogel of titanium dioxide with a thickness of 300 nm to 1000 nm with a refractive index of more than 1.7,

the concentration of ethyl alcohol in water no more than 70 may. % with a predominant ratio of ethyl alcohol: water 3: 1, viscosity not more than 2.5 mPa * s, mainly 2, 1 mPa * s, surface tension not more than 30 nN / m, mainly 27 nN / m

the duration of sedimentation stability of the nanocrystalline sol of titanium dioxide for at least 1 year.

Sol-gel ink for color interference inkjet printing containing nanocrystalline sol of titanium dioxide in a solution of ethyl alcohol in water, according to the invention, is obtained in two stages:

at the first stage receive a nanocrystalline sol of titanium dioxide predominantly anatase phase in water,

and in the second stage, a sol-gel ink for color interference inkjet printing in the form of a nanocrystalline titanium dioxide sol in a solution of ethyl alcohol in water is obtained from a nanocrystalline sol of titanium dioxide of a predominantly anatase phase in water, with the density, viscosity and surface tension required for inkjet printing.

A nanocrystalline sol of titanium dioxide of a predominantly anatase phase in water is obtained by:

obtaining a solution of titanium alkoxide by mixing titanium isopropoxide and 2-propanol,

hydrolysis of guitar alkoxide with the formation of stable crystalline nuclei of anatase titanium oxide in water,

conducting temperature dehydration of amorphous titanium oxyhydroxide by heating to 70 ° C in an acidic environment,

the creation of an acidic medium and holding at 80 ° C for 1 hour with an increase in the content of the crystalline phase of the anatase phase titanium oxide and obtaining a nanocrystalline titanium dioxide sol of a predominantly anatase phase with a titanium dioxide crystal size of not more than 200 nm, mainly 5-200 nm, with average hydrodynamic diameter of sol particles no more than 30 nm predominantly 15.8 nm, with a zeta potential of sol particles of at least +30 mV, predominantly +36 ± 5 mV,

stabilization of the nanocrystalline sol of titanium dioxide predominantly anatase phase by protonization of the sol particles in the presence of nitric acid and holding for 1-2 weeks at room temperature with constant stirring to obtain a stable nanocrystalline sol of titanium dioxide predominantly anatase phase with a content of the amorphous phase of titanium dioxide not more than 5% with a titanium dioxide crystal size of 5-200 nm, mainly of the anatase phase, with an average hydrodynamic diameter of the sol particles of not more than 200 nm predominantly 15.8 nm, with a zeta potential of sol particles of at least +30 mV, mainly + 36.1 + 5.3 mV.

Sol-gel ink for color interference inkjet printing in the form of a nanocrystalline sol of titanium dioxide in a solution of ethyl alcohol in water is obtained by:

bringing the viscosity parameter of a nanocrystalline sol of titanium dioxide of a predominantly anatase phase in water to an index of not more than 2.1 MPa * s by concentrating a sol of nanoparticles of titanium dioxide of a predominantly anatase phase in water to a concentration of not less than May 8. % by vacuum evaporation at a temperature of 50 ° C,

obtaining the required density and surface tension of the nanocrystalline sol of titanium dioxide predominantly anatase phase of not more than 25 mN / m by adding ethanol to a concentration of ethyl alcohol in water of not more than 70 mass. %

ensuring phase equilibrium between water and ethanol by homogenization for at least 12 days to obtain a nanocrystalline sol of titanium dioxide predominantly anatase in a solution of ethyl alcohol in water, characterized by at least one of the following group of properties:

the presence of nanocrystalline particles of titanium dioxide in the form crystals of titanium dioxide predominantly anatase phase with a content of an amorphous phase of titanium dioxide of not more than 5%,

the size of the nanocrystalline particles of titanium dioxide 5-200 nm, the average hydrodynamic diameter of the sol particles is not more than 20 nm, mainly 15.8 nm,

the zeta potential of sol particles is not less than +30 mV, mainly

+36 ± 5 mV mV,

the possibility of forming a nanocrystalline titanium dioxide transparent xerogel refractory xerogel layer visible in the visible spectrum with a thickness of 300 nm to 1 μm with a refractive index of more than 1.7, and a concentration of ethyl alcohol in water of not more than 70 mass. % with a predominant volume ratio of ethyl alcohol: water 3: 1,

viscosity not more than 2.5 MPa * s, mainly 2, 1 MPa * s, surface tension not more than 30 nN / m, mainly 27 nN / m.

In color interference printing with the solgel ink described above, at least one xerogel layer of a nanocrystalline titanium dioxide predominantly anatase phase xerogel transparent with a thickness from 300 nm to 1 μm is formed on a substrate on a substrate,

about with a refractive index of more than 1, 7, mainly more than 2,

o with varying color depending on the thickness of the refractive layer

The formation of the xerogel refractory layer of nanocrystalline titanium dioxide of a predominantly anatase phase is carried out by means of a sol-gel ink in the form of a nanocrystalline titanium dioxide sol, in a solution of ethyl alcohol in water by inkjet printing, rolling, spraying or dipping.

The color management of images printed in detail by the above-described sol-gel ink in the form of nanocrystalline titanium dioxide of predominantly anatase form is carried out by forming a predetermined thickness of the refractive layer of nanocrystalline titanium dioxide of predominantly anatase form by:

layer-by-layer application of sol-gel ink to a predetermined xerogel refractive layer thickness,

a change in the concentration of the solid phase in the sol-gel ink, using a set of sol-gel inks with a given concentration to form a certain thickness of the refractive layer of titanium xerogel dioxide with a certain color

As a result of color inkjet printing with the above-described sol-gel ink, nanocrystalline particles of predominantly anatase titanium dioxide produce a printed product with a color interference image on the surface containing at least one refractive layer of at least one xerogel layer of nanocrystalline titanium dioxide predominantly anatase phase with the thickness of the refractive layer from 300 nm to 1 μm, with a refractive index of the refractive layer of more than 1.7 and with a varying color depending on the thickness of the refractory xerogel layer of nanocrystalline titanium dioxide.

Printed products with a color interference image are not obtained on a non-porous smooth or polished surface with a minimal change in texture height along the z axis, for example, on a polyethylene (PET) film, on a surface resistant to ethyl alcohol and liquids with a pH value of at least 3, on the surface, containing water-insoluble substrates on an opaque surface or a surface containing Bragg mirror coatings with preservation of a color rendition not less than 1 year.

Brief Description of the Drawings

In FIG. 1, 2, 3 show examples of color images printed on an inkjet printer, obtained as a result of interference in nanocrystalline titanium dioxide xerogel thin films by sol-gel ink obtained by the proposed method. The implementation of the invention

In contrast to the known methods for creating an interference effect on solid materials, that is, the formation of thin-film refractive structures with a modified refractive index, which are usually realized using technically complex physical (laser, temperature or vacuum) exposure, the invention is based on the methods of solution chemistry.

The proposed method allows to obtain obtaining sol-gel ink for color inkjet printing using solution chemistry methods that allow you to create thin (5-10 nm thick) interference refractive layers of environmentally friendly and biologically inert inorganic material (xerogel nanocrystalline anatase titanium dioxide), which after application two conditions are mandatory for observing the phenomena of interference on the substrate, namely, obtaining a refractive index above 1.7, i.e., a higher in simple polymer (1.5), and the refractive forming layer after drying with a predetermined thickness nanoscale, complementary light wavelength of the visible spectrum from 300 nm to 1 micron up to 10 nm.

Moreover, in contrast to the well-known highly refractive organic polymers, the viscosity parameter in the resulting sol-gel Ink can be set up in a relatively simple way by controlling the gelation stage. Moreover, in the case of a high degree of chemical protonization of the surface of the sol nanoparticles, the viscosity will be determined mainly by the concentration of the solvent (mainly ethanol), while sedimentation of the nanocrystalline particles of the sol of titanium dioxide in this case is excluded.

The rheological properties required for inkjet printing of the obtained sol-gel ink are adjusted by controlling the phase sol-gel transition and introducing volatile solvents, mainly ethyl alcohol (hereinafter, ethanol), into the composition of the sol-gel ink.

It is this advantage of the obtained sol-gel ink that makes them unique for use as a material for creating environmentally friendly color interference inkjet printing.

Obtained by the proposed technology, color interference printing products have unique properties, such as the absence of color change over time, which is promising for long-term storage of color images, since the main material (nanocrystalline titanium dioxide) is extremely stable, inert and does not decompose for a long time even under the influence of UV radiation.

Inkjet printing with the resulting highly refractive sol-gel inks allows the use of polymer substrates without first modifying and applying the binder layers that are commonly used in inkjet printing.

Considering the ability of many inorganic sols (colloids) to resuspend, the proposed printing technology is universal and can be reused when re-applying the image to a polymer substrate or to a previously made image.

Among the many inorganic colloids that can be adapt to inkjet printing and actively use it now, only a few can be attributed to highly refractive, with high transparency and not expensive to use, for example, ZrO ₂ , Ti0 ₂ , ZnO, FeO.

A common property of these oxides is the ability to form transparent layers in the visible region of light with a high refractive index, greater than 1.5.

For other inorganic compounds, there are problems with the stability of their sols due to the occurrence of spontaneous gelling, the absence of UV absorption (which is important for the high stability of printed images) and insufficient adhesive properties.

The most preferred of these is titanium dioxide TU ₂ , for the following reasons:

- the preparation of crystalline sol-gel systems of titanium dioxide is quite well understood,

- the refractive index of titanium dioxide in the anatase phase is

2.61,

- the xerogel of nanocrystalline titanium dioxide is completely transparent in the visible region and in the UV region and has an increased refractive index (more than 2),

- titanium dioxide easily crystallizes under conditions of temperature dehydration, since it almost always has a crystalline core,

- a high value of the isoelectric point (I.E.P. = 5.9) allows to obtain highly stable, sedimentation-resistant sols of titanium dioxide,

- titanium dioxide is characterized by a phase sol-gel transition.

As the studies of the authors have shown, for the synthesis of nanocrystalline particles of Ti ₂ predominantly anatase phase from titanium alkoxides, titanium isopropylate is most preferred, which forms stable crystalline nuclei during hydrolysis. The stage of ash formation, that is, the formation of a dispersed solid phase, includes successively the stages of hydrolysis and condensation as a mechanism for the formation and growth of nanoparticles.

Schematically, the interaction of alcoholates with water (hydrolysis reaction) can be represented as follows (where R is an alkoxide radical, for example C ₃ H ₇ 0):

= Ti-OR + H ₂ 0 -> = Ti-OH + R- (OH)

ΞΊΪ-ΟΗ + RO-Ti -> = Ti-0-Ti ^ R- (OH)

The use of titanium isopropylate as an inorganic precursor has several significant advantages. One of the most important is the possibility of stepwise hydrolysis, due to the regulation of synthesis conditions.

15 s ₃ n ₇ about he

Ti (C ₃ H ₇ 0) ₄ + H ₂ 0—>^' + C ₃ H ₇ OH

s ₃ n ₇ o s ₃ n ₇ o

or

with ₃ n ₇ about he

²⁰ Ti (C ₃ H ₇ 0) ₄ + - +2 C ₃ H ₇ OH

with ₃ n ₇ about ^he

Due to the high reactivity of such a precursor, its use is carried out with the addition of various organic 2 _< . modifiers to prevent aggregation processes.

In this particular case, aggregation was prevented by protonating the surface of titanium dioxide nanoparticles with the addition of nitric acid.

After hydrolysis, the formation of sols is responsible for the condensation mechanisms. They proceed according to the following reactions: a) alkoxylation:

ΞΤΪ -OH + iC ₃ H ₇ O ~ Τι = -> = Τι -О- Ti = + iC ₃ H ₇ OH

b) oxidation:

c) olation:

N ΞΤί

ΞΤΐ-ΟΗ + SQ / - \ O-HE + iC ₃ H ₇ OH iC ₃ H ₇ /

The key role in further structuring is played by polycondensation processes that promote the formation of hybrid bonds and the formation of ordered structures in the form of a gel array, i.e. according to the principle of gelation:

Dehydrated Polycondensation:

from ₃ n ₇ o he is from ₃ n ₇ o s ₃ n ₇ o o _h . from ₃ n ₇ o

+ \ ^B ₊ H ₂ (C ₃ H ₇ o / \ C ₃ H ₇ C ₃ H ₇ on / \ _r ^with s _u H _7n about _SzN7 o / \ o ^H r zNn or ₇ ou

2H ₂ 0

Depropanol floor condensation:

The frequency of such structures substantially depends on many parameters and synthesis conditions. The formation of such bond bridges determines the presence of nanostructures in such materials and their final properties, causing the occurrence of the sol-gel transition in the TU ₂ system.

The gel formation stage for interference inkjet printing by the proposed sol-gel inks proceeds directly on the substrate, since the main condition for gel formation is an increase in the density of the coagulation contact, which is achieved by the natural removal of a volatile solvent, mainly ethanol. Otherwise, gelling may occur inside the ink cartridge, which is unacceptable for ink jet stability.

Sol-gel ink for color interference inkjet printing in the form of a nanocrystalline sol of titanium dioxide, in a solution of ethyl alcohol in water is prepared in two stages,

and at the second stage, a sol-gel ink for color interference inkjet printing in the form of a nanocrystalline titanium dioxide sol in a solution of ethyl alcohol in water is obtained from a nanocrystalline titanium dioxide sol of a predominantly anatase form in water, with the density, viscosity and surface tension required for inkjet printing.

To prepare a nanocrystalline sol of titanium dioxide in water, two solutions are first prepared:

For the first solution, 3-16 ml of titanium isopropoxide and 12-50 ml of 2-propanol. This concentration ensures the solids content in the resulting sol-gel ink at the level of May 1-5. %

To prepare a second solution, 0.7- 2.4 ml of nitric acid is added to 100 ml of water and the mixture is heated to 70 ° C to initiate the process of temperature dehydration and increase the content of the crystalline phase, after which the first is gradually added to the second solution with stirring.

The introduction of acid promotes a change in the pH of the solution, which is responsible for the process of crystal formation and an increase in the ionic strength of the solution, contributing to an increase in the mobility of the molecules and accelerate the dissolution of the molecular "coat" of ligands and ions of crystalline Ti0 ₂ nuclei. As a result, the degree of protonization of the particle surface increases to a zeta potential of at least +36 ± 5 mV, which ensures high stability of colloidal particles and leads to the required size of the formed crystalline formations of titanium dioxide at a level of about 5-200 nm, mainly of the anatase phase.

The resulting mixture was incubated for 1 hour at a temperature of 80 ° C, after which it was sealed with a film and incubated for 1-2 weeks at room temperature with stirring.

Long exposure helps to achieve equilibrium of the colloidal system of the sol and a gradual increase in the content of the crystalline phase to an indicator of at least 95% relative to the solid phase.

The resulting solution of nanocrystalline sol of titanium dioxide in water does not meet the criteria for inkjet printing, such as density, viscosity and surface tension, in its rheological parameters, therefore, at the second stage of the sol-gel ink preparation for interference inkjet printing, the nanocrystalline sol of titanium dioxide in water is modified with a volatile solvent, mainly ethyl alcohol (ethanol).

The predominant choice of ethanol as a volatile solvent is due to its low surface tension, economic cheapness and affordability, the ability to pre-solvate in water without destroying the double electric layer of micelles of the synthesized nanocrystalline sol of titanium dioxide.

To obtain the viscosity index required for inkjet printing, the synthesized sol of titanium dioxide is first concentrated by evaporation in a rotary evaporator under pressure at 50 ° C to bring the concentration of solid phase TU ₂ to a concentration of at least 8 mass. % This is necessary to bring the viscosity parameter of the finished sol-gel ink to a level of at least 2.1 MPa * s, in order to ensure the possibility of squeezing a drop of ink from the nozzle of the print head of an inkjet printer.

To obtain the surface tension required for inkjet printing, sol-gel ink, an aqueous solution of sols of nanocrystalline titanium dioxide is mixed with ethanol, mainly the following stoichiometry of H ₂ O / Ethanol 1: 3.

This stoichiometry determines the set of required density and surface tension of at least 25 mN / m.

The resulting solution is homogenized for at least 12 days to achieve phase equilibrium between the solvents.

The main rheological characteristics of the sol-gel ink depending on the ethanol content are presented in Table 1, where the Z parameter was calculated based on the equation: Z = V (d-σ-δ) / η, where δ is the density, d is the nozzle diameter, and σ is surface tension, η - viscosity. Table 1

The rheological characteristics of sol-gel ink depending on

ethanol content (ethanol)

These data show that the most optimal for inkjet printing according to the dependence of the sol-gel ink parameters on the concentration of ethanol and the crystalline ash of titanium dioxide of the predominant anatase phase are sol-gel inks containing 70 May. % ethanol.

It was also established that the stability of the nanocris ι allic sol of titanium dioxide of a predominantly anatase phase sharply decreases with the addition of ethanol over May 70. %

This is due to the fact that ethanol changes the structure of the double electric layer of Ti ₂ particles, drastically lowering their stability.

Inkjet printing with sol-gel ink can be carried out on virtually any surface of any material that meets the conditions of inkjet printing, however, to obtain thin interfering layers, the substrate must meet the following basic conditions: have a non-porous, mostly smooth or polished surface with a minimal change in the height of the texture along the z axis,

be resistant to ethanol and liquids with a ph value of at least 3,

contain water-insoluble substrates.

Titanium dioxide anatase nanoparticles formed during the preparation of sol-gel ink inks have a purely crystalline structure, with an average crystallite size of about 5 nm, which corresponds to the direction of the interlayer distance of the body-centered tetragonal anatase structure.

A nanocrystalline lattice of TiO ₂ particles is extremely important for obtaining interference in thin films, as already noted.

The high-resolution transmission electron microscopy (HRTEM) data obtained by the authors confirm the presence of a single crystalline phase with a high degree of crystallinity.

The x-ray diffraction data of the synthesized TU ₂ particles obtained by the authors show diffraction peaks at angles 25.411 (101), 37.911 (004), 48.011 (200), 54.011 (105), 54.911 (211) and 62.811 (204), which also confirms the anatase TU ₂ phase with an average crystallite size of no more than 5, calculated by the Scherrer equation. These data are completely consistent with the data of transmission electron microscopy and electron diffraction.

For printing thin interference layers, the uniformity of the refractive film is critical to product reliability, and inks containing stabilized colloidal nanoparticles are necessary for the liquid phase deposition of thin films. For oxide particles, surfactants are most often used to stabilize colloidal ink. However, the addition of surfactants or polymers leads to a significant loss of optical properties and stability for TU ₂ printing films. In the study, a simple pH control approach was used to protonize the surface and increase the stability of sol particles in order to achieve high homogeneity of the formed layers. The protonization of the surface of the sol particles significantly shifts the critical point of gelation, preventing the development of coagulation contact between the particles.

As a result, structure formation by the polycondensation mechanism begins to occur when the interaction force is 10 ^" " -10 ^"10 n / contact, when the distance between the particles decreases to 10 ^{~ 9} m.

This approach can significantly reduce the diameter of the nozzle while maintaining high stability of inkjet printing. Thus, the production of stable TU ₂ sol-gel inks should occur in the pH range between 2 and 5.

The zeta potential of TU ₂ nanocrystalline particles in sol-gel ink is predominantly +36 mV, which ensures a stable state of the sol.

To increase the crystallinity of the sol particles and the corresponding increase in the refractive index of the solid phase, the ionic strength of the solution was increased by introducing a compound with a high dissociation constant in the form of inorganic nitric acid (K _a = 24).

Considering that the protonating agent is capable of influencing the phase composition of Ti ₂ during crystallization of amorphous sol particles, this choice was due to the ability of nitric acid to contribute to the formation of the most photoactive phase of anatase.

The most popular polymorphic modifications (phases) of TU ₂ - rutile, anatase and brookite have close refractive index values, but the advantage of producing anatase is determined by using a pH closer to neutral, thus minimizing the effect of corrosion processes in the print.

The presence of a volatile solvent (mainly ethanol) in sol-gel ink promotes quick drying of ink on a film.

Ethanol plays a very important role, because it is the main factor affecting the rate of evaporation of the solvent from the ink. A low concentration of ethanol can contribute to slow drying of the ink on the substrate, coalescence, and an unpredictable change in morphology, while an excess concentration of ethanol leads to a decrease in particle stability due to the destruction of the double isoelectric layer.

For control experiments, we used the widespread Canon Pixma IP2870 desktop printer, with standard cartridges PG745, CL-746.

The print head integrated in the cartridge had a droplet size of 2 PL and a nozzle diameter of 1.280 μm.

After washing, the cartridge was filled with TU _{2 with} prepared sol-gel ink, without any further modification.

No design changes were made to the design of the printer and cartridge.

Viscosity was determined with a Brookfield HA / HB viscometer, and surface tension with a Kyowa DY-700 tensiometer.

To control the color of the image obtained after drying the sol of the refractive layer of the xerogel of titanium dioxide, it is necessary to form even homogeneous layers in order to achieve the interfering effect in solid thin films.

To study the relief of the deposited structures, atomic force microscopy (AFM) was used to scan the surface relief.

According to the data obtained by the authors of the profilogram of AFM images, it was found that the change in relief, regardless of the number of layers applied, changes by no more than 200 nm in the range up to 1 μm. Such a surface fully provides conditions the occurrence of interest in thin films of xerogel titanium dioxide and can be used for color printing technology using the inkjet method of optical nanostructures.

The change in surface topography is associated with a small particle size, which, according to the TEMP and SEM data, predominantly has a size of 1-5 nm and does not exceed 10-15 nm.

This proves that sol-gel inkjet printing based on a nanocrystalline sol of titanium dioxide predominantly of the anatase phase in an aqueous solution of ethyl alcohol is easily achievable with the high accuracy necessary for constructing the interfering layers of individual elements of color interference images.

It is known that in order to obtain images by means of inkjet printing on a PET film, it is usually preheated to 70 ° C to increase the drying speed of the ink, but the use of volatile ethanol additive in the sol-gel inks used according to the invention does not require this, despite the fact that the speed evaporation below 70 ° C.

The solvent removal gradient of the proposed and used sol-gel inks allows one to obtain a dense uniform transparent film highly refractive about xerogel titanium dioxide.

According to SEM, the nanoparticles of the resulting titanium dioxide xerogel are spherical aggregates of predominantly 5-10 nm in diameter, densely packed together.

The results of profilometric analysis show that the film has a curved surface with a slight roughness, which indicates the high compactness of the aggregated nanoparticles forming the layers during slow drying. A more detailed analysis of the surface texture provides AFM images for different layers shows that the superposition of the layers does not lead to a change in the surface structure due to the "healing" of defects of the previous layer with a newly filled sol. The continuity of the layers confirms the absence of surface cracking, which can occur during quick drying of the layers and uneven application of the material to the surface, which is in good agreement with classical methods of application.

To determine the correspondence to the determined thicknesses of the xerogel layer of titanium dioxide from the reflection spectra, scanning electron microscopy of ultrahigh resolution (SEM - HC) was used.

For this, the substrate was subjected to a perpendicular cut in the direction of movement of the print head. To determine the TU ₂ interface subinterface, in order to determine the true thickness of the xerogel layer of titanium dioxide, we used energy dispersive analysis with a color contrast function.

As a result, the formation of even layers of titanium dioxide xerogel close to perfect condition was observed, which indicates the impeccability of the printing technology and the sol-gel ink composition used.

According to the data obtained by the authors, a high uniformity in the thickness of the xerogel of titanium dioxide and consistency between different measurements is achieved. In addition, it was found that the thickness of the xerogel layers of titanium dioxide is the same along the perimeter, regardless of the number of applications. It is also clearly seen that the obtained titanium dioxide layers have close contact with the surface of the substrate. This is due to the occurrence of a sol-gel transition of TU ₂ ink during drying and condensation of the sol into a dense xerogel layer. The particle size of the xerogel of titanium dioxide, not exceeding 200 nm, allows the deposition of the proposed sol-gel ink with high penetration.

The study of the mechanical properties of jet coatings of xerogel titanium dioxide on the surface of plastic films was performed using a texture analyzer.

It is known that the microhardness of xerogel films deposited from solutions is a key indicator, since the use of soft solution chemistry usually leads to a loss of mechanical resistance due to the formation of a high porosity of the xerogel layer.

In addition, inkjet printing on such non-porous surfaces, such as glass and polymers, causes a number of difficulties not only due to the coalescence of the droplets, but also due to the low adhesion of the dry xerogel layer to the glass and polymer substrate.

Studies have shown a decrease in mechanical strength by 2 times

(for the 7th layer relative to the first one), which may be due to the relatively low density of contact between the xerogel particles themselves after drying of the sol, and, as a result, a decrease in the mechanical hardness gradient with increasing thickness of the xerogel layer.

It is also known that layer-by-layer deposition of a sol can cause deformation of previous layers, complicating the process of obtaining hierarchical structures, therefore, to increase the mechanical strength of xerogels, heat treatment is used at 300-500 ° C, increasing the degree of crystallinity and initiating the occurrence of interfacial interactions with subsequent sintering.

Obviously, the effect of such high temperatures makes it impossible to deposit layers of an aqueous sol of titanium dioxide deposited by conventional methods on polymer substrates. The use of the inventive sol-gel inkjet ink in the form of a nanocrystalline sol of titanium dioxide of a predominantly anatase phase in a solution of ethyl alcohol in water makes it possible to obtain thin xerogel layers from the sol with regulation of thickness up to 10th at room temperature with strong bonding of individual xerogel layers to each other with a friend.

Full-color studies of color inkjet printing The interference images obtained by sol-gel inks showed that despite the structural features of titanium dioxide xerogel layers formed by wet solution chemistry, their optical properties turned out to be similar to the optical properties of calcined titanium dioxide xerogels.

Synthesized sol-gel inks can be classified as promising highly refractive coatings, given that in the entire visible range this refractive index does not fall below 1.85, which, given the high uniformity of deposition during the sol-gel transition, indicates the prospects of their use as real substitutes for organic refractive polymers .

Inkjet printing was carried out in a multi-pass technique. Each layer was completely dried after printing, so that the next layer was applied on a wet-to-dry basis.

The formation of an interference color image occurs in the process of condensation of the sol-gel ink on the surface of the substrate in xerogel. Evaporation of the solvent and gelation of the nanocrystalline sol of titanium dioxide with the formation of the specified thickness of the xerogel layer of titanium dioxide provides the ability to control the color of the printed image as a result of controlled interference.

Field studies have shown the practical possibility of forming an interference color image with the complete exclusion of temperature heating of the substrate for fixing the ink, which positively affects the preservation of the morphology of the applied layer and significantly reduces warping of the substrate after drying of the ink.

The relatively low concentration of the solid phase of nanocrystalline titanium dioxide in sol-gel inks allows for highly accurate positioning of xerogel nanostructures titanium dioxide with a high refractive index.

The color interference images printed by the inkjet method using sol-gel inks had a multi-color color with a high degree of detail (see Figs. 1,2, 3).

The appearance of color is caused by the appearance of reflected light waves formed at the phase boundary of two materials with different refractive index TU ₂ / air and TU ₂ / polyethylene. Interfering with each other, they form a light wave complementary to the thickness of the layer that caused this phenomenon.

Thus, the appearance of a color cast is associated with the thickness of the applied xerogel layer of titanium dioxide, which in the present invention can be controlled by the number of layers applied.

Practically implementing the invention for the first time it was possible to obtain a color image using colorless ink on an inkjet printer.

When using the obtained colorless sol-gel ink for inkjet printing and using the proposed method of color interference inkjet printing, almost any color image painted in the entire visible range of light can be obtained. Examples are presented in FIG. 1, 2, 3.

The uniqueness of the obtained sol-gel ink containing a nanocrystalline sol of titanium dioxide of a predominantly anatase phase, the availability of the starting materials for obtaining the sol-gel ink, and the niceness of the interference images obtained by the new method lies in the possibility of using the colorless sol-gel ink obtained for color interference printing and conventional inexpensive desktop inkjet printer.

The ability to adjust the rheological properties of the nanocrystalline sol of titanium dioxide and control its sol-gel transition to xerogel provides a wide range of variation properties necessary to obtain a sol-gel ink with the desired properties.

A nanocrystalline sol of titanium dioxide of a predominantly anatase phase, with an amorphous phase content of less than 5%, provides a manifestation of unique optical properties.

The condensation of xegogel titanium dioxide and its physical crosslinking with the surface of an unmodified PET film contributes to the excellent adhesion of xegogel titanium dioxide to the surface of a smooth substrate.

All this allows inkjet printing to produce unique color interference images with controlled color rendering on flexible and smooth polymer surfaces without the use of high-temperature heat treatment.

The uniqueness of the results lies in the practical ability to control inkjet interference printing, forming nanostructures of interference color images with high accuracy.

This was achieved only as a result of creating a fundamentally new approach to creating sol-gel ink and fixing sol-gel ink for inkjet printing on a non-porous polymer substrate, as well as by a new method for the synthesis of nanocrystalline sols of titanium dioxide predominantly anatase phase.

The protonization of the surface of the particles of nanocrystalline sols of titanium dioxide increases the stability of the ink and the shift of the phase sol-gel transition during atmospheric drying.

As a result, scalable optical interference nanostructures were first obtained by inkjet printing.

This is the basis for the use of soft solution chemistry when creating objects of quantum communication and an effective platform for the transport of photons in the future. The high precision of application and the unique optical characteristics of the obtained titanium dioxide xerogel layers of a predominantly anatase phase can be the basis for the production of planar waveguides, masking of microembedded paper, as well as the formation of a wide-angle photoinduced panel as the basis for creating a photon / signal supercomputer.

A characteristic distinctive original feature of the invention is the use of nanocrystalline sol-gel systems to create controlled interference in thin films using colorless ink based on nanocrystalline titanium dioxide sols.

The controlled multilayer printing of highly refractive layers of titanium dioxide xerogel allows the creation of optically transparent nanostructures on the surface of polymers, which interfering with interaction with visible light lead to visual staining of images.

The presence of a highly refractive layer or xerogel layers of titanium dioxide between air and the polymer substrate allows one to isolate monochromatic light reflections complementary in wavelength with the thickness of this layer.

Considering the multiple number of colors in the visible light spectrum, the color of the interference images created by the inkjet printer can be almost any.

The unique optical, morphological, and textural properties of the interference thin layers of titanium dioxide xerogel make it possible to put this into practice.

In this regard, the invention not only contributes to the creation of new color printing technologies, but also preserves the ecology of the environment and human health, protecting our planet. To increase the color contrast, the substrate may be opaque or contain coatings such as a Bragg mirror.

For inkjet printing of color images, the proposed method used a polyethylene (PET) film of A4 format, 1.5 μηι thick.

Image contrast was achieved using black film.

Color inkjet printing was carried out from a conventional black ink cartridge into which the resulting colorless sol-gel ink was preliminarily poured.

To print color images using the three-pass method, the settings used increased print quality, providing a twofold increase in ink.

To analyze the structure of the layers, we used inkjet printing with medium quality, which ensures the application of highly refractive layers with increased accuracy, but with less ink applied.

Printing was carried out by specially prepared files with masking areas.

Using a set of differently colored inks for inkjet printing is one of the main known methods for forming color images. Typically, ink color formation is achieved by combining CMYK or RGB colors.

According to the invention, a new technology for inkjet color printing using one of the proposed colorless sol-gel inks, is completely safe for use.

At the same time, the obtained sol-based ink significantly expands the possible choice of substrates for application, including the use of flexible polymeric substrates and smooth solids, which makes application in a format practically unlimited, and significantly facilitates the technology of application of interference structures controlled with an accuracy of 10 nm.

As the printed product may be packaging materials, tags, bags or other printed materials known in the art. The substrate may be any material that is used in the printing industry as a substrate. Substrates may include polymer films and other polymeric materials, various types of paper, ranging from thin tissue paper to corrugated cardboard, kraft paper, coated folders.

Metallic films and metal foils can also be used as a substrate.

The main substrate may be coated with preparations known in the printing industry to obtain a printed artistic image.

The printed product may receive a protective and decorative finish after the artistic image is printed on the substrate. The printed substrate can be further processed in the manufacturing process of the package, or the process of processing ends with printing.

An art image of a printed product can be made, configured, or simply saved as an electronic data file.

The artistic image may include data regarding the desired or specified colors for the respective elements of the product.

The dimensions and values disclosed in the description should not be understood as strictly limited to the listed exact numerical values. On the contrary, unless otherwise specified, each such size is intended both to indicate the value given in the description and to the functionally equivalent range of this value. For example, a size disclosed as “20 nm” means “approximately 20 NM ".

All documents cited in the detailed description of the invention, in the relevant part, are included here as reference information; reference to any document should not be construed as recognition that this document discloses the present invention. If any meaning or definition of a term in the description contradicts any meaning or definition of the same term in the document included as reference, then the meaning or definition of the term given in the description should be defining.

Although specific embodiments and / or individual features of the present invention have been described herein, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the appended claims are intended to cover all such changes and modifications that are within the scope of this invention.

Claims

CLAIM

1. A method of producing a sol-gel ink for color interference inkjet printing containing a nanocrystalline titanium dioxide sol in a solution of ethyl alcohol in water, in two stages, at the first stage, a nanocrystalline titanium dioxide sol of a predominantly anatase phase in water is obtained,

2. The method of obtaining sol-gel ink for color interference inkjet printing according to claim 1, characterized in that the nanocrystalline sol of titanium dioxide predominantly anatase phase in water is obtained by

the creation of an acidic medium and holding at 80 ° C for 1 hour with an increase in the content of the crystalline phase of the anatase phase titanium oxide and obtaining a nanocrystalline titanium dioxide sol of a predominantly anatase phase with titanium dioxide crystal size of not more than 200 nm, mainly 5-100 nm, with the average hydrodynamic diameter of the sol particles is not more than 30 nm, mainly 15.8 nm, with the zeta potential of the sol particles not less than +30 mV mainly +36 ± 5 mV,

stabilization of the nanocrystalline sol of titanium dioxide predominantly anatase phase by protonization of the sol particles in the presence of nitric acid and holding for 1-2 weeks at room temperature with constant stirring to obtain a stable nanocrystalline sol of titanium dioxide predominantly anatase phase with a content of the amorphous phase of titanium dioxide not more than 5% with a titanium dioxide crystal size of 5-200 nm predominantly anatase phase, with an average hydrodynamic diameter of sol particles of not more than 200 nm predominantly nificant 15.8 nm, a zeta potential of particles of a sol of at least +30 mV, preferably +36 ± 5 mV.

3. A method of producing a sol-gel ink for color interference inkjet printing according to claim 1, characterized in that the nanocrystalline sol of titanium dioxide in a solution of ethyl alcohol in water is obtained by

bringing the viscosity parameter of a nanocrystalline sol of a titanium dioxide of a predominantly anatase phase in water to an index of not more than 2.1 MPa * s by concentrating a sol of nanoparticles of titanium dioxide of a mainly anatase phase in water to a concentration of at least May 8. % by vacuum evaporation at a temperature of 50 ° C,

obtaining the required density and surface tension of the nanocrystalline sol of titanium dioxide predominantly anatase phase of not more than 25 mN / m by adding ethanol to a concentration of ethyl alcohol in water of not more than 70 mass. %.,

ensuring phase equilibrium between water and ethyl alcohol by homogenization for at least 12 days,

to obtain a nanocrystalline sol of titanium dioxide predominantly anatase in a solution of ethyl alcohol in water.

4. The method of obtaining sol-gel ink for color interference inkjet printing according to claim 3, characterized in that get nanocrystalline sol of titanium dioxide in a solution of ethyl alcohol in water, characterized by at least one of the following group of properties:

the presence of nanocrystalline particles of titanium dioxide in the form of crystals of titanium dioxide predominantly anatase phase with an amorphous phase of titanium dioxide content of not more than 5%,

the size of the nanocrystalline particles of titanium dioxide 5-200 nm, the average hydrodynamic diameter of the sol particles is not more than 200 nm, mainly 15 nm,

the zeta potential of sol particles is not less than +30 mV, mainly +36 ± 5 mV mV,

viscosity not more than 2.5 MPa * s, mainly 2, 1 MPa * s, surface tension not more than 30 nN / m, mainly 27 nN / m,

the duration of sedimentation stability of the sol is not less than 1 year.