WO2018038645A1 - Metameric multilayered pigment - Google Patents

Abstract

The present invention relates to multilayered pearlescent pigments which display a contrasting colour transition when the viewing angle or lighting conditions are altered, said multilayered pearlescent pigments being obtained using a transparent substrate, coloured with a metameric pigment or a metameric combination of pigments, by applying to said substrate at least one dielectric layer with an interference effect, which produces different colouration at different viewing angles, or at least two dielectric layers with an interference effect, which reflect at least two different areas of visible range at one viewing angle. The coloured transparent substrate is obtained using a surface-active colloidal solution of binder, containing ultrafine metameric pigments having a particle size of less than 80 nm. The resulting substrate makes it possible to reduce Fresnel light diffusion and enhance the contrast range in which the colour, refracted by the dielectric layers, alters when the viewing angle or the lighting conditions are altered.

Description

 METAMERIC MULTI-LAYERED PIGMENT

Technical field

 The present invention relates to a method for producing multilayer pearlescent pigments, in particular, to a technology for producing a colored transparent substrate having a thickness of 50 to 700 nm, and color-changing pigments based on it. The field of application of such pigments is decorative and automotive coatings, anticorrosion coatings, plastics, printing, especially printing inks for protective technologies, paints for glass and ceramics, decorative cosmetics.

State of the art

 A known method of producing flat particles of a substrate by expansion, drying and subsequent grinding of colloidal solutions of boron, aluminum and silicon compounds (US 3795524 A, 03/05/1974). In this way, particles of a substrate with a thickness of 1 to 25 μm are obtained. The disadvantage of this method is the impossibility of obtaining sufficiently thin particles of the substrate.

 Also known is a method for producing flat particles of a glass or ceramic substrate by grinding microspheres (US 4349456 A, 09/14/1982, US 3960583 A, 06/01/1976). A cheap way to obtain such microspheres is the foaming of hydrated granules of sodium silicate (US 5104632 A, 04/14/1992). It allows you to get colored particles of the substrate with a thickness of 0.1 to 100 microns. The disadvantages of this method include the too high angle of curvature of the resulting substrate.

 Also known is a method of producing flat particles of silicon dioxide by applying soluble glass to a movable tape, followed by drying, peeling and firing (EP 0240952 A2, 10/14/1987, US 5,294,237 A, 03/15/1994). This process requires bulky equipment, special methods for wetting a smooth substrate tape and maintaining the thickness of the film-forming coating. In addition, the process of film deposition on a polymer tape, drying and exfoliation causes equipment wear.

Also known is a method of producing thin glass particles by centrifugal spraying of a molten glass (US 8091385 B2, 01/10/2012). This method allows to obtain flat glass particles with a thickness of 700 to 900 nm. The preparation of a substrate based on glass melt is associated with high energy costs. Also known is a method of producing a colored substrate by blowing molten glass (US 2006/0048679 Al, 03/09/2006). This method allows to obtain substrate films with a thickness of 15 μm. This method, like the previous one, is associated with high energy costs and does not allow to obtain a sufficiently thin substrate.

 Patents US 5203974 A, 04/20/1993, US 6521671 B1, 02/18/2003, describe a method for producing thin colored films by precipitation of a surfactant from a solution and dispersion of hydrophobic conductive particles of about 10 microns or less in size by electrodeposition from a lyophobic colloidal solution. This method is not cheap enough for the industrial production of the substrate.

 US 3551244, 12.29.1970, also describes the preparation of thin films by curing hydrophobic polymer films on a water surface. This method allows to obtain films with a thickness of 50 nm to 5 μm. The disadvantage of this method is that it does not allow you to accurately adjust the thickness of the resulting film.

 There is also known a method of obtaining a substrate using vacuum deposition (EP

0370701 A, 05/30/1990). This method is the most expensive. In addition, all the described methods for producing a colored substrate do not allow to effectively increase the contrast of a multilayer color-varying pigment. Regular pearlescent pigment, reflecting any one color of the spectrum, becomes more contrast in combination with a dye of the same color. A color-changing pigment, reflecting two or more shades of the spectrum, inevitably loses the contrast of one of the reflection colors when the other is enhanced with conventional dyes or pigments.

 Patents are known which describe the use of multilayer pearlescent pigments in combination with metameric dyes (US 5059245, 10/22/1991). Since the well-known pearlescent pigments have two or more spectral shades only at different viewing angles, their use is limited to conventional color-changing paints. To enhance the metameric properties of dyes, nacre must reflect two or more shades at the same viewing angle.

A close analogue of this invention is the Merck patent (US 7255736 B2, 08/14/2007), which describes the preparation of a substrate with a thickness of 50 nm to 150 nm and a pigment based on it. Thin films are obtained by the known method of curing soluble glass deposited on a movable tape. Such thin films can eliminate the undesirable shade arising due to the Fresnel reflection of light on a substrate having a different shade depending on the thickness of the substrate. it It is especially important for multilayer pigment of white color and pigments with effect of silver color.

 Also known are methods of producing a substrate based on soluble glass and an interference pigment based on it, containing a translucent selectively absorbing metal layer (US 2011/0126735 A1, 06/02/2011, US 8900660 B2, 02/02/2014). Such a colored metal layer, unlike layers containing pigments, does not scatter light and has a more selective absorption than the layer of colored metal oxide. The described methods partially solve the problem of increasing the contrast of a color-variable pigment for some parts of the spectrum, but are not universal. The disadvantages of these known methods include the high cost of precursors for the deposition of metals from solution (metal acetylacetonates are usually used), as well as the limited selection of such coatings (from the point of view of economic feasibility, Ni, Cr and Zn are preferred). Selective absorption in the desired range is not always possible, and as a result, such a coating gives good results with a limited range of shades. In addition, thin (nanometer) dyed metal films, like conventional dyes, can weaken the color complementary to the transmittance.

The closest analogue of the present invention is the method described in patent US 6508876 B1, 01/21/2003. The method includes applying soluble glass with a concentration of 10-30% May containing dispersed organic or inorganic pigment particles or dissolved dyes or chromophore metal compounds onto a movable belt. In this manner, substrate particles having a thickness of 50 to 2000 nm are obtained. Obtaining a substrate by applying a thin silicate film on a moving tape has several disadvantages. Obtaining films with a thickness of less than 1 μm requires precision equipment and very precise control at all stages of production. At the same time, the surface of the polymer tape should have a very high degree of purity (low roughness). The smooth surface of the substrate, in turn, requires special means to improve the wetting of the surface and obtain a uniform coating. And removing the substrate with a squeegee, brush or ultrasound can lead to degradation of the surface of the moving tape. The use of a soluble separation layer to remove the substrate is associated with additional costs. The washing of the substrate is usually carried out by pulling the movable tape through a container with an acid solution, which also affects the wear of the equipment. This method is very effective for reducing the whiteness that occurs when Fresnel scattering of light at the interface between the pigments and the binder. It contributes to a more saturated color of pigments having a single color of reflection. But in the case of color-changing pigments, reflected colors that do not match the color of the substrate will weaken.

 In addition, staining the substrate with pigments known in the art gives a positive result only in the case of pearlescent pigments having a single reflection color. For example, the color of the red interference pigment can be enhanced by a substrate stained with red pigments (as described in US 2006/0156949 A1, 07.20.2016). But in the case of color-changing pigments, reflected colors that do not match the color of the substrate will weaken. If the colors reflected by the pigment are complementary, this can lead to the complete absorption of one of the reflected colors. If the second color is not completely opposite to the first, then this leads to subtractive mixing and dirty tones. Thus, the color of the multilayer color-changing pigment will have a bright color at one viewing angle and faded achromatic color at a different viewing angle.

Disclosure of invention

 The present invention is to overcome the disadvantages of the prior art and to develop a method for producing substrate particles with a thickness of less than 1 μm, containing metameric pigment or metameric combination of pigments, as well as multilayer color-changing pigment based on them.

 Another objective of the present invention is to obtain a multilayer metameric pigment that changes the color of reflection depending on the lighting conditions or when changing the viewing angle.

 The problem is solved in that:

 A film-forming colloidal solution is used to obtain a multilayer pigment substrate containing a dispersion of silica nanopowder in alkali metal alkylsiliconate as a binder, a metameric pigment or a metameric combination of pigments and a surfactant.

As a metameric pigment or metameric combination of pigments, the film-forming solution contains particles of selectively absorbing ultrafine pigment or combination of pigments with a diameter of less than 80 nm, having at least two transmittance maxima in the visible range. The film-forming solution may further contain an additive that promotes an increase in adhesion and a stabilizing additive.

 A method of obtaining a substrate of a multilayer pigment includes the following steps: feeding a film-forming solution to the foaming device to form a foam material; convective, radiation or inductive drying of the foam material; grinding dried foam to form substrate particles; washing the obtained particles with acid and water; drying and heat treatment of particles. As a foaming device, a frame blown by an air stream or a venturi can be used.

 The obtained substrate of a multilayer pigment based on a transparent film-forming substance is a particle containing a metameric pigment or a metameric combination of pigments.

 A method for producing a metameric multilayer pigment comprises applying to said substrate at least one dielectric layer with an interference effect, which gives different colors at different viewing angles or at least two dielectric layers with an interference effect that reflect at least two different parts of the visible range under one viewing angle.

 The obtained metameric multilayer pigment includes a transparent substrate containing a metameric pigment or metameric combination of pigments, coated with at least one dielectric layer with an interference effect, which gives a different color at different viewing angles or at least two dielectric layers with an interference effect that reflect at least at least two different sections of the visible range at the same viewing angle. The multilayer pigment may further comprise a metal reflective layer deposited directly on the substrate, and at least two dielectric layers with an interference effect that reflect at least two different parts of the visible range at one viewing angle.

 The technical result of this invention is a cheap and effective way to obtain a painted thin substrate and a bright color-changing pigment based on it.

The authors of the present invention have found that if a solvent forming a colloidal solution is used as a solvent for a film-forming substance, then films of such a film-forming, which arise upon evaporation of the solvent at the interface, form a coherent dispersed layer and have a very low vapor permeability for a given solvent. This explains the easy foaming of soluble glass and colloidal solutions of certain high molecular weight substances. A thin film of a soluble film-forming substance retains solvent vapor. Moreover, the mechanism of formation of such a foam differs from the mechanism of formation of foam of surfactants. Usually, to obtain a stable foam in the liquid phase, in addition to the solvent, at least one surface-active component must be present - a foaming agent adsorbed on the solution-air interface. Liquids that do not contain a surfactant do not form any stable foam, and substances that are in a molecularly dispersed state in the adsorption layer form a foam that quickly decomposes as the inter-membrane fluid expires. Nevertheless, many colloidal solutions that do not contain surfactants form a stable foam not due to the adsorption of surfactants on the interface, but due to the formation of insoluble films on the interface. At the same time, a film of a coherently dispersed layer formed on the surface prevents the loss of solvent vapor and easily foams when heated. Similarly, solutions of high molecular weight compounds in a solvent having a different polarity (for example, solutions of polyisocyanates or polyorganosilosanes in liquid freons) or lyophilized sols stabilized by electrolytes (for example, soluble silicate glass) behave in a similar manner. In such free-dispersed systems, the solvent does not form a true solution, and loss of solvent leads to a transition to a coherent dispersed state. The resulting films, like dried films of lyophobic sols, lose their solubility. The thickness of these films is usually greater than 1 μm. In addition, accurately adjusting the thickness of such films is a rather complicated task.

 Solid films thinner than 1 μm can be obtained by combining both mechanisms of foam formation. By adding surfactants to such a colloidal solution, it is possible to obtain a composition that forms “soap” bubbles that harden upon drying. Such bubbles can be obtained on the basis of solutions of organic or inorganic compounds, such as compounds of aluminum, silicon, potassium or sodium with borates, aluminum borates, aluminates, polyphosphates, metaphosphates, silicates, organosilicon compounds or a mixture of these substances. From a cost point of view, soluble glass is the preferred precursor.

Obtaining foam surfactants does not require sophisticated equipment. The substrate based on such a foam has a perfectly smooth surface. At of this, the film thickness of the surfactant solution is easy to adjust by changing parameters such as the density of the solution, the air flow rate, etc. Obtaining very thin films does not require additional costs. With a solids content of about 20%, a five-fold shrinkage of the silicate film occurs upon drying. Thus, even a relatively thick film of about 1 μm after drying will have a thickness of about 200 nm.

 The resulting substrate has the same optical properties as the substrate obtained using a more expensive method using a movable tape. Unlike mica and other natural materials, such a substrate does not have an admixture of extraneous polluting ions. It can also serve as a barrier to oxidation processes in anticorrosion coatings.

 The use of a pigment with metameric properties or a metameric combination of pigments for coloring a substrate eliminates the Fresnel reflection of light, which gives transparent pearlescent pigments an achromatic white hue, and, at the same time, enhances two or more colors reflected by a multilayer pigment. The use of a multilayer metameric dielectric coating allows one to enhance the metameric properties of conventional metameric pigments or to achieve a metameric effect in the spectral range where conventional pigments are not effective.

Multilayer pigments with the effect of interference usually reflect parts of the spectrum that correspond to one or another primary color, such as violet (390-455 nm), blue (455-492 nm), green (492-577 nm), yellow (577-597 nm) , orange (597-622 nm), red (622-770 nm). Organic pigments or d-metal compounds reflect mainly white light with a maximum absorption in the range corresponding to the complementary color. In this case, organic dyes, pigments based on dyes deposited on a substrate with a low refractive index (“varnishes”), compounds of polymers and dyes (polymer dyes) or pigments with a very low refractive index (“glaze” pigments) can have very low diffuse white light scattering. Organic pigments or d-metal compounds are known that absorb not the complementary color, but the spectral regions next to the complementary, which are called metameric. Such pigments give a color sensation similar to pigments having one absorption maximum when illuminated with white light, but when illuminated by other sources (such as a low pressure sodium lamp, halogen lamps, etc.) they can change color. Using such pigments or combinations of pigments to stain a multilayer substrate pigment, you can enhance the contrast of the color transition when changing the viewing angle of the color-variable pigment.

 Metameric properties that are independent of the viewing angle may also have a composition of dielectric layers with an interference effect. For example, a combination of shades of violet (380-430 nm), the interference color with orange (585-620 nm) gives a feeling of red, yellow (577-585 nm) with red (620-760 nm) gives a feeling of orange, yellow-green ( 560-577 nm) with red (620-760 nm) gives a yellow sensation, a combination of yellow (577-585 nm) with blue (470-495 nm) gives a green sensation, a combination of green (530-560 nm) with violet ( 380-430 nm) gives a blue sensation, a combination of blue-green (495-530 nm) with violet (380-430 nm) gives a blue sensation, a combination of violet (380-430 nm) with red (620-770 nm) yes m feeling purple (red-violet), and the combination of violet-red (760-770 nm) and blue (430-470 nm) gives a feeling violet. The combination of the substrate stained with metameric pigments and the metameric combination of dielectric layers makes it possible to obtain a metameric effect not achievable with the known metameric pigments.

 To obtain a metallic luster effect or for a darker, more saturated color reflected by the interference layer, the pigment composition may include not only transparent dielectric layers, but also a fully reflective metal layer (as described in US patent 6794037 B2, 09/21/2004) or a fully absorbing layer ( as described in patent US 8337609 B2, 02/02/2011 1).

The implementation of the invention

 The substrate may consist of silicon dioxide, silicates, boron oxide, borates, alumina, aluminum borate, tin oxide, cerium oxide and other transparent materials. The use of soluble glass material is preferred. Soluble glass should stretch easily. An essential factor in the preparation of thin films of soluble glass is its stickiness, which is manifested in the good wetting of various surfaces, high adhesion strength and low surface tension. High modulus solutions with a high content of colloidal particles are more sticky.

 Various additives also have a significant effect.

Thus, the addition of urea increases the adhesive ability of soluble glass without significantly affecting the viscosity. Such soluble glass in its properties becomes like molten glass. It can be drawn into long thin threads or films.

 Also, to stabilize the films, the solution may additionally contain various substances with the ability to form gel-like structures in the adsorption layers and interlayer volumes of the liquid, such as polyelectrolytes. Organic and inorganic polyelectrolytes such as ammonium pentaborate, sodium pentaborate, sodium hexametaphosphate, alginate, carrageenan, carboxymethyl cellulose, gum arabic, pectin, xanthan gum, ghatti gum, etc. can be used as such substances.

 Amides and amine oxides can also be used as foam stabilizers.

The addition of surfactants allows even thinner films to be obtained. In this case, the outflow of the solvent does not lead to the destruction of the films, as is the case with films of surfactants. Anionic surfactants such as primary sodium alkyl sulfates, sodium alkyl benzene sulfonates, sodium alkyl polyoxyethylene sulfate (sulfoethoxylate) may be used as a suitable surfactant; nonionic surfactants based on polyethylene oxide, etc. Commercially available soluble glass remains stable only with a low surfactant content and with not too strong dilution with water. Excess surfactants lead to an increase in the release of silica sol and an increase in turbidity during dilution. The process of separation of silica during the dilution with water of soluble glass based on alkali metal hydroxides leads to a significant deterioration in film-forming properties, an increase in porosity and brittleness of the resulting films. In addition, soluble glasses based on alkali metal hydroxides are very sensitive to additives of organic substances, and soluble glass based on quaternary ammonium bases has a very high cost. This disadvantage is eliminated by replacing such soluble glass with a transparent soluble glass based on a surface-active alkaline dispersant such as sodium methyl silicate or ethyl silicate, potassium methyl silicate or ethyl silicate or other commercially available alkali metal alkyl silicones, active functional groups = Si-ONa and = Si-OK which interact with surface active functional hydroxyl groups of silica nanopowder. Silica films based on such a solution have properties characteristic of ceramic varnish films, combining high transparency and hardness of quartz. The resulting solution of surface-active soluble glass can be colored using metameric pigments or metameric combination of pigments. Nanoparticles or ultrafine pigments with a diameter of less than 80 nm, preferably less than 30 nm, but not more than the thickness of the substrate to be coated, can be used as pigments. Such pigments can be obtained by condensation methods or by grinding commercially available pigments in a colloid mill. Fluorescent pigments, quantum dots, pigments for the IR and UV ranges can also be used as such nanoparticles. The pigment content in the substrate can vary from 0.5 to 40%, preferably from 5 to 15%.

 To obtain a stable pigment dispersion, various wetting agents can be used, such as ammonium and sodium salts of polyacrylic acids, nonionic dispersants, or high molecular weight block copolymers with pigment affinity groups (e.g. ANTITERRA 250 (manufactured by BYK-Chemie GmbH), Hydropallat 884 (manufactured by Henkel) and other

 As a metameric combination of pigments, compounds of d-metals and lanthanides with heteropoly acids, vanadic acids, silicic acid can be used; borates, phosphates, framates and molybdates, as well as light-resistant organic pigments such as fan-coat varnishes, carmine varnish, quinacridones, isoindolinones, diketo-pyrrole-pyrroles (DPP), dioxazine, phthalocyanine, disazo pigments, etc. some azopigments Particularly preferred for the preparation of metameric selective absorption are compounds of vanadium, iron, neodymium, praseodymium and cerium and strong varnishes of the main dyes based on heteropolyacids. Suitable pigments are described, for example, in patent US 6830822 B2, 12/14/2004.

 As pigments that improve the individual properties of a soluble glass substrate, such as haze or vice versa, reducing diffuse reflection, for example, bismuth phosphate, barium sulfate (BF 10, commercially available from Nordmann, Rassman GmbH & Co.), carbon black can be used. (EMPEROR 2000, EMPEROR 1800 manufactured by Cabot Corporation, Predisol® CAB PLA 0624 Black 7 manufactured by Sun Chemical), etc.

The composition may also contain ferromagnetic nanoparticles, such as iron, cobalt, nickel, iron oxide (III), barium ferrite, strontium ferrite, etc., which allows you to orient the pigment along the lines of the magnetic field to achieve Zd-φφeκτa. The dispersion of pigments in soluble glass is carried out using any equipment with high shear. For example, using a ball mill. To obtain bubbles of the same size with a uniform film thickness, special devices can be used (for example, a bubble generator described in US Pat. No. 6,062,935 A, 05.16.2000). The colored solution is fed to a frame through which an air stream is blown. The resulting foamed material in the form of individual bubbles enters the drying chamber with a temperature of about 30-60 ° C. At a higher temperature, the foam may collapse due to excessive expansion of the bubble; at a lower temperature, drying does not occur quickly enough. In addition, at a low drying temperature, a slight precipitate of the foam is possible as it dries. In other embodiments of the invention, heating may be by induction or infrared radiation. To prevent the bubbles from falling before they dry completely, the lower part of the drying chamber is filled with carbon dioxide. Thus, air-filled bubbles reach the end of the drying chamber without touching the base and walls of the chamber. Dried bubbles are crushed. Particles obtained on the basis of soluble glass are washed with acid and deionized water, and then finally dried at a temperature of 150-200 ° C and subjected to heat treatment at 400-600 ° C. When washing the obtained substrate for the selective removal of alkaline ions, it is advisable to use weak acids or acid salts (phosphoric acid, acetic acid, iron chloride solution, tin chloride solution, etc.). The concentration of acid can be from 1% to 20%. Residual acid is removed by washing in deionized water. Then, the resulting substrate is finally dried at a temperature of 150-200 ° C and subjected to heat treatment at 400-600 ° C.

 The particle diameter of the substrate after grinding and classification is preferably from 1 to 250 microns, more preferably from 5 to 100 microns. Their thickness is from 50 to 700 nm, preferably from 50 to 100 nm. The average aspect ratio (length and thickness) of the substrate is preferably from 10 to 200, more preferably from 20 to 150. With a lower aspect ratio, the multilayer pigments are difficult to align parallel to each other, which can lead to mixing colors reflected at an acute angle and an angle close to orthogonal and completely level the flip-flop effect.

To obtain pigments with a color-variable effect depending on the viewing angle, the composition of the pigment, except for a layer with a high refractive index, is usually contains an optically active dielectric layer with a low refractive index.

 As such a material, silicon dioxide is most preferred. The silica layer should preferably have an optical thickness in the range of 180-730 nm, more preferably 215-470 nm. The use of such a dielectric layer provides a variable optical path length for light of various spectral ranges depending on the angle of incidence of light, which leads to a color change depending on the viewing angle.

For a dielectric layer with a low refractive index, materials having a refractive index of about 1.65 or less are suitable, for example, silicon dioxide (Si0 ₂ ), alumina (A1 ₂ 0 ₃ ), magnesium fluoride (MgF ₂ ) _, aluminum fluoride (A1F ₃ ) _, cerium fluoride (CEF ₃ ), lanthanum fluoride (LaF ₃ ) _i sodium fluoroaluminate (e.g. Na ₃ AlF ₆ or Na ₅ Al ₃ Fi ₄ neodymium fluoride (NdF ₃ ) _; samarium fluoride (SmF ₃ ) _; barium fluoride (BaF ₂ ), calcium fluoride (CaF ₂ lithium fluoride (LiF), or combinations thereof.

 In order to obtain a strong interference effect, at least one high refractive index dielectric layer is applied to the low refractive index layer.

For a dielectric layer with a high refractive index, materials having a refractive index of 2 2, preferably 2,4 2.4; are suitable; they may be translucent (colored in transmitted light but not scattering light) or transparent, such as metal oxide, metal nitride or metal sulfide. Most preferred are tin dioxide (Sn0 ₂ ), titanium dioxide (TiO ₂ ), zirconia (Zr0 ₂ ), silicon carbide (SiC), zinc sulfide (ZnS), zinc oxide (ZnO), tantalum oxide (Ta ₂ 0 ₅ ) , cerium dioxide (Ce0 ₂ ), yttrium oxide (Y ₂ 0), europium oxide (Eu ₂ 0 ₃ ), hafnium nitride (HfN), hafnium carbide (HFC), hafnium oxide (НУ ₂ ), lanthanum oxide (bа ₂ 0з _); magnesium oxide (MgO), neodymium oxide (Nd ₂ 0 ₃ ), praseodymium oxide (Pr ₆ Oc), samarium oxide (Sm ₂ 0 ₃ ), indium oxide _, indium tin oxide (ITO), antimony trioxide (Sb ₂ 0 _3), silicon oxide (SiO), silicon nitride (Si ₃ N _4), selenium trioxide (Se ₂ 0 _3), tungsten trioxide (W0 _3), chromium oxide (Cr ₂ 0 _3), and combinations thereof. To reduce achromatic reflection, the interference layer should not be too thick (from about 5 to 150 nm).

To obtain pigments with a color-changing effect, depending on changes in lighting conditions, the pigment composition must contain at least two dielectric layers with interference effect, reflecting different parts of the visible range at the same viewing angle. Mixed shades of color obtained with additive mixing of light reflected by dielectric layers of similar color shades is very dependent on lighting conditions. In the absence of any of the shades involved in creating an additively mixed color shade in the spectrum of the light source, the color of the multilayer pigment changes. In this case, the colors reflected by the dielectric layers should be close enough to give a feeling of a different color, intermediate between them, with additive mixing. A composition comprising two or more dielectric layers having additional reflection colors or even having not sufficiently close reflection colors gives an achromatic white hue.

Examples

 Example 1. Obtaining a colloidal surfactant solution.

 To obtain a colloidal surfactant solution, a composition is prepared in the following ratio of components:

high-modulus soluble glass (soluble glass with a concentration of 770 g / l and silicate module M = Si ₂ / Me ₂ 0 = 3.68 based on sodium methylsiliconate and aerosil): 10-60%, preferably 40%;

 polyelectrolyte (ammonium pentaborate, sodium pentaborate, sodium hexametaphosphate, gum arabic or ghatti gum): 1 to 10%, preferably 5%;

 Surfactant (sodium sulfoethoxylate, etc.): 1-10%, preferably 2.5%;

 thickener (agar-agar or gelatin): 0.5%;

 adhesive additive (urea): 0.35 -2%, preferably 1.5%;

 pigment dispersion (50% solution in H20): 2-6%;

 deionized water: the rest.

Example 2. Obtaining a colorless substrate.

1.4 g of urea are dissolved in 40 g of high modulus soluble glass at a temperature of 60-90 ° C, preferably 70 ° C. Then, to a solution of the modified liquid glass, a solution of 5 g of sodium hexametaphosphate, 2.5 g of sodium sulfoethoxylate, 0.5 g of gelatin in 20 ml of deionized water is added. The resulting solution is fed to a frame through which an air stream is blown. Foamed material is dried to a solid state at a temperature of 40 ° C for 10 minutes, then incubated for 30 minutes at a temperature of 60 ° C, washed with 20% acetic acid solution and deionized water. Then dried for one hour at 150 ° C and annealed for 30 min at 500 ° C. The resulting colorless substrate is crushed and classified by particle size.

Example 3. Obtaining a colored substrate.

 1.4 g of urea are dissolved in 40 g of high modulus soluble glass at a temperature of 60-90 ° C, preferably 70 ° C. Then, a solution of modified liquid glass is added with a solution of 5 g of sodium hexametaphosphate, 2.5 g of sodium sulfoethoxylate, 0.5 g of gelatin, 30 g of a pigment dispersion (water dispersion of 0.5 g of stabilized prismatic silver silver nanoparticles (with a maximum absorption of about 527 nm) and 0.5 g of stabilized silver nanoparticles of a prismatic yellow form (with a maximum absorption of about 500 nm) and 0.5 g of stabilized silver nanoparticles of a prismatic blue form (with a maximum absorption of about 711 nm) in 20 ml of deion water, the resulting solution is fed to a frame through which a stream of air is blown in. The foam is dried to a solid state at a temperature of 40 ° C for 10 minutes, then incubated for 30 minutes at a temperature of 60 ° C, washed with a 20% solution of acetic acid and deionized water Then it is dried for one hour at 150 ° C and annealed for 30 minutes at 500 ° C. The substrate is crushed and classified according to particle size.The resulting substrate transmits light in yellow, blue and purple hues.

Example 4. Obtaining a colored substrate.

In 40 g of high-modulus soluble glass at a temperature of 60-90 ° C, preferably 70 ° C, 1, 4 g of urea is dissolved. Then, a solution of 5 g of sodium hexametaphosphate, 2.5 g of sodium sulfoethoxylate, 0.5 g of gelatin, 30 g of pigment dispersion (water dispersion of 1.5 g of stabilized silver prismatic silver nanoparticles (with a maximum absorption of about 572 nm)) in 20 ml of deionized water. The resulting solution is fed to a frame through which a stream of air is blown. Foamed material is dried to a solid state at a temperature of 40 ° C for 10 minutes, then incubated for 30 minutes at a temperature of 60 ° C, washed with 20% acetic acid solution and deionized water. Then it is dried for one hour at 150 ° C and annealed for 30 minutes at 500 ° C. The substrate is crushed and classified by particle size. The resulting substrate transmits light in violet, green and red hues. Example 5. Obtaining a multilayer pigment with a contrasting color transition when changing the viewing angle

50 g of a substrate with a particle size of from 20 to 50 μm obtained in example 3, dispersed in 750 ml of deionized water and heated to 75 ° C. To this dispersion, a 40% aqueous solution of TiCl _{4 is} poured through a dropping funnel until a violet colored 250 nm thick titanium dioxide film is deposited. In this case, the pH is maintained at 2.2 by the addition of a 30% NaOH solution. The resulting pigment is filtered and washed with deionized water. A layer with a low refractive index is then applied. The titanium dioxide coated pigment is dispersed in 150 ml of a 25% aqueous solution of ethanol and 15 ml of a 25% solution of ammonia. A solution of 250 ml of tetraethoxysilane in 125 ml of ethanol is poured into this dispersion at a rate of 160 ml / h until a green silicon film of thickness 350 nm is deposited. The pigment is filtered and washed with deionized water. The pigment coated with a layer of silicon dioxide is dispersed in 750 ml of deionized water and heated to 75 ° C. A 40% aqueous solution of TiCl _{4 is} poured onto this dispersion at a rate of 2 ml / min until a green titanium dioxide film 320 nm thick is deposited. In this case, the pH is maintained at 2.2 by the addition of a 30% NaOH solution. The resulting pigment is filtered and washed with deionized water. The pigment washed to a neutral pH is dried for 30 minutes at 150 ° C and then annealed at 800 ° C for 30 minutes. The resulting pigment has a bright green color of interference at a right viewing angle and purple at an acute viewing angle.

 Example 6. Obtaining a multilayer pigment with a contrasting color transition when changing lighting conditions.

 The first layer with blue interference color:

50 g of a substrate with a particle size of 5 to 20 μm obtained in example 2, is dispersed in 750 ml of deionized water and heated to 75 ° C. A 40% aqueous solution of TiCl ₄ is added to this dispersion at a rate of 2 ml / min until a blue titanium dioxide layer 300 nm thick is deposited. In this case, the pH is maintained at 2.2 by the addition of a 30% NaOH solution. The pigment is filtered and washed with deionized water. The resulting pigment has a blue interference color.

 Second layer:

A thin intermediate layer of silicon dioxide is applied to the first layer. The pigment coated with the first layer of titanium dioxide is dispersed on a stirrer in 750 ml of isopropanol and 240 ml of deionized water are added. Then the pH was adjusted to 10 by the addition of ammonium hydroxide. Heated to 75 ° C and poured through a drip funnel of 50 g of tetraethoxysilane. Then it is kept on a mixer for 2 hours, filtered, washed with isopropanol and dried at 150 ° C for 30 minutes.

 Third layer with yellow interference color:

50 g of pigment coated with a blue titanium dioxide layer of interference and an intermediate layer of silicon dioxide are dispersed in 750 ml of deionized water and heated to 75 ° C. A 40% aqueous solution of TiCl ₄ is added to this dispersion at a rate of 2 ml / min until a yellow titanium dioxide layer is deposited with a thickness of 100 nm. In this case, the pH is maintained at 2.2 by the addition of a 30% NaOH solution. The pigment is filtered and washed with deionized water. Then dried at 150 ° C and annealed at 800 ° C for 30 minutes. The resulting pigment has a metameric green color of interference, consisting of spectral blue and spectral yellow.

Example 7. Obtaining a pigment with a metal reflective layer.

 First layer:

 50 g of a substrate with a particle diameter of 5 to 50 μm are dispersed on a magnetic stirrer in 200 ml of a 2% dextrose solution. Then, a solution obtained by mixing 4 g of silver nitrate in 200 ml of distilled water and a 29% solution of ammonium hydroxide, poured through a dropping funnel to a brown precipitate, which is dissolved at an excess concentration of ammonium hydroxide, is added to the dispersion. The dispersion is kept on a mixer for 20 minutes, filtered and washed with deionized water.

 Second layer:

 An intermediate layer of silicon dioxide is applied to the first layer. The pigment coated with a metal layer is dispersed in 150 ml of a 25% aqueous solution of ethanol and 15 ml of a 25% solution of ammonia. A solution of 250 ml of tetraethoxysilane in 125 ml of ethanol is poured into this dispersion at a rate of 160 ml / h. The pigment is filtered and washed with deionized water.

 Third layer:

The substrate containing the metal reflective layer is dispersed in 750 ml of a solution of deionized water and ammonia with a pH of about 11 on a magnetic stirrer. A 1% solution of peroxotitanic acid obtained by dissolving titanium dioxide (anatase), titanium nitride or orthotitanic acid in hydrogen peroxide is added to the resulting dispersion at a rate of 1 ml / min. After the deposition of a layer of titanium dioxide with a thickness of 240 nm, red, the obtained pigment is filtered and washed with deionized water. Fourth layer:

 An intermediate layer of silica is again applied to the third layer. The pigment is dispersed in 150 ml of a 25% aqueous solution of ethanol and 15 ml of a 25% solution of ammonia. A solution of 250 ml of tetraethoxysilane in 125 ml of ethanol is poured into this dispersion at a rate of 160 ml / h. The pigment is filtered and washed with deionized water.

 Fifth layer:

 The pigment is dispersed in 750 ml of a solution of deionized water and ammonia with a pH of about 11 on a magnetic stirrer. A 1% solution of peroxotitanic acid obtained by dissolving titanium dioxide (anatase), titanium nitride, or orthotitanic acid in hydrogen peroxide is poured to the resulting dispersion at a rate of 1 ml / min. After deposition of a 320 nm thick titanium dioxide layer of green color, the pigment is filtered and washed with deionized water. Then dried at 120 ° C for 2 hours and annealed at 800 ° C. The resulting pigment has a metameric light blue reflection color that does not contain spectral blue color and a strong metallic luster.

Claims

CLAIM 1. A film-forming colloidal solution for producing a multilayer pigment substrate, containing a dispersion of silica nanopowder in an alkali metal alkylsiliconate solution as a binder, a metameric pigment or a metameric combination of pigments and a surfactant. 2. The film-forming colloidal solution according to claim 1, containing, as a metameric pigment or metameric combination of pigments, particles of selectively absorbing ultrafine pigment or combination of pigments with a diameter of less than 80 nm, having at least two transmittance maxima in the visible range. 3. Film-forming colloidal solution according to p. 1 or p. 2, additionally containing an additive that helps to increase adhesion. 4. A film-forming colloidal solution according to claim 1 or claim 2, further comprising a stabilizing additive. 5. A method of obtaining a substrate of a multilayer pigment, comprising the following stages:  the filing of the foaming device film-forming solution according to any one of paragraphs. 1-4 with the formation of foam;  convective, radiation or inductive drying of the foam material; grinding dried foam to form substrate particles;  washing the obtained particles with acid and water;  drying and heat treatment of particles. 6. The method according to p. 5, in which as a foaming device using a frame blown by a stream of air. 7. The method of claim 5, wherein a venturi is used as the foaming device. 8. A substrate of a multilayer pigment based on a transparent film-forming substance in the form of particles containing a metameric pigment or a metameric combination of pigments. 9. A method of producing a metameric multilayer pigment, comprising applying to the substrate according to claim 8 at least one dielectric layer with an interference effect, which gives different colors at different viewing angles or at least two dielectric layers with an interference effect that reflect at least two different sections of the visible range at the same viewing angle. 10. A metameric multilayer pigment comprising a transparent substrate containing a metameric pigment or a metameric combination of pigments, coated with at least one dielectric layer with an interference effect that gives a different color at different viewing angles or at least two dielectric layers with an interference effect that reflect at least two different parts of the visible range at one viewing angle. 11. The metameric multilayer pigment according to claim 10, which further comprises a metal reflective layer deposited directly on the substrate, and at least two dielectric layers with an interference effect that reflect at least two different parts of the visible range at one viewing angle.