Retroreflective compositions for industrial 3D spray painting of large surfaces

Abstract

The invention provides a retroreflective ink, coating or paint composition consisting of, based on the total weight of the composition: • 15-75 wt% solvent; • 1-85 wt% spherical glass beads having a median particle size D50 measured using laser diffraction of between 1 and 150 µm and a refractive index of between 1.5 and 2.8 measured at a wavelength λ of 589 nm, wherein optionally at least part of the hemispheres of the spherical glass beads are coated with a light-reflective coating; • 0.05-2.5 wt% one or more thickening agents; and • 0.20-4.5 wt% synthetic pigment platelets having an average diameter of between 1 and 75 µm, a thickness of less than 1 µm, and an aspect ratio (platelet diameter / thickness) of at least 10; • 0-2 wt% one or more pigment platelets or particles (D) other than synthetic pigment platelets (A), (B) and (C); • 0-30 wt% one or more additional ingredients, wherein the combined amount of the synthetic pigment platelets (A), (B) and (C) and the one or more pigment platelets or particles (D) is between 0.20 and 4.5 wt%.

Description

Technical Field

[0001] This invention relates to retroreflective inks, coatings, or paint compositions and methods for their preparation. The invention further relates to a method for coating a substrate having a retroreflective layer using the retroreflective ink, coating, or paint, and to a substrate having a retroreflective layer obtainable by this method. Background Technology

[0002] Retroreflective paints, inks, and coatings are used in a variety of applications. For example, they improve the visibility of road signs, road numbering markings, textiles, and automobiles in dark conditions. Paints, inks, and coatings typically provide retroreflective properties by adding spherical glass beads with a specific refractive index. Retroreflection occurs through a series of refractions: incident light is refracted through the upper surface of the spherical glass bead, internally refracted from the lower surface, and then further refracted as the light leaves the upper surface and travels back in the direction from which the incident light originated.

[0003] WO2004 / 017104A2 discloses a retro-projection composition comprising retro-projection microspheres, an adhesive system, and a thixotropic blend comprising at least two thixotropic anti-tack agents in amounts from about 2% to about 5% by weight based on the retro-projection composition. The retro-projection composition is intended for use as paints, inks, and coatings and is applied to a substrate using an aerosol applicator with a propellant.

[0004] WO01 / 16223A1 relates to reflective inks for printing on textiles. A single example of WO01 / 16223A1 discloses screen printing inks. Screen printing inks are not suitable for professional or industrial (high-speed) spraying. It is generally known to those skilled in the printing industry that screen printing inks and inks used for professional or industrial (high-speed) spraying have fundamentally different rheological properties because the techniques used to apply them to the substrate are fundamentally different.

[0005] WO00 / 42113A1 relates to reflective inks containing microbeads in a liquid carrier medium. The inks are intended for use in web printing on textiles.

[0006] WO2003 / 016964A2 relates to a retro-coating system and a method for providing the coating system on a substrate. The method includes the following steps:

[0007] (a) Applying a coloring composition to a substrate to form an uncured film layer of the coloring composition; and

[0008] (b) Applying a transparent coating composition that is at least partially transparent to an uncured film layer of a color-providing composition using a wet-in-wet technique, thereby forming an uncured film layer of the transparent coating composition on the uncured film layer of the color-providing composition;

[0009] At least one of the coloring composition and the transparent coating composition is crosslinkable, and at least one of the coloring composition and the transparent coating composition includes retroreflective microspheres on a substrate to provide a retroreflective coating system. The coloring base coating composition contains 5 to 40 parts by weight of pigment, such as flake aluminum pigment, such as 8 to 25 parts by weight, based on 100 parts by weight of the coloring base coating composition.

[0010] As is generally understood by those skilled in the art, when coating or painting a substrate, the intended effect of the paint or varnish is to provide coverage across the entire surface, regardless of whether the substrate or its surface is uneven. Clearly, if a reflective property is to be provided to the substrate, uniform reflectivity across the entire surface will be achieved. Similarly, if a colored paint or varnish layer is to be provided to the substrate, color differences present on the substrate to be coated or painted must no longer be visible through the colored paint or varnish layer; that is, the colored paint or varnish layer should be sufficiently opaque. Hereinafter, the term "sufficiently opaque" will be replaced with "having sufficient coverage" or "having sufficient concealing ability." In the context of this invention, these three terms refer to inks, paints, or coating formulations that, when applied to a substrate, mask any color differences present on the surface of the substrate. As is generally known to those skilled in the art, color unevenness is common on large substrates such as automotive bodies that require painting or coating.

[0011] The inventors have discovered that the retroreflective and coverage properties of prior art coatings or paints containing pigments and retroreflective spherical glass beads conflict in that the amount of pigment typically required to achieve sufficient coverage is greatly reduced or even completely destroyed in terms of retroreflective properties.

[0012] Figure 4 of WO2003 / 016964A2 discloses a coating system with aluminum pigment, wherein retroreflective microspheres are disposed in a colored base coating film. As explained above, WO2003 / 016964A2 teaches that the colored base coating composition contains 5 to 40 parts by weight of pigment, such as flake aluminum pigment, such as 8 to 25 parts by weight, based on 100 parts by weight of the colored base coating composition. As shown in the accompanying examples, the inventors have found that using at least 5 parts by weight of pigment in a base coating composition in which retroreflective microspheres are disposed has a detrimental effect on the retroreflective properties of the base coating film.

[0013] This problem can be solved by first applying an underlayer containing an amount of pigment that provides sufficient coverage, followed by applying a second layer containing retroreflective spherical glass beads on top of the underlayer. (WO2003 / 016964A2) Figure 1The examples in paragraphs

[00043] -

[00046] disclose, for example, a retroreflective coating system comprising retroreflective microspheres disposed in an intermediate coating layer between a colored base coating layer and a clear coating layer. However, this solution requires a manufacturing method that is undesirable in that it includes subsequent painting or coating steps with different compositions.

[0014] Reflective inks, coatings, or paint compositions are required that are stable during storage and can still be preferably applied to a variety of substrates using professional or industrial (high-speed) spraying to produce a reflective layer or coating with good coverage.

[0015] Therefore, the objective of this invention is to provide reflective ink, coating, or paint compositions that have sufficient stability or shelf life and can preferably be applied professionally or industrially to a variety of substrates using professional or industrial (high-speed) spraying.

[0016] Another objective of the present invention is to provide retroreflective inks, coatings, or paints that can be preferably applied to a variety of substrates using professional or industrial (high-speed) spraying to produce a retroreflective layer or coating with good coverage.

[0017] Another objective of the present invention is to provide a simplified method for producing a retroreflective layer with high coverage on large surfaces, such as automobile bodies, preferably using professional or industrial (high-speed) spraying. Summary of the Invention

[0018] The inventors unexpectedly determined that one or more objectives can be achieved by using an ink, coating, or paint composition comprising retroreflective spherical glass beads and a reduced amount of pigment in the form of flakes with specific dimensions.

[0019] Therefore, in a first aspect, the present invention provides a reflective ink, coating, or paint composition, which, based on the total weight of the composition, comprises the following:

[0020] • 15% to 75% by weight of solvent;

[0021] • 1% to 85% by weight of spherical glass beads, the median particle size D50 of which is between 1 μm and 150 μm as measured by laser diffraction, and the refractive index between 1.5 and 2.8 as measured at a wavelength λ of 589 nm.

[0022] • 0.05% to 2.5% by weight of one or more thickeners; and

[0023] • 0.20% to 4.5% by weight of synthetic pigment flakes, wherein the synthetic pigment flakes have an average diameter between 1 μm and 75 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10, wherein the synthetic pigment flakes are selected from (A), (B), (C) or a combination thereof;

[0024] (A) A metal sheet or synthetic mica sheet, optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, MgF2, metal alloys, and rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders.

[0025] (B) A sheet comprising Al2O3, SiO2, glass, ceramic, graphite and mica flakes, the sheet being coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders;

[0026] (C) A sheet comprising Al2O3 flakes doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxide, the sheet being coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders;

[0027] • 0% to 2% by weight of one or more pigment flakes or particles (D) other than synthetic pigment flakes (A), (B) and (C);

[0028] • 0% to 30% by weight of one or more additional ingredients,

[0029] The combined amount of synthetic pigment flakes (A), (B) and (C) and one or more pigment flakes or particles (D) is between 0.20% by weight and 4.5% by weight, preferably between 0.20% by weight and 4.0% by weight.

[0030] The inventors have discovered that this composition can be applied to various substrates, for example, using professional or industrial (high-speed) spraying, to produce a retroreflective coating layer with excellent coverage. Not wishing to be bound by any theory, the inventors hypothesize that a ratio of the average (surface) diameter of the synthetic pigment flakes between 1 and 75 μm, such as between 5 and 50 μm, and their smooth surface area provides sufficient coverage without unduly reducing reflectivity. Improved coverage generally indicates lower retroreflectivity. However, it is believed that the reflectivity of the smooth surface area of ​​the synthetic pigment flakes again improves retroreflectivity. Not wishing to be bound by any theory, the inventors further hypothesize that the very limited thickness of the synthetic pigment flakes (approximately the wavelength of visible light) further contributes to the retroreflective properties.

[0031] The inventors further determined that retroreflective ink, coating, or paint compositions can be applied to various substrates to produce a retroreflective coating layer with excellent color perception, similar to the color perception of ink, coating, or paint compositions that do not have retroreflective properties.

[0032] In a second aspect, the present invention relates to a method for coating a substrate with a retroreflective layer, the method comprising the following steps:

[0033] a) Provide a substrate;

[0034] b) Optionally, apply a primer layer to the substrate of step (a);

[0035] c) Optionally, but not preferably, a coloring underlayer is applied to the substrate of step (a) or the primer layer of step (b);

[0036] d) Spraying a reflective ink, coating, or paint composition as defined above onto the substrate of step (a) or the layer of step (b) or (c) in an amount provided of 0.25 and 30 g / m 2 The combined amounts of synthetic pigment flakes (A), (B), and (C) and one or more pigment flakes or particles (D);

[0037] e) Dry and cure the substrate coated with the retroreflection layer obtained in step (d); and

[0038] f) Optionally, coat the dried substrate coated with the retroreflective layer obtained in step (e) with one or more additional transparent coating layers, and then dry or cure it.

[0039] In a third aspect, the present invention relates to a substrate coated with a retroreflective layer, which can be obtained by a method for coating a substrate as defined herein.

[0040] definition

[0041] In the context of the retro-ink, coating, or paint compositions of the present invention, the term "shear dilution behavior" refers to the reduction in viscosity when a retro-ink, coating, or paint composition initially in a static state is subjected to a shear rate.

[0042] As used herein, the term "pigment" refers to particulate colorants, such as spherical portions or flakes. They are insoluble in the adhesives or solvents used.

[0043] As used herein, the term "dye" refers to a colorant that is molecularly soluble in the adhesive or solvent used.

[0044] As used in this article, the term "colorant" refers to pigments and dyes.

[0045] As used herein, the term "low-valence titanium oxide" refers to a titanium oxide having the formula Ti n O 2n-1 Titanium oxide compounds, where n is an integer greater than 1. Attached Figure Description

[0046] Figure 1 The coverage of the reflective ink, coating, or paint composition under normal lighting conditions is shown. Figure 2 The coverage and reflectivity of the ink, coating, or paint composition under the application of torch light (“flash”) are shown. Detailed Implementation

[0047] In a first aspect, the present invention relates to a reflective ink, coating, or paint composition, wherein, based on the total weight of the composition, the composition comprises the following:

[0048] • 15% to 75% by weight of solvent;

[0049] • 1% to 85% by weight of spherical glass beads, the median particle size D50 of which is between 1 μm and 150 μm as measured by laser diffraction, and the refractive index between 1.5 and 2.8 as measured at a wavelength λ of 589 nm.

[0050] • 0.05% to 2.5% by weight of one or more thickeners; and

[0051] • 0.20% to 4.5% by weight of synthetic pigment flakes, wherein the synthetic pigment flakes have an average diameter between 1 μm and 75 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10, wherein the synthetic pigment flakes are selected from (A), (B), (C) or combinations thereof;

[0052] (A) A metal sheet or synthetic mica sheet, optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, MgF2, metal alloys, and rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders.

[0053] (B) A sheet comprising Al2O3, SiO2, glass, ceramic, graphite and mica flakes, the sheet being coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders;

[0054] (C) A sheet comprising Al2O3 flakes doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxide, the sheet being coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders;

[0055] • 0% to 2% by weight of one or more pigment flakes or particles (D) other than synthetic pigment flakes (A), (B) and (C);

[0056] • 0-30% by weight of one or more other ingredients,

[0057] The combined amount of synthetic pigment flakes (A), (B) and (C) and one or more pigment flakes or particles (D) is between 0.20% by weight and 4.5% by weight, preferably between 0.20% by weight and 4.0% by weight.

[0058] In a highly preferred embodiment, the first aspect relates to a reflective ink, coating, or paint composition, which, based on its total weight, comprises the following:

[0059] • 15-68% by weight of solvent;

[0060] • 10-50% by weight of spherical glass beads, the median particle size D50 of which is between 5 and 150 μm as measured by laser diffraction, and the refractive index between 1.5 and 2.8 as measured at a wavelength λ of 589 nm.

[0061] • 0.05-2.5% by weight of one or more thickeners; and

[0062] • 0.20% to 4.5% by weight of synthetic pigment flakes, wherein the synthetic pigment flakes have an average diameter between 5 μm and 50 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10, wherein the synthetic pigment flakes are selected from (A), (B), (C) or combinations thereof.

[0063] (A) A metal sheet or synthetic mica sheet, optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, MgF2, metal alloys, and rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders.

[0064] (B) A sheet comprising Al2O3, SiO2, glass, ceramic, graphite and mica flakes, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders.

[0065] (C) A sheet comprising Al2O3 flakes doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxide, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders;

[0066] • 0% to 2% by weight of one or more pigment flakes or particles (D) other than synthetic pigment flakes (A), (B) and (C);

[0067] • 0-30% by weight of one or more other ingredients,

[0068] The combined amount of synthetic pigment flakes (A), (B) and (C) and one or more pigment flakes or particles (D) is between 0.20% by weight and 4.5% by weight, preferably between 0.20% by weight and 4.0% by weight.

[0069] In a preferred embodiment, the reflective ink, coating, or paint remains stable for at least 1 day, more preferably at least 2 days, at least 5 days, at least 10 days, at least 1 month, at least 2 months, at least 6 months, at least 1 year, or at least 2 years, wherein the composition is considered stable if no precipitation, condensation, or separation can be observed during visual and tactile inspection. In a preferred embodiment, the reflective ink, coating, or paint composition remains spray-stable for at least 24 hours. The composition is considered spray-stable if it is sprayed without premixing.

[0070] solvent

[0071] In the embodiments, the solvent is an aqueous solvent or water. As used herein, the term "aqueous solvent" means a solvent comprising at least 70% by weight of an aqueous solvent, preferably at least 80% by weight of water, more preferably at least 90% by weight of water, and even more preferably at least 95% by weight of water, such as at least 96%, at least 97%, and at least 98% by weight. Other solvents in the aqueous solvent are not particularly limited, but are generally water-miscible organic solvents, such as alcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol), polyols (e.g., ethanol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, hexanediol, pentanediol, glycerol, glycerol, or thiodiglycol), and glycol derivatives such as ethers or esters (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diethyl ether). Esters, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether or ethylene glycol monophenyl ether), amines (e.g., ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine or tetramethylpropylenediamine), amides (e.g., formamide, N,N-dimethylformamide or N,N-dimethylacetamide), dimethyl sulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidinone, 1,3-dimethyl-2-imidazolium dione, acetonitrile, acetone and combinations thereof.

[0072] In another embodiment, the solvent is an organic solvent or a mixture of organic solvents. Preferably, the organic solvent is selected from the group consisting of: aliphatic and aromatic solvents, ketones, esters, glycol ethers, alcohols, halogenated hydrocarbons, and combinations thereof. The most preferred organic solvents are selected from the group consisting of: xylene (a mixture of isomers), toluene, ethylbenzene, naphtha, 1,2,4-trimethylbenzene, trimethylbenzene, n-propylbenzene, isoamyl acetate, n-butyl acetate, (2-methoxymethylethoxy)propanol, 2-butoxyethyl acetate, 2-methylbutyl acetate, isobutanol, 1-butanol, 1-ethoxypropane-2-ol, 2,6-dimethyl-4-heptanone, 2-methoxy-1-methylethyl acetate, 4,6-dimethyl-heptane-2-one, 4-methyl-2-pentanone, 1-methoxy-2-propanol, 1-methoxy-2-propyl acetate, 2-(2-butoxyethoxy)ethanol, 2-butoxyethanol, 5-methylhexane-2-one, ethyl acetate, and combinations thereof.

[0073] In a very preferred embodiment, the amount of solvent is from 15% to 68% by weight, based on the total weight of the composition.

[0074] In the embodiments, the amount of solvent is 20% to 68% by weight, 30% to 68% by weight, 40% to 68% by weight, 50% to 68% by weight, or 52% to 68% by weight, based on the total weight of the composition.

[0075] In other embodiments, the amount of one or more additional components is 25% to 67% by weight, 35% to 66% by weight, or 45% to 65% by weight, based on the total weight of the composition.

[0076] In the embodiments, the amount of solvent is 20% to 75% by weight, 30% to 75% by weight, 40% to 75% by weight, 50% to 75% by weight, or 52% to 75% by weight, based on the total weight of the composition.

[0077] Spherical glass beads

[0078] As defined above, the refractive index of spherical glass beads measured at a wavelength λ of 589 nm is between 1.5 and 2.8.

[0079] In a preferred embodiment, the refractive index of the spherical glass bead measured at a wavelength λ of 589 nm is:

[0080] (a) Between 2.0 and 2.8, preferably between 2.1 and 2.4; or

[0081] (b) Between 1.7 and 2.1, preferably between 1.8 and 2.0.

[0082] In a preferred embodiment, as used herein, the term "glass" in "spherical glass beads" refers to a non-crystalline, amorphous solid and transparent material made of oxides. In other embodiments, the term "glass" in "spherical glass beads" refers to a solid and transparent material made of oxides and containing some microcrystalline properties. The refractive index of spherical glass beads is closely related to the density of the glass, although the relationship is not linear. Due to the properties of glass, density is approximately an additive function of its composition. Spherical glass beads with a refractive index between 1.5 and 2.8 typically have densities between 2.5 and 4.5 g / cm³. 3 The changes between them.

[0083] Oxides that can be used in glass include oxides of silicon, boron, aluminum, sodium, barium, vanadium, titanium, lanthanum, strontium, zirconium, potassium, magnesium, iron, calcium, zinc, lithium, barium, and lead. Spherical glass beads can contain, for example, different combinations of the following: silicon dioxide (SiO2), boron oxide (B2O3), phosphorus pentoxide (P2O5), vanadium pentoxide (V2O5), arsenic trioxide (As2O3), germanium oxide (GeO2), calcium oxide (CaO), sodium oxide (Na2O), magnesium oxide (MgO), zinc oxide (ZnO), aluminum oxide (Al2O3), potassium oxide (K2O), ferric oxide (Fe2O3), lead oxide (PbO), barium oxide (BaO), barium titanate (BaTiO3), titanium dioxide (TiO2), lithium oxide (Li2O), strontium oxide (SrO), lanthanum oxide (La2O3), and zirconium dioxide (ZrO2). Silicon dioxide and boron oxide typically have the lowest densities. Glasses containing a large percentage of these oxides typically produce glass beads with a low refractive index. The refractive index is increased by adding oxides with higher molecular weights.

[0084] Preferably, the spherical glass beads do not contain PbO.

[0085] Glass beads with a refractive index ranging from 1.5 to 2.51 and composed of oxides are disclosed in WO2014 / 109564A1, which is incorporated herein by reference in its entirety. Transparent glass beads without PbO and with a refractive index greater than 2.15 are disclosed in US4,082,427, which is incorporated herein by reference in its entirety.

[0086] Spherical glass beads can be colored spherical glass beads, as long as they remain transparent. This invention covers colored spherical glass beads made of colored transparent glass and spherical glass beads provided with a concentric transparent colored coating. The color can be a natural color caused by a composition of oxides or can be intentionally selected by adding a colorimetric component. Colored glass beads with high refractive index and high transparency are disclosed in WO2014 / 109564A1.

[0087] Therefore, in the embodiments, at least a portion of the spherical glass beads are glass beads made of colored transparent glass and / or at least a portion of the spherical glass beads are provided with a concentric transparent colored coating.

[0088] Spherical glass beads have a median particle size D50, as measured using laser diffraction. Therefore, based on volume distribution, the median particle size D50 is the median value in volume. The median particle size D50 is less than half the diameter of the population of spherical glass beads. This median particle size in volume is commonly referred to in this technique as Dv50 or D... v0.5 .

[0089] In a highly preferred embodiment, the median particle size D50 of the spherical glass beads, as measured using laser diffraction, is between 5 and 150 μm.

[0090] In an embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 25 and 100 μm, preferably between 30 and 75 μm, and more preferably between 35 and 50 μm.

[0091] In a preferred embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 5 and 100 μm, such as between 5 and 75 μm, between 5 and 50 μm, between 5 and 45 μm, between 5 and 40 μm, or between 5 and 35 μm.

[0092] In a highly preferred embodiment, the median particle size D50 of the spherical glass beads, as measured using laser diffraction, is between 1 and 100 μm, such as between 1 and 75 μm, between 1 and 50 μm, between 1 and 45 μm, between 1 and 40 μm, between 1 and 35 μm, between 1 and 30 μm, between 1 and 25 μm, between 1 and 20 μm, between 1 and 15 μm, or between 1 and 10 μm.

[0093] In yet another embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 25 and 150 μm, such as between 50 and 150 μm, 75 and 150 μm, 100 and 150 μm, 110 and 150 μm, or 115 and 150 μm.

[0094] Diameters D10 and D90 are typically referred to as Dv10 or D in this technology, respectively. v0.1 and Dv90 or D v0.9 The diameter of D10 is less than 10% of the diameter of the spherical glass bead group. Similarly, the diameter of D90 is less than 90% of the diameter of the spherical glass bead group.

[0095] The particle size distribution of spherical glass beads, as measured by laser diffraction, is defined by the following:

[0096]

[0097] In another embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 15 and 100 μm, and the span is between 0 and 1.9, preferably between 0 and 1.5, more preferably between 0 and 1, even more preferably between 0 and 0.5, such as between 0 and 0.2 or between 0 and 0.1.

[0098] In a preferred embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 30 and 75 μm, and the span is between 0 and 1.9, preferably between 0 and 1.5, more preferably between 0 and 1, even more preferably between 0 and 0.5, such as between 0 and 0.2 or between 0 and 0.1.

[0099] In another preferred embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 15 and 50 μm, and the span is between 0 and 1.9, preferably between 0 and 1.5, more preferably between 0 and 1, even more preferably between 0 and 0.5, such as between 0 and 0.2 or between 0 and 0.1.

[0100] In another embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 5 and 35 μm, and the span is between 0 and 1.9, preferably between 0 and 1.5, more preferably between 0 and 1, even more preferably between 0 and 0.5, such as between 0 and 0.2 or between 0 and 0.1.

[0101] In another embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 1 and 35 μm, and the span is between 0 and 1.9, preferably between 0 and 1.5, more preferably between 0 and 1, even more preferably between 0 and 0.5, such as between 0 and 0.2 or between 0 and 0.1.

[0102] In yet another preferred embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 10 and 25 μm, and the span is between 0 and 1.9, preferably between 0 and 1.5, more preferably between 0 and 1, even more preferably between 0 and 0.5, such as between 0 and 0.2 or between 0 and 0.1.

[0103] In yet another preferred embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 1 and 25 μm, and the span is between 0 and 1.9, preferably between 0 and 1.5, more preferably between 0 and 1, even more preferably between 0 and 0.5, such as between 0 and 0.2 or between 0 and 0.1.

[0104] In yet another preferred embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 1 and 15 μm, and the span is between 0 and 1.9, preferably between 0 and 1.5, more preferably between 0 and 1, even more preferably between 0 and 0.5, such as between 0 and 0.2 or between 0 and 0.1.

[0105] In yet another preferred embodiment, the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 1 and 10 μm, and the span is between 0 and 1.9, preferably between 0 and 1.5, more preferably between 0 and 1, even more preferably between 0 and 0.5, such as between 0 and 0.2 or between 0 and 0.1.

[0106] As understood by those skilled in the art, a span of 0 corresponds to a monodisperse spherical glass bead.

[0107] In a preferred embodiment, at least a portion of the hemisphere of the spherical glass bead is coated with a light-reflective coating, preferably an aluminum hemisphere coating (HAC). In another embodiment, particularly suitable for compositions based on organic solvents, at least a portion of the spherical glass bead is chemically coated with fluorine. In another embodiment, particularly suitable for water-based aqueous compositions, at least a portion of the spherical glass bead is coated with silane. In another embodiment, particularly suitable for water-based aqueous compositions, at least a portion of the spherical glass bead is coated with silicone.

[0108] In a very preferred embodiment, the amount of spherical glass beads is 10% to 50% by weight, based on the total weight of the reflective ink, coating or paint composition.

[0109] In a preferred embodiment, the amount of spherical glass beads is 15% to 50% by weight, more preferably 20% to 48% by weight, and even more preferably 25% to 45% by weight, based on the total weight of the reflective ink, coating or paint composition.

[0110] In an embodiment, the amount of spherical glass beads is 20% to 50% by weight, 20% to 49% by weight, 20% to 48% by weight, 20% to 47% by weight, 20% to 46% by weight, 20% to 45% by weight, or 20% to 44% by weight, based on the total weight of the reflective ink, coating, or paint composition.

[0111] In other embodiments, the amount of spherical glass beads is 1% to 80% by weight, 1% to 78% by weight, 1% to 76% by weight, 1% to 74% by weight, 1% to 72% by weight, 1% to 70% by weight, or 1% to 68% by weight, based on the total weight of the reflective ink, coating, or paint composition.

[0112] In other embodiments, the amount of spherical glass beads is 22% to 50% by weight, 23% to 50% by weight, 24% to 50% by weight, 25% to 50% by weight, 26% to 50% by weight, 27% to 50% by weight, or 28% to 50% by weight, based on the total weight of the reflective ink, coating, or paint composition.

[0113] In other embodiments, the amount of spherical glass beads is 2% to 85% by weight, 5% to 85% by weight, 8% to 85% by weight, 10% to 85% by weight, 12% to 85% by weight, 14% to 85% by weight, or 16% to 85% by weight, based on the total weight of the reflective ink, coating, or paint composition.

[0114] The specific application of the retroreflective ink, coating, or paint composition determines the optimal refractive index of the spherical glass beads. If the composition is to be applied in a dry environment or to a substrate that exhibits retroreflection under dry conditions, and the applied layer of the retroreflective spherical glass beads is not coated with another layer, the refractive index of the spherical glass beads, measured at a wavelength λ of 589 nm, can be between 1.8 and 2.8.

[0115] In an embodiment, the reflective ink, coating, or paint composition as defined herein comprises spherical glass beads with a refractive index between 1.8 and 2.0 as measured at a wavelength λ of 589 nm.

[0116] On the other hand, if the composition is to be applied in a humid environment or to a substrate that exhibits retroreflection under humid conditions, or if the applied layer of retroreflective spherical glass beads is coated with one or more other transparent layers, the refractive index of the spherical glass beads, measured at a wavelength λ of 589 nm, is preferably between 2.0 and 2.8, more preferably between 2.2 and 2.4. Compositions exhibiting retroreflection under both dry and humid conditions, wherein the applied layer of retroreflective spherical glass beads is coated with one or more other transparent layers or uncoated, may contain different types of glass beads with different refractive indices and optionally different sizes. In embodiments, retroreflective ink, coating, or paint compositions as defined herein contain spherical glass beads with a refractive index measured at a wavelength λ of 589 nm between 2.0 and 2.8, preferably between 2.2 and 2.4.

[0117] In another embodiment, the reflective ink, coating, or paint composition as defined herein comprises at least two types of spherical glass beads, wherein at least one type of spherical glass beads has a refractive index between 1.8 and less than 2.0 when measured at a wavelength λ of 589 nm, and at least one other type of spherical glass beads has a refractive index between 2.0 and 2.8 when measured at a wavelength λ of 589 nm.

[0118] Thickener

[0119] Reflective ink, coating, or paint compositions contain thickeners. Without being bound by any theory, it is believed that thickeners limit or reduce the settling and / or precipitation of spherical glass beads and optionally selected other particulate matter such as pigment flakes and particles in the composition, allowing the composition to be easily resuspended. Furthermore, also without being bound by any theory, it is believed that thickeners provide reflective ink, coating, or paint compositions exhibiting shear-dilution behavior.

[0120] In one embodiment, the thickener comprises a mixture of different thickeners. In other embodiments, the thickener consists of a single thickener.

[0121] The amount of solvent in a reflective ink, coating, or paint composition is specified independently. If the thickener is applied, for example, in the form of a solution, suspension, or dispersion in a solvent, the amount of thickener as defined above refers to the dry weight of the thickener.

[0122] In a preferred embodiment, the amount of thickener is 0.05% to 2.3% by weight, more preferably 0.08% to 1.5% by weight, and even more preferably 0.09% to 1.25% by weight, based on the total weight of the reflective ink, coating, or paint composition.

[0123] In this embodiment, the amount of thickener is 0.05 wt% to 2.0 wt%, 0.05 wt% to 1.5 wt%, 0.05 wt% to 1.2 wt%, 0.05 wt% to 1.1 wt%, 0.05 wt% to 1.0 wt%, 0.05 wt% to 0.9 wt%, 0.05 wt% to 0.8 wt%, 0.05 wt% to 0.7 wt%, 0.05 wt% to 0.6 wt%, or 0.05 wt% to 0.55 wt%, based on the total weight of the reflective ink, coating, or paint composition.

[0124] In other embodiments, the amount of thickener is 0.10% to 2.5% by weight, 0.15% to 2.5% by weight, 0.20% to 2.5% by weight, 0.25% to 2.5% by weight, 0.35% to 2.5% by weight, 0.45% to 2.5% by weight, 0.55% to 2.5% by weight, 0.65% to 2.5% by weight, or 0.75% to 2.5% by weight, based on the total weight of the reflective ink, coating, or paint composition.

[0125] As those skilled in the art will understand, different types of solvents typically require different thickeners. Preferred thickeners for aqueous compositions and preferred thickeners for compositions based on organic solvents will be described below.

[0126] Thickener for water-based systems

[0127] A preferred group of thickeners for aqueous compositions are ASE polymers (alkaline swelling emulsions; these polymers are produced using emulsion polymerization). ASE polymers are based on a balance of hydrophilic (meth)acrylic acid monomers and hydrophobic (meth)acrylate monomers and can be supplied in liquid form with high volume solids. ASE polymers rely on changes in pH from low to high (neutralization) to initiate thickening. “Initiation” occurs by forming a polymer in a ratio of approximately 50:50 of water-soluble (meth)acrylic acid to water-insoluble (meth)acrylate. When the acid is not neutralized (low pH), the polymer is insoluble in water and does not thicken. When the acid is fully neutralized (high pH), the polymer becomes soluble and thickens. ASE polymers are supplied at low pH (< 5) and maintain a low supply viscosity (< 100 cP) at up to 35% solids. When subjected to pH of approximately 7 or higher, ASE polymers dissolve, swell, and thicken the composition through size exclusion. The degree of thickening may be related to the molecular weight of the polymer. Because their properties depend on water absorption and swelling, ASE polymers tend to have very high molecular weights, which makes them effective thickeners. The rheological profile formed by ASE polymers is typically rapidly shear-diluted (pseudoplastic), and therefore ASE polymers are well-suited for establishing high viscosity at very low shear rates.

[0128] In this embodiment, the hydrophilic monomers of the ASE polymer are selected from the group consisting of (meth)acrylic acid, maleic acid, and combinations thereof.

[0129] In another embodiment, the hydrophobic monomer of the ASE polymer is selected from the group consisting of esters of (meth)acrylic acid and C1- to C4-ols, particularly ethyl acrylate, butyl acrylate and methyl methacrylate.

[0130] In yet another preferred embodiment, the hydrophilic monomer of the ASE polymer is selected from the group consisting of (meth)acrylic acid, maleic acid and combinations thereof, and the hydrophobic monomer of the ASE polymer is selected from the group consisting of (meth)acrylic acid and esters of C1 to C4-alcohols, particularly ethyl acrylate, butyl acrylate and methyl methacrylate.

[0131] In this embodiment, the ASE polymer is a copolymer composed of: 10% to 90% by weight of repeating units based on one or more hydrophilic monomers A and 10% to 90% by weight of repeating units based on one or more hydrophobic monomers B, wherein the total amount of monomers A and B reaches 100% by weight.

[0132]

[0133] R1 and R2 are independently hydrogen or methyl and R3 is C1- to C4-alkyl.

[0134] Another preferred group of thickeners for aqueous compositions is HASE polymers (hydrophobically modified basic swelling emulsions; these polymers are produced using emulsion polymerization). HASE polymers are copolymers based on ASE polymer chemistry, established by adding one or more hydrophobic associating monomers such as acrylate and / or vinyl ester monomers to the ASE polymer composition. HASE polymers retain the pH-dependent behavior of their ASE counterparts, but in addition to their hygroscopic properties, HASE polymers also thicken via hydrophobic association. This mechanism is called associative thickening (i.e., association with any hydrophobic portion of the composition).

[0135] As described in the ASE polymer, the hydrophilic and hydrophobic monomers of the HASE polymer can be the same. Preferably, the hydrophobic associating monomer is (meth)acrylic acid with C8-C... 22 - Alcohols, (meth)acrylate monomers, and / or (substituted) vinyl alcohols and C8-C 22 - Ethyl ester monomers of alkyl acids. In another preferred embodiment, one or more hydrophobic associative monomers are selected from the group consisting of: stearyl alcohol polyether-20 methacrylate, behenyl alcohol polyether-25 methacrylate, vinyl neodecanoate and combinations thereof.

[0136] In this embodiment, the HASE polymer is a copolymer composed of: 10% to 90% by weight of the HASE polymer based on one or more repeating units of hydrophilic monomer A as defined above, 10% to 90% by weight based on one or more repeating units of hydrophobic monomer B as defined above, and 0.01% to 2% by weight based on one or more repeating units of hydrophobic associating monomer C and / or D, wherein monomers A, B, C, and D together reach 100% by weight.

[0137]

[0138] Where R4 is hydrogen or methyl, and R5 is C8- to C9-. 22 -alkyl, wherein n is an integer from 0 to 50, wherein R6 is hydrogen or methyl and wherein R7 is C8- to C6-. 22 -alkyl.

[0139] Another preferred group of thickeners for use in aqueous compositions is hydrophobically modified ethoxylated urea (HEUR) polymers. Unlike ASE or HASE type thickeners, HEUR polymers are nonionic and soluble at any pH. This solubility is due to the ethylene oxide backbone of the polymer, which is water-soluble and constitutes most of the polymer structure. Therefore, the hydrophobic portion of the HEUR polymer in the composition is required to interact with the ethylene oxide backbone to impart structure.

[0140] Examples of ASE polymers include Rheovis® 1125 (available from BASF), ACULYN™ 33; ACULYN™ 38, ACUSOIL™ 810A, ACUSOIL™ 830, ACUSOIL™ 835, ACUSOIL™ 842 (all available from Dow Chemical), and Carbopol® Aqua 30 polymer (from Lubrizol Corporation).

[0141] Examples of HASE polymers include ACULYN. TM Excel, ACRYSOL™ TT615, ACULYN™ 22; ACULYN™ 88, ACUSOL™ 801S, ACUSOL™ 805S, ACUSOL™ 820 and ACUSOL™ 823 (all available from Dow Chemical Company).

[0142] Examples of HEUR polymers include ACUSOL™ 880, ACUSOL™ 882, and ACULYN. TM 44 and ACULYN TM 46N (all available from Dow Chemical Company).

[0143] In yet another embodiment, the solvent is water or an aqueous solvent and one or more thickeners are selected from the group consisting of: ASE polymers, HASE polymers, HEUR polymers, liquid acrylic crosslinked or copolymer dispersions, acrylate crosslinked polymers, crosslinked polyacrylic polymers, crosslinked polyacrylic copolymers, nonionic liquid emulsions of modified ethylene vinyl acetate copolymer waxes, modified urea or urea-modified polyamides and combinations thereof.

[0144] In yet another embodiment, the solvent is water or an aqueous solvent and one or more thickeners are selected from the group consisting of: acrylate crosslinked polymers, crosslinked polyacrylic polymers and crosslinked polyacrylic copolymers, particularly Carbopol® polymer products from Lubrizol, such as Carbopol® AQUA SF-1 polymer, Carbopol® AQUASF-1 OS polymer and Carbopol® Aqua SF-3 polymer.

[0145] In yet another embodiment, the solvent is water or an aqueous solvent and one or more thickeners are selected from the group consisting of liquid acrylic crosslinked or copolymer dispersions.

[0146] In yet another embodiment, the solvent is water or an aqueous solvent and one or more thickeners are selected from the group consisting of: nonionic aqueous emulsions of modified ethylene vinyl acetate copolymer waxes, such as Aquatix 8421, available from BYK.

[0147] In yet another embodiment, the solvent is water or an aqueous solvent and one or more thickeners are selected from the group consisting of modified urea or urea-modified polyamides, such as Rheobyk-420, available from BYK.

[0148] In embodiments, the solvent is water or an aqueous solvent and one or more thickeners are selected from the group consisting of: ASE polymers, HASE polymers, HEUR polymers, liquid acrylic crosslinked or copolymer dispersions, acrylate crosslinked polymers, crosslinked polyacrylic polymers, crosslinked polyacrylic copolymers, nonionic liquid emulsions of modified ethylene vinyl acetate copolymer waxes, modified urea or urea-modified polyamides, and combinations thereof.

[0149] In another embodiment, the solvent is water or an aqueous solvent and one or more thickeners are selected from the group consisting of: ASE polymers, HASE polymers, HEUR polymers, liquid acrylic crosslinked or copolymer dispersions, acrylate crosslinked polymers, crosslinked polyacrylic polymers, crosslinked polyacrylic copolymers, nonionic liquid emulsions of modified ethylene vinyl acetate copolymer waxes, and combinations thereof.

[0150] In another embodiment, the solvent is water or an aqueous solvent and one or more thickeners are selected from the group consisting of: ASE polymers, HASE polymers, HEUR polymers, liquid acrylic crosslinked or copolymer dispersions, crosslinked polyacrylic polymers, crosslinked polyacrylic copolymers and combinations thereof.

[0151] In yet another embodiment, the solvent is water or an aqueous solvent, and one or more thickeners are selected from the group consisting of ASE polymers, HASE polymers, and combinations thereof. In another embodiment, the thickener is selected from the group consisting of ASE polymers and combinations thereof. In yet another embodiment, the thickener is selected from the group consisting of HASE polymers and combinations thereof.

[0152] Thickeners for organic solvent-based compositions

[0153] Examples of thickeners that can be used in organic solvent-based reflective inks, coatings, or paint compositions are preferably selected from the group consisting of: (modified) hydrogenated castor oil, clay, modified clay, calcium sulfonate complexes, organophilic layered silicates, silica gel, synthetic amorphous silica, acrylic-type gelling agents, modified cellulose materials, polyurea dispersions, urea-modified polyamide solutions, polyurethane dispersions, and combinations thereof. Examples of modified clays include BENTONE. ® LT and Bentone ® 38 (Elementis Global). Examples of silicone include HDK. ® N20 (Wacker Chemical Corporation) or AEROSIL ® (Evonik). Examples of organophilic layered silicates include Claytone 40 (Byk). An example of modified hydrogenated castor oil is Efka. ® RM 1900 (BASF). An example of hydrogenated castor oil is Efka. ® RM1920 (BASF). An example of a urea-modified nonpolar polyamide solution in isobutanol / monophenyl glycol is Rheobyk-431 (Byk). An example of a moderately polar urea-modified polyamide solution in isobutanol / solvent naphtha is Rheobyk-430 (Byk). An example of synthesizing amorphous silica is Zeothix. ® (Huber).

[0154] In a preferred embodiment, two thickeners are used in the organic solvent-based reflective ink, coating, or paint composition, preferably:

[0155] • Organophilic layered silicates and modified hydrogenated castor oil; or

[0156] • Calcium sulfonate complexes and polyurea dispersions.

[0157] Pigment flakes and granules

[0158] The reflective ink, coating or paint composition comprises synthetic pigment flakes having an average diameter between 1 μm and 75 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10, wherein the synthetic pigment flakes are selected from (A), (B), (C) or a combination thereof;

[0159] (A) A metal sheet or synthetic mica sheet, optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, MgF2, metal alloys, and rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders.

[0160] (B) A sheet comprising Al2O3, SiO2, glass, ceramic, graphite and mica flakes, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders.

[0161] (C) A sheet comprising Al2O3 flakes doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxide, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, low-valent titanium oxides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders;

[0162] In a highly preferred embodiment, the reflective ink, coating, or paint composition comprises synthetic pigment flakes selected from (A), (B), (C), or combinations thereof, having an average diameter between 5 μm and 50 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10.

[0163] In the context of synthetic pigment flakes, the term "average diameter" refers to the median particle size D50.

[0164] As understood by those skilled in the art, the term "synthetic" in "synthetic pigment flakes" means that the pigment flakes are not naturally occurring pigment flakes, but rather that they are either chemically manufactured pigment flakes or naturally occurring pigment flakes that have undergone chemical / physical treatment. One advantage of using synthetic pigment flakes is that they can produce very smooth surfaces, thereby increasing their reflective properties.

[0165] As used herein, the term "flake" or "particle" refers to a pigment shape having a large surface area and a small thickness. Typically, a flake or particle is characterized by its "aspect ratio," which is defined as the maximum dimension (i.e., the maximum diameter of the surface) divided by the minimum dimension (i.e., the thickness). As used herein, the aspect ratio of synthetic pigment flakes is at least 10, preferably at least 15, and more preferably at least 20.

[0166] In embodiments, as used herein, the aspect ratio of the synthetic pigment flakes is at least between 10 and 500, preferably between 15 and 250, and more preferably between 20 and 100.

[0167] In a preferred embodiment, the average diameter of the synthesized pigment flakes is 6-45 μm, more preferably 7-35 μm, even more preferably 8-25 μm, even more preferably 9-20 μm, and most preferably 10-16 μm.

[0168] In the embodiments, the average diameter of the synthetic pigment flakes is 1.5 μm to 65 μm, preferably 2 μm to 50 μm, more preferably 2.5 μm to 40 μm, even more preferably 3-35 μm, and most preferably 4 μm to 30 μm.

[0169] In another embodiment, the average diameter of the synthetic pigment flakes is 1 μm to 65 μm, such as 1–50 μm, 1 μm to 40 μm, 1 μm to 35 μm, 1 μm to 25 μm, 1 μm to 20 μm, 1 μm to 15 μm, or 1 μm to 13 μm.

[0170] In another embodiment, the average diameter of the pigment flakes is 1.5 μm to 75 μm, such as 3 μm to 75 μm, 5 μm to 75 μm, 7 μm to 75 μm, 9 μm to 75 μm, or 11 μm to 75 μm.

[0171] In a preferred embodiment, the thickness of the synthetic pigment flake is between 10 nm and 800 nm, more preferably between 15 nm and 600 nm. In another preferred embodiment, the thickness of the synthetic pigment flake is between 10 and 200 nm, more preferably between 10 and 150 nm, even more preferably between 10 and 100 nm, and still more preferably between 10 and 50 nm. In yet another preferred embodiment, the thickness of the synthetic pigment flake is between 200 nm and 980 nm, such as between 300 nm and 980 nm, 400 nm and 980 nm, or 500 nm and 980 nm.

[0172] The inventors have discovered that the reflective and coverage properties of inks, coatings, or paints containing pigments and reflective spherical glass beads conflict in that the amount of pigment typically required to achieve sufficient coverage is greatly reduced or even completely destroyed in terms of reflective properties.

[0173] It is known in this technology that applying pigment flakes with large, smooth surface areas to ink, paint, or coating formulations typically produces a layer with high reflectivity. Conversely, adding flakes or particles with irregular surface areas to ink, paint, or coating formulations typically produces a layer with high coverage. However, it is difficult to simultaneously achieve both high reflectivity and high coverage. A combination of sufficient reflectivity and sufficient coverage can generally be obtained using flakes with smooth surfaces (synthetic pigment flakes) and average (surface) diameters between 1 μm and 75 μm, such as those between 5 and 50 μm.

[0174] The inventors have discovered that satisfactory reflective properties and sufficient coverage properties of ink, coating, or paint layers comprising both pigments and reflective spherical glass beads can be obtained by applying pigment flakes and pigment particles of a specific limited concentration in the composition and by applying synthetic pigment flakes with a minimum concentration having an average (surface) diameter between 1 μm and 75 μm, such as between 5 and 50 μm, a thickness of less than 1 μm, and an aspect ratio of at least 10.

[0175] Not wishing to be bound by any theory, the inventors hypothesize that a ratio between 1 and 75 μm (e.g., 5 and 50 μm) of the average (surface) diameter of the synthetic pigment flakes and its smooth surface area provides sufficient coverage without unduly reducing reflectivity. Improved coverage indicates lower retroreflectivity. However, it is believed that the reflectivity of the smooth surface area of ​​the synthetic pigment flakes again improves retroreflectivity. Not wishing to be bound by any theory, the inventors further hypothesize that the very limited thickness of the synthetic pigment flakes (approximately the wavelength of visible light) further contributes to the retroreflective properties.

[0176] As those skilled in the art will understand, a high concentration of the combined amounts of synthetic pigment flakes (A), (B), and (C) and one or more pigment flakes or particles (D) results in reduced reflectivity. Conversely, a low concentration of the combined amounts of synthetic pigment flakes (A), (B), and (C) and one or more pigment flakes or particles (D) can result in reduced coverage. However, the reduced coverage due to the low concentration of the combined amounts of synthetic pigment flakes (A), (B), and (C) and one or more pigment flakes or particles (D) can be compensated for by applying a thicker layer to the substrate.

[0177] Therefore, based on the total weight of the reflective ink, coating, or paint composition, the combined amount of synthetic pigment flakes (A), (B), and (C) and one or more pigment flakes or particles (D) is between 0.20% by weight and 4.5% by weight, preferably between 0.20% and 4.0% by weight, more preferably between 0.20% and 3.5% by weight, even more preferably between 0.20% and 3.0% by weight, even more preferably between 0.20% and 2.5% by weight, and even more preferably between 0.20% and 2.0% by weight.

[0178] In a preferred embodiment, based on the total weight of the reflective ink, coating, or paint composition, the amount of one or more pigment flakes or particles (D), in addition to the synthetic pigment flakes (A), (B), and (C), is between 0 and 1.5% by weight, more preferably between 0 and 1.25% by weight, such as between 0 and 1% by weight, between 0 and 0.75% by weight, or between 0 and 0.5% by weight.

[0179] In a preferred embodiment, based on the total weight of the reflective ink, coating, or paint composition, the amount and combination amount of the synthetic pigment flakes (A), (B), and (C) are between 0.20 and 4.0% by weight, more preferably between 0.20 and 3.5% by weight, even more preferably between 0.20 and 3.0% by weight, even more preferably between 0.20 and 2.5% by weight, and even more preferably between 0.20% and 2.0% by weight.

[0180] In a preferred embodiment, the average diameter of the synthesized pigment flakes is greater than 30% of the median particle size D50 of the spherical glass beads, more preferably greater than 33%, such as greater than 35%, greater than 40%, greater than 50%, greater than 55%, greater than 60%, greater than 70%, greater than 90%, greater than 110%, or greater than 130%.

[0181] In another preferred embodiment, the average diameter of the synthesized pigment flakes is between 30% and 400% of the median particle size D50 of the spherical glass beads, more preferably between 40% and 400%, such as between 45% and 400%, 50% and 400%, 55% and 400%, 60% and 400%, 70% and 400%, 90% and 400%, 110% and 400%, or 130% and 400%.

[0182] In yet another preferred embodiment, the average diameter of the synthetic pigment flake is between 30 and 350% of the median particle size D50 of the spherical glass beads, more preferably between 30 and 300%, such as between 30 and 250%, between 30 and 225%, between 30 and 200%, between 30 and 175%, between 30 and 150%, between 30 and 125%, between 30 and 100%, or between 30 and 75%.

[0183] Example of slice (A)

[0184] The sheet (A) can have zero to multiple coating layers, such as 1, 2, 3, 4 or 5 coating layers.

[0185] In an embodiment, the metal in the sheet (A) is selected from the group consisting of aluminum, silver, and gold, preferably aluminum. In a preferred embodiment, the sheet (A) is an aluminum sheet without any coating. Examples of suitable aluminum sheets (A) without any coating include Decomet. ® Aluminum sheet (Schlenk, Germany). Decomet ® Average particle size of aluminum sheet (D) 50 The thickness is typically between 10 and 15 μm and <50 nm.

[0186] In this embodiment, sheet (A) is a synthetic mica sheet without any coating.

[0187] In this embodiment, the pigment sheet (A) is a mica sheet with a dry coating layer, such as a mica sheet coated with TiO2, Fe2O3, and SnO2. An example includes Iriodin® Silver-Grey SW pigment sheet (Merck, Germany).

[0188] In one embodiment, the metal sheet (A) is an aluminum sheet coated with at least one layer of one or more components selected from the group consisting of metal oxides, SiO2, B2O3, and GeO2. In another embodiment, the metal sheet (A) is an aluminum sheet coated with a SiO2 layer.

[0189] An example of a suitable aluminum sheet (A) coated with a SiO2 layer is Aquamet. ® Aluminum sheet (Schlenk, Germany). Aquamet ® The aluminum sheets have an average particle size between 5 μm and 50 μm and a thickness between 20 nm and 1 μm.

[0190] An example of suitable aluminum flakes (A) coated with MgF2 is SpectraFlair pigment (VIAVI Solutions Inc., USA), with an average particle size (D). 50 The thickness is between 14 and 35 μm and between 250 nm and 900 nm.

[0191] In this embodiment, the sheet (A) is coated with a SiO2 layer and an outer layer containing one or more colorants and an adhesive for fixing the one or more colorants. An example of a suitable aluminum sheet (A) coated with a SiO2 layer and an outer layer containing one or more colorants and an adhesive is the Toyal sheet (Toyo Aluminium KK, Japan). The Toyal sheet may have an average particle size of about 10 μm and a thickness of less than 1 μm, such as about 100 nm.

[0192] Examples of metal oxides that can be coated onto a metal sheet (A) are selected from the group consisting of: TiO2, ZrO2, SnO2, ZnO, MnO2, MgO, Ce2O3, Fe2O3, Fe3O4, FeTiO5, Cr2O3, CoO, CO3O4, VO2, V2O3, NiO, and combinations thereof.

[0193] US2019 / 044679A1 discloses an example of a suitable aluminum sheet (A) coated with: (i) a first layer consisting of SiO2, B2O3, MnO2, MgO, GeO2 or Al2O3, (ii) a second Fe2O3 layer on top of the first layer, and optionally (iii) a third layer of TiO2, ZrO2 or Al2O3 on top of the second layer, which is incorporated herein by reference in its entirety.

[0194] Examples of pieces (B) and (C)

[0195] Sheets (B) and (C) may have one or more coating layers, such as 2, 3, 4 or 5 coating layers.

[0196] Examples of metal oxides that can be coated onto a metal sheet (A) are selected from the group consisting of: TiO2, ZrO2, SnO2, ZnO, MnO2, MgO, Ce2O3, Fe2O3, Fe3O4, FeTiO5, Cr2O3, CoO, CO3O4, VO2, V2O3, NiO, and combinations thereof.

[0197] In one embodiment, sheet (B) comprises a small piece of glass, wherein the glass is borosilicate glass.

[0198] In a highly preferred embodiment, the sheet (B) comprises Al2O3 flakes.

[0199] In an embodiment, sheet (B) or (C) is coated with one or more layers of metal oxides, such as at least one layer of metal oxides selected from the group consisting of: TiO2, ZrO2, SnO2, ZnO, MnO2, MgO, Ce2O3, Fe2O3, Fe3O4, FeTiO5, Cr2O3, CoO, CO3O4, VO2, V2O3, NiO, and combinations thereof. In a preferred embodiment, sheet (B) or (C) is coated with one or more layers of metal oxides selected from the group consisting of TiO2, Fe2O3, Fe3O4, SnO2, ZrO2, Cr2O3, and combinations thereof, such as coating with a layer of metal oxides selected from the group consisting of TiO2, Fe2O3, and combinations thereof.

[0200] EP2799398B1 discloses an example of a sheet (B) containing Al2O3 flakes coated with different layers of metal oxide, SiO2 and organic dye as a top coating, which is incorporated herein by reference in its entirety.

[0201] US6267810B1 discloses a sheet (B) containing Al2O3 flakes coated with a metal oxide selected from the group consisting of TiO2, Fe2O3 and combinations thereof, and examples of its preparation, which are incorporated herein by reference in their entirety.

[0202] An example of a sheet (B) containing Al2O3 flakes coated with a TiO2 or Fe2O3 layer is Xirallic. ® Pigments (Merck, Germany). Xirallic ® The average particle size of the pigment is between 5 μm and 50 μm, and the thickness is up to 1 μm.

[0203] In another embodiment, sheet (B) or (C) is coated with titanium low-valent oxide (Ti). n O 2n-1 , where n is an integer greater than 1, such as oxide (Ti3O5, Ti2O3) layer, titanium oxynitride layer, FeO(OH) layer or translucent metal layer, for example containing Al, Fe, Cr, Ag, Au, Pt or Pd or combinations thereof.

[0204] In yet another embodiment, sheet (B) or (C) is coated with a metal sulfide layer, such as a sulfide coated with tungsten, molybdenum, cerium, lanthanum or rare earth elements.

[0205] In another embodiment, sheet (B) or (C) is coated with one or more colorants (e.g., Prussian Blue or Carmine Red) and an outer layer of adhesive for fixing the colorants.

[0206] As those skilled in the art will understand, these different layers can be combined, provided that one or more colorant and adhesive layers are always the outer layer in their presence.

[0207] EP0763573B1 discloses a sheet (C) comprising Al2O3 flakes doped with titanium oxide and coated with metal oxide, and examples of its manufacture, which are incorporated herein by reference in their entirety.

[0208] EP2799398B1 discloses an example of a sheet (C) containing small pieces of Al2O3 doped with TiO2, ZrO2, SiO2, SnO2, In2O3 or ZnO and coated with a metal oxide, which is incorporated herein by reference in its entirety.

[0209] Other ingredients

[0210] As described above, the reflective ink, coating, or paint composition contains 0% to 30% by weight of one or more additional ingredients. As those skilled in the art will understand, "other" ingredients are different from the additional ingredients defined in the reflective ink, coating, or paint composition. In other words, the additional ingredients do not include spherical glass beads, thickeners, solvents, pigment flakes or particles (D) and synthetic pigment flakes (A), (B), and (C).

[0211] In a preferred embodiment, one or more additional components are selected from the group consisting of: foam control agents, luminescent agents, UV absorbers, adhesives and resins, preservatives, dyes and curing initiators.

[0212] Suitable binders and resins for use in water-based or aqueous compositions and for use in organic solvent-based compositions are generally known to those skilled in the art. The binder or resin may be radiation-curable. If the binder or resin is radiation-curable, additional components may include a curing initiator, such as a photoinitiator or a thermal initiator.

[0213] In an embodiment, based on the total weight of the reflective ink, coating, or paint composition, the amount of one or more components is 0% to 25% by weight, 0% to 20% by weight, 0% to 15% by weight, 0% to 12% by weight, 0% to 10% by weight, 0% to 8% by weight, 0% to 6% by weight, or 0% to 5% by weight.

[0214] In other embodiments, the amount of one or more components is 0.1% to 20% by weight, 0.5% to 15% by weight, 1% to 12% by weight, 1.5% to 10% by weight, 2% to 8% by weight, or 2.5% to 6% by weight, based on the total weight of the reflective ink, coating, or paint composition.

[0215] The amount of solvent in a reflective ink, coating, or paint composition is specified independently. If one or more additional ingredients are applied, for example, in the form of a solution, suspension, or dispersion in a solvent, the amount of one or more additional ingredients as defined above refers to the dry weight of one or more additional ingredients, i.e., the weight excluding the solvent.

[0216] rheological behavior

[0217] Reflective ink, coating, or paint compositions exhibit shear-dilution behavior. This means that the viscosity of the composition decreases when its static / steady state is disturbed by subjecting it to a certain increased shear rate. Viscosities as defined herein are measured using a Brookfield viscometer with a #5 spindle rotating at 10 rpm at 25°C, or using a Brookfield viscometer with a #3 spindle rotating at 0.5 and 20 rpm at 25°C.

[0218] In a preferred embodiment, the viscosity of the reflective ink, coating, or paint composition, determined using a Brookfield viscometer with a #5 spindle rotating at 10 rpm at 25°C, is between 150 and 5000 mPa·s, more preferably between 200 and 2500 mPa·s, even more preferably between 220 and 1500 mPa·s, such as between 500 and 1000 mPa·s or between 220 and 750 mPa·s.

[0219] In another preferred embodiment, the first viscosity η1 of the reflective ink, coating, or paint composition, determined using a Brookfield viscometer with a #3 spindle rotating at 0.5 rpm at 25°C, is between 500 and 8000 mPa·s, and the second viscosity η2, determined using a Brookfield viscometer with a #3 spindle rotating at 20 rpm at 25°C, is at least three times lower than the first viscosity and is between 150 and 1000 mPa·s.

[0220] In another preferred embodiment, the first viscosity η1 of the reflective ink, coating, or paint composition, determined using a Brookfield viscometer with a #3 spindle rotating at 0.5 rpm at 25°C, is between 500 and 8000 mPa·s, and the second viscosity η2, determined using a Brookfield viscometer with a #3 spindle rotating at 20 rpm at 25°C, is at least three times lower than the first viscosity and is between 150 and 600 mPa·s.

[0221] In yet another preferred embodiment, the first viscosity η1 of the reflective ink, coating, or paint composition, determined using a Brookfield viscometer with a #3 spindle rotating at 0.5 rpm at 25°C, is between 2000 and 8000 mPa·s, and the second viscosity η2, determined using a Brookfield viscometer with a #3 spindle rotating at 20 rpm at 25°C, is at least four times lower than the first viscosity and is between 350 and 600 mPa·s.

[0222] Methods for preparing reflective inks, coatings, or paint compositions

[0223] Generally, the components of a reflective ink, coating, or paint composition can be added in any order. However, it is preferred to add one or more thickeners at the end of the process, at least after the spherical glass beads are added to the solvent, because it is more difficult to distribute these components evenly in the thickened composition.

[0224] In a preferred embodiment, the thickener is added after the solvent is mixed with the spherical glass beads. In another preferred embodiment, the thickener is added after mixing the solvent, glass bridge beads, synthetic pigment flakes (A), (B), (C) or combinations thereof, one or more optionally selected pigment flakes or particles (D), and any other ingredients. Stirring or homogenization is preferably carried out at a low shear rate to avoid the inclusion of air bubbles in the reflective ink, coating, or paint composition.

[0225] Method for preparing water-based or water-based retroreflective inks, coatings or paint compositions

[0226] As explained above, the thickening effect of thickeners in aqueous or water-based compositions can be pH-dependent. Therefore, methods for preparing aqueous or water-based reflective inks, coatings, or paint compositions include adjusting the pH, for example, to a value between 6.0 and 11, such as between 7.0 and 11, 7.0 and 9.5, or 7.4 and 7.9. The pH can be suitably adjusted using dilute NaOH or aminomethylpropanol neutralizers such as AMP Ultra® PC 2000.

[0227] Therefore, in embodiments, a method is provided for preparing a reflective ink, coating, or paint composition as defined herein, wherein the solvent is water or an aqueous solvent, the method comprising the following steps:

[0228] (i) Add water or an aqueous solvent, spherical glass beads as defined above, synthetic pigment flakes (A), (B), (C) as defined above, or combinations thereof, one or more optional pigment flakes or particles as defined above (D), one or more thickeners as defined above, and one or more optional additional ingredients as defined above to the container;

[0229] (ii) Preferably, the mixture obtained in step (i) is stirred or homogenized at a temperature between 15°C and 30°C, preferably for a time period between 5 and 15 minutes; and

[0230] (iii) Optionally adjust the pH before or after step (ii), preferably to a value between 6.0 and 11, more preferably to a value between 7.0 and 11, such as to a value between 7.0 and 9.5.

[0231] However, the addition of different components is also carried out at different stages of the method. Therefore, in an embodiment, a method is provided for preparing a reflective ink, coating, or paint composition as defined herein, wherein the solvent is water or an aqueous solvent, the method comprising the following steps:

[0232] (i) Add water or an aqueous solvent, spherical glass beads as defined above, at least a portion of one or more thickeners as defined above and optionally a portion of one or more additional ingredients as defined above, optionally a portion of synthetic pigment flakes (A), (B), (C) as defined above or a combination thereof and optionally a portion of one or more optional pigment flakes or particles (D) as defined above to the container;

[0233] (ii) Preferably, the mixture obtained in step (i) is stirred or homogenized at a temperature between 15°C and 30°C for a period of time between 5 minutes and 15 minutes;

[0234] (iii) Optionally adjust the pH before or after step (ii), preferably to a value between 6.0 and 11, more preferably to a value between 7.0 and 11, such as to a value between 7.0 and 9.5;

[0235] (iv) Add at least a portion of one or more additional ingredients as defined above, at least a portion of synthetic pigment flakes (A), (B), (C) or combinations thereof as defined above, and at least a portion of one or more optionally selected pigment flakes or particles (D) as defined above to the composition obtained in step (ii) or (iii), optionally add a portion of one or more thickeners as defined above, and optionally add water or an aqueous solvent.

[0236] (v) Preferably, the mixture obtained in step (v) is stirred or homogenized at a temperature between 15°C and 30°C, preferably for a time period between 5 minutes and 15 minutes; and

[0237] (vi) Optionally adjust the pH before or after step (v), preferably to a value between 6.0 and 11, more preferably to a value between 7.0 and 11, such as to a value between 7.0 and 9.5;

[0238] In the implementation, the time between steps (i) and (iii) and the time between steps (iv) and (vi) can be several days, several months or longer.

[0239] Methods for preparing water-based or water-based retroreflective ink, coating, or paint compositions may also include producing an intermediate water-based or water-based retroreflective ink, coating, or paint composition having the composition and properties as defined above, followed by adding and mixing another component to obtain a final water-based or water-based retroreflective ink, coating, or paint composition, provided that the final water-based or water-based retroreflective ink, coating, or paint composition still has the composition and properties as described above.

[0240] Therefore, in embodiments, a method is provided for preparing a reflective ink, coating, or paint composition as defined herein, wherein the solvent is water or an aqueous solvent, the method comprising the following steps:

[0241] (i) Add water or an aqueous solvent, spherical glass beads as defined above, at least a portion of one or more thickeners as defined above and optionally a portion of one or more additional ingredients as defined above, optionally a portion of synthetic pigment flakes (A), (B), (C) or d as defined above, or combinations thereof, and optionally a portion of one or more optional pigment flakes or particles (D) as defined above to a container;

[0242] (ii) The mixture obtained in step (i) is preferably stirred or homogenized at a temperature between 15°C and 30°C for a period of time between 5 and 15 minutes to obtain an intermediate retro-reflection ink, coating or paint composition having the composition and properties of a retro-reflection ink, coating or paint composition as defined above.

[0243] (iii) Optionally adjust the pH before or after step (ii), preferably to a value between 6.0 and 11, more preferably to a value between 7.0 and 11, such as to a value between 7.0 and 9.5;

[0244] (iv) Add at least a portion of one or more additional ingredients as defined above, at least a portion of synthetic pigment flakes (A), (B), (C) or combinations thereof as defined above, and at least a portion of one or more optionally selected pigment flakes or particles (D) as defined above to the intermediate retroreflective ink, coating or paint composition obtained in step (ii) or (iii), optionally adding a portion of a thickener as defined above and optionally adding water or an aqueous solvent.

[0245] (v) Preferably, the mixture obtained in step (iv) is stirred or homogenized at a temperature between 15°C and 30°C, preferably for a period of time between 5 and 15 minutes, to obtain a reflective ink, coating, or paint composition; and

[0246] (vi) Optionally adjust the pH before or after step (v), preferably to a value between 6.0 and 11, more preferably to a value between 7.0 and 11, such as to a value between 7.0 and 9.5;

[0247] In the implementation, the time between steps (i) and (iii) and the time between steps (iv) and (vi) can be several days, several months or longer.

[0248] Method for preparing organic solvent-based retroreflective inks, coatings, or paint compositions

[0249] In one embodiment, a method is provided for preparing a reflective ink, coating, or paint composition as defined herein, wherein the solvent is an organic solvent, the method comprising the following steps:

[0250] (i) adding an organic solvent, spherical glass beads as defined above, synthetic pigment flakes (A), (B), (C) or combinations thereof as defined above, one or more optionally selected pigment flakes or particles (D) as defined above, one or more thickeners as defined above, and one or more optionally selected additional ingredients as defined above to the container; and

[0251] (ii) The mixture obtained in step (i) is stirred or homogenized, preferably for a period of time between 5 and 15 minutes, preferably at a temperature between 15°C and 70°C.

[0252] In this embodiment, step (ii) is more preferably performed at a temperature between 45°C and 65°C.

[0253] However, the addition of different components is also carried out at different stages of the method. Therefore, in an embodiment, a method is provided for preparing a reflective ink, coating, or paint composition as defined herein, wherein the solvent is an organic solvent, the method comprising the following steps:

[0254] (i) Add an organic solvent, spherical glass beads as defined above, at least a portion of one or more thickeners as defined above, and optionally a portion of one or more additional ingredients as defined above, optionally a portion of synthetic pigment flakes (A), (B), (C) as defined above, or a combination thereof, and optionally a portion of one or more optional pigment flakes or particles (D) as defined above to the container.

[0255] (ii) Preferably, the mixture obtained in step (i) is stirred or homogenized at a temperature between 15°C and 70°C for a period of time between 5 minutes and 15 minutes;

[0256] (iii) Adding at least a portion of one or more additional ingredients as defined above, at least a portion of synthetic pigment flakes (A), (B), (C) or combinations thereof as defined above, and at least a portion of one or more optionally selected pigment flakes or particles (D) as defined above to the composition obtained in step (ii) or (iii), optionally adding a portion of one or more thickeners as defined above, and optionally adding an organic solvent; and

[0257] (iv) The mixture obtained in step (iii) is stirred or homogenized, preferably for a period of time between 5 and 15 minutes, preferably at a temperature between 15°C and 70°C.

[0258] In this embodiment, steps (ii) and (iv) are more preferably performed at a temperature between 45°C and 65°C. In this embodiment, the time between steps (i) and (ii) and the time between steps (iii) and (iv) can be several days, several months, or even longer.

[0259] A method for preparing a retroreflective ink, coating, or paint composition (where the solvent is an organic solvent) may also include producing an organic solvent-based retroreflective ink, coating, or paint composition having the composition and properties as defined above, followed by adding and mixing another component to obtain a final organic solvent-based retroreflective ink, coating, or paint composition, provided that the final organic solvent-based retroreflective ink, coating, or paint composition has the composition and properties as defined above.

[0260] Therefore, in embodiments, a method is provided for preparing a reflective ink, coating, or paint composition as defined herein, wherein the solvent is an organic solvent, the method comprising the following steps:

[0261] (i) Add an organic solvent, spherical glass beads as defined above, at least a portion of one or more thickeners as defined above, and optionally a portion of one or more additional ingredients as defined above, optionally a portion of synthetic pigment flakes (A), (B), (C) as defined above, or a combination thereof, and optionally a portion of one or more optional pigment flakes or particles (D) as defined above to the container.

[0262] (ii) Preferably, the mixture obtained in step (i) is stirred or homogenized at a temperature between 15°C and 70°C for a period of time between 5 and 15 minutes to obtain an intermediate retro-reflection ink, coating or paint composition having the composition and properties of a retro-reflection ink, coating or paint composition as defined above.

[0263] (iii) Adding at least a portion of one or more additional ingredients as defined above, at least a portion of synthetic pigment flakes (A), (B), (C) or combinations thereof as defined above, and at least a portion of one or more optionally selected pigment flakes or particles (D) as defined above to the intermediate reflective ink, coating, or paint composition obtained in step (ii), optionally adding a portion of a thickener as defined above, and optionally adding an organic solvent; and

[0264] (iv) The mixture obtained in step (iii) is stirred or homogenized, preferably for a period of time between 5 and 15 minutes, preferably at a temperature between 15°C and 70°C, to obtain a reflective ink, coating or paint composition.

[0265] In this embodiment, steps (ii) and (iv) are more preferably performed at a temperature between 45°C and 65°C. In this embodiment, the time between steps (i) and (ii) and the time between steps (iii) and (iv) can be several days, several months, or even longer.

[0266] Method for coating substrates

[0267] In a second aspect, the present invention relates to a method for coating a substrate with a retroreflective layer, the method comprising the following steps:

[0268] a) Provide a substrate;

[0269] b) Optionally, apply a primer layer to the substrate of step (a);

[0270] c) Optionally, but not preferably, a coloring underlayer is applied to the substrate of step (a) or the primer layer of step (b);

[0271] d) Spraying a reflective ink, coating, or paint composition as defined above onto the substrate of step (a) or the layer of step (b) or (c) in an amount provided of 0.25 and 30 g / m 2 The combined amounts of synthetic pigment flakes (A), (B), and (C) and one or more pigment flakes or particles (D);

[0272] e) Dry and cure the substrate coated with the retroreflection layer obtained in step (d); and

[0273] f) Optionally, coat the dried substrate coated with the retroreflective layer obtained in step (e) with one or more additional transparent coating layers, and then dry or cure it.

[0274] In a preferred embodiment, the reflective ink, coating, or paint composition in step (d) is provided to deliver 0.3 and 25 g / m 2 More preferably, 0.4 and 23 g / m 2 The combined amounts of synthetic pigment flakes (A), (B), and (C) and one or more pigment flakes or particles (D) are sprayed.

[0275] In a preferred embodiment, the reflective ink, coating, or paint composition in step (d) is provided to deliver 1 to 15 g / m 2 More preferably, 1 to 8 g / m 2 The combined amounts of synthetic pigment flakes (A), (B), and (C) and one or more pigment flakes or particles (D) are sprayed.

[0276] Step (d) of spraying a reflective ink, coating, or paint composition may include spraying a single layer in step (or spraying multiple layers on top of each other in subsequent spraying steps). Subsequent layers are preferably applied “wet-in-wet,” meaning that the next layer is applied over the previous layer, at least some to virtually all of the solvent evaporates from that layer, but is not (fully) cured. This means that even when subsequent layers are applied “wet-in-wet,” an intermediate drying step is applied between the application of subsequent layers.

[0277] Intermediate drying of layers based on organic solvents is typically carried out at a temperature between 20°C and 30°C for approximately 2 to 15 minutes. Intermediate drying of layers based on water or aqueous solvents is typically carried out at a temperature between 50°C and 60°C for approximately 5 to 20 minutes.

[0278] It is also possible to completely dry and cure the previous layer before applying the next layer. Complete drying and curing of organic solvent-based layers typically takes about 20 minutes at approximately 60°C. Complete drying and curing of water- or aqueous solvent-based layers typically takes about 20 minutes at approximately 60°C or overnight at ambient temperature. Choosing appropriate drying conditions is within the skill of the technician.

[0279] In an implementation, step (d) includes spraying more than one layer, such as 2, 3, 4 or 5 layers.

[0280] In an implementation, step (d) includes n subsequent spraying steps to produce n layers, wherein layer x is at least partially applied to layer x-1, where x is an integer between 2 and n, and where n is an integer between 2 and 5.

[0281] In a preferred embodiment, the reflective ink, coating, or paint composition is used in step (d) at a concentration of 200 to 800 g / m 2 The amount of substrate is more preferably 300 to 600 g / m 2 The amount of substrate applied.

[0282] In this implementation, step (b) is omitted. In this highly preferred implementation, step (c) is omitted.

[0283] The geometry of the substrate to be coated is not limited in any sense, as long as it can be coated by spraying, i.e., as long as droplets of the reflected ink, coating, or paint composition can reach the surface of the substrate. In one embodiment, the substrate is planar. In other embodiments, the substrate is curved. In other embodiments, the substrate includes planar portions and curved portions.

[0284] The inventors have determined that reflective ink, coating, or paint compositions can be applied to various substrates, for example, using industrial high-speed spraying, to produce reflective coating layers with excellent printing or coating quality, such as uniformity and reflectivity at wide angles. These results can be obtained when the reflective ink, coating, or paint composition is applied to the surface of a vertically positioned substrate, and even when the surface of the substrate is sprayed from below.

[0285] If the retroreflective coating layer is provided with one or more other transparent coating layers (i.e., step (f) of the method for coating a substrate as defined herein) is performed, a retroreflective layer with high smoothness and improved cleanability is obtained.

[0286] In a preferred embodiment, the substrate is selected from textiles, leather, metals, concrete, rubber, plastics, carbon fibers, and combinations thereof. As used herein, textiles include woven or knitted fabrics such as cotton, polyester, nylon, silk, wood, rubber fibers, and acrylic.

[0287] Regardless of the type of material the substrate is made of, the substrate can be selected from the following groups: clothing, traffic signs, car chassis or body, bicycle frame, road, road surface and guardrail.

[0288] A substrate provided with a retroreflective coating according to the invention may be provided with one or more other transparent coating layers in step (f). These one or more other transparent coating layers may be used to protect the retroreflective layer from scratches and / or moisture. Furthermore, they may be used to provide a substrate coated with a retroreflective layer having a specific matte and / or glossy / smooth appearance. The one or more other transparent coating layers may be colored. The one or more other transparent coating layers applied in an optionally selected step (f) may include a liquid coating layer, a powder coating layer, or a combination thereof that is subsequently cured or dried.

[0289] If one or more other clear coating layers are to be applied in step (f) to a layer of organic solvent-based retroreflective ink, coating, or paint composition, the layer of retroreflective ink, coating, or paint composition is typically not fully cured. If one or more other clear coating layers are to be applied in step (f) to a layer of water-based or aqueous solvent-based retroreflective ink, coating, or paint composition, the layer of retroreflective ink, coating, or paint composition is typically fully cured. Appropriate drying conditions should be selected within the skill of a technician.

[0290] The spraying in step (c) is preferably performed using a spray gun, a high-speed rotating cup, or a spray can containing propellant. In a preferred embodiment, the spraying is performed without the use of propellant.

[0291] In a third aspect, the present invention relates to a substrate coated with a retroreflective layer, which can be obtained by the method defined above. The substrate coated with the retroreflective layer can have a matte or glossy appearance.

[0292] In a preferred embodiment, a substrate coated with a retroreflective layer, preferably coated with one or more other transparent coating layers (i.e., step (e) of the method for coating the substrate as described above) displays the retroreflective layer perpendicularly to the coated substrate at an angle between 0 and 80°, such as between 0 and 78°, 0 and 75°, 0 and 70°, 0 and 65°, 0 and 60°, 0 and 55°, 0 and 50°, 0 and 45°, and 0 and 40°. The retroreflection of the retroreflective layer is determined by guiding a torch beam to the retroreflective layer (where the eye's line of sight substantially coincides with the torch beam) and by visually determining whether retroreflection is observed. The experiment begins at zero angle relative to the coated substrate, and this angle is gradually increased until retroreflection is indistinguishable.

[0293] Therefore, the present invention has been described with reference to certain embodiments discussed above. It should be recognized that these embodiments are readily adaptable to various modifications and alternative forms are well known to those skilled in the art.

[0294] Furthermore, for proper understanding of this document and its claims, the verb "to comprise" and its variations should be understood to be used without limitation, meaning to include the items following the word, but not excluding items specifically mentioned. Additionally, unless the context explicitly requires the presence of one and only one element, the indefinite article "a / an" referring to one element does not exclude the possibility of more than one element. Therefore, the indefinite article "a / an" generally means "at least one".

[0295] Example

[0296] Example 1

[0297] Six compositions (samples 1-5 and 7) and two comparative compositions (samples 6 and 8) according to the invention were prepared on a kg scale. The following ingredients were used:

[0298] Spherical glass beads:

[0299] The microglass beads (RI 2.2), obtained from Jiangxi SunflexLight Retroreflective Material Co., Ltd., have a refractive index of approximately 2.2 measured at a wavelength λ of 589 nm, a median particle size D50 of 26.56 μm, a D10 diameter of 19.77 μm, and a D90 diameter of 32.41 μm, as measured using laser diffraction, and a specific gravity of approximately 4.5 g / cm³. 3 These spherical glass beads contain TiO2, BaO, CaO, SiO2, and ZnO.

[0300] Microscopic glass beads (RI 1.9, HAC), obtained from Jiangxi Sunflex Light Retroreflective Material Co., Ltd., are hemispherical aluminum-coated glass beads with a refractive index of approximately 1.9 measured at a wavelength λ of 589 nm. The median particle size D50 is 38.22 μm, the D10 diameter is 34.86 μm, and the D90 diameter is 43.04 μm, as measured using laser diffraction. The specific gravity is approximately 4.2 g / cm³. 3 These spherical glass beads contain TiO2, BaO, SiO2, CaO, and Al2O3.

[0301] Glass beads C (with a refractive index of 2.2 measured at a wavelength of 589 nm λ) were obtained from Jiangxi Sunflex Light Retroreflective Material Co., Ltd. The median particle size (D50) of these glass beads is 40.4 μm, the D10 diameter is 37.3 μm, and the D90 diameter is 44.1 μm, as measured using laser diffraction.

[0302] solvent

[0303] Desalinated water

[0304] The solvent portion of Cromax XB155, obtained from Cromax, is a mixture of organic solvents containing xylene, toluene, ethylbenzene, isoamyl acetate, n-butyl acetate, isobutanol, 2,6-dimethyl-4-heptanone, and 2-methoxy-1-methylethyl acetate. Cromax XB383, also obtained from Cromax, contains a mixture of organic solvents such as xylene, ethylbenzene, naphtha, 1,2,4-trimethylbenzene, trimethylbenzene, n-propylbenzene, isoamyl acetate, n-butyl acetate, 2-methylbutyl acetate, and 4-methyl-2-pentanone.

[0305] The solvent portion of Syrox S900 (adhesive) is obtained from Axalta Coating Systems.

[0306] The solvent portion of Syrox S941 (diluent) is obtained from Axalta Coating Systems.

[0307] Other ingredients

[0308] AMP Ultra PC 2000, obtained from Angus Chemical Company; neutralizing agent

[0309] Acticide MBL, obtained from Thor; preservative

[0310] Aquabase Nexa P990-8999, available from PPG Industries, water-soluble adhesive.

[0311] The adhesive part of Cromax XB155

[0312] The solid component of Syrox S900 (adhesive), obtained from Axalta Coating Systems.

[0313] The solid portion of Syrox S941 (diluent), obtained from Axalta Coating Systems.

[0314] Thickener

[0315] Efka RM1900, obtained from BASF, is a modified hydrogenated castor oil thickener.

[0316] Claytone 40, derived from Rheo, is an organophilic layered silicate and a thickener.

[0317] ACULYN Excel, obtained from Dow Chemical, HASE thickener

[0318] Pigment particles and flakes

[0319] • Decomet® 1050 / 10 VP / 13974, from Schlenk Metallic Pigments GmbH, aluminum sheet with an average diameter of approximately 12-15 μm and a thickness of <50 nm.

[0320] • Toyal EMRS-D710, obtained from TOYO ALUMIMNIUM KK, aluminum sheet with an average diameter of approximately 10 μm and a thickness of <200 nm.

[0321] • Aquamet® CP-BG / 8500 / 60, available from Schlenk Metallic Pigments GmbH, is a silica-coated aluminum sheet with an average diameter of approximately 16 μm and a thickness of < 1 μm.

[0322] • Xirallic® T61-10 WNT Micro Silver, sourced from Merck KGaA, is a coated alumina sheet with an average diameter between 8 and 14 μm and a thickness of < 1 μm.

[0323] • Metal powder - PO6690 Silver, obtained from Deco Colors Holland BV, aluminum flakes, with an average diameter between 12 and 16 μm.

[0324] • Iriodin® 9602 Silver-Grey SW (sheets) are available from Merck Performance Materials Germany GmbH. These sheets are coated with mica sheets with an average diameter (D50, laser diffraction) of 22.3 μm, a thickness of less than 1 μm, and an aspect ratio (sheet diameter / thickness) of at least 10.

[0325] • Iriodin® 9612 Silver-Grey Fine Satin SW (sheets) are available from Merck PerformanceMaterials Germany GmbH. These sheets are coated with mica sheets with an average diameter (D50, laser diffraction) of 7.2 μm, a thickness of less than 1 μm, and an aspect ratio (sheet diameter / thickness) of at least 10.

[0326] Three compositions based on organic solvents according to the invention (samples 1-3) were prepared by adding the ingredients to the container in the following order:

[0327] (1) Add the organic solvent Cromax XB383 at ambient temperature (approximately 20°C);

[0328] (2) Add glass beads and mix at ambient temperature (approximately 20°C);

[0329] (3) Add Claytone 40 and mix at 1400 rpm and continue mixing at 1400 rpm at ambient temperature (approximately 20°C) for 10 minutes;

[0330] (4) Add Efka RM1900 and mix at 1800 rpm, start heating to 60°C and continue mixing at 1800 rpm for 15 minutes;

[0331] (5) Continue mixing at 1800 rpm and 60°C for 15 minutes;

[0332] (6) Cool the mixture obtained in step (5) to ambient temperature (approximately 20-25°C); and

[0333] (7) Add Cromax XB155 and pigment chips, and mix at 1800 rpm for 10 minutes.

[0334] Three compositions (samples 4, 5, and 7) and two comparative compositions (samples 6 and 8) based on water as a solvent according to the invention were prepared by adding the components to a container in the following order at ambient temperature (approximately 20°C):

[0335] (1) Add demineralized water;

[0336] (2) Add Acticide MBL and mix at 600 rpm for 10 minutes.

[0337] (3) Add glass beads while mixing at 800 rpm and continue mixing at 800 rpm for 5 minutes;

[0338] (4) Add AMP Ultra PC 2000 while mixing at 800 rpm and continue mixing at 800 rpm for 10 minutes to establish a pH of approximately 10.5;

[0339] (5) Add ACULYN Excel, and mix at 2400 rpm for 10 minutes; and

[0340] (6) Add Aquabase Nexa P990-8999, pigment flakes and deionized water, and mix at 1800 rpm for 10 minutes.

[0341] The amounts of the different components are listed in Table 1.

[0342] Table 1

[0343]

[0344] Example 2

[0345] The stability of the six reflective ink, coating, or paint compositions according to the present invention and the two comparative compositions described in Example 1 can be determined by visually and tactilely examining the samples after several days to determine whether precipitation, condensation, and separation (phase or other forms) are observed. See Table 2. Samples are considered stable if no precipitation, condensation, or separation can be observed during visual and tactile examination. Samples are considered spray-stable if they are sprayed without premixing.

[0346] Table 2

[0347]

[0348] Example 3

[0349] According to the present invention, six reflective ink, coating, or paint compositions and two comparative compositions described in Example 1 were applied at ambient temperature (approximately 20°C) using a spray gun with a 1.3 mm nozzle (DeVILBISS HVLP, DV1-C1 Plus) to a planar gray metal test plate (10.5 x 14.9 cm, effective surface area 154.2 cm²) having vertical black stripes (0.3 cm wide) spanning the entire surface. 2 ).

[0350] Two types of layers are applied: a "normal layer" and a "fog layer." For the "normal layer," the spray gun is positioned 30 cm away from the metal test panel and a pressure of 1.8 bar is applied. For the "fog layer," the spray gun is positioned 50 cm away from the metal test panel and a pressure of 1.3 bar is applied. Good results can be obtained when the test panel is sprayed horizontally or vertically from above or below.

[0351] Subsequent layers are applied using a "wet-in-wet technique," meaning that each subsequent layer is applied over the previous one, at least some to virtually all of the solvent evaporates from that layer, but it is not (fully) cured. This implies a drying time between the application of subsequent layers. Intermediate drying of organic solvent-based layers is carried out at a temperature between 50°C and 60°C for approximately 10 minutes. Intermediate drying of water-based or aqueous solvent-based layers is carried out at a temperature between 50°C and 60°C for approximately 10 minutes.

[0352] The weight of the untreated metal plate is used as a reference. The weight of the treated metal plate is measured after each individual layer is applied and after intermediate drying. For these types, the amount of pigment flakes applied to the metal plate [g / m] can be calculated. 2 Given that virtually all solvents evaporate during the drying step, the amount of composition applied to the metal plate can be further calculated [g / m]. 2 In Example 3.1, a normal layer is applied. In Example 3.2, a normal layer and a fog layer are applied. In Example 3.3, two normal layers and a fog layer are applied. Finally, in Example 3.4, three normal layers and a fog layer are applied.

[0353] After complete drying and curing (i.e., 20 minutes at 60°C), the general (off-center) retroreflection and coverage of the coated substrate were visually inspected and evaluated. Additionally, the maximum retroreflection angle [°] was determined by guiding a torch beam to the retroreflection layer (where the eye's line of sight substantially coincided with the torch beam) and visually confirming whether retroreflection was observed. The experiment began at zero angle relative to the coated substrate, and this angle was gradually increased until retroreflection was indistinguishable.

[0354] A "-" designation indicates very poor coverage, and a "++++" designation indicates very good coverage. Very good coverage means the surface has a uniform color and that the vertical black bars on the test plate are not visible under normal illumination conditions or under torch light when tested with retroreflection. A "+" score is considered insufficient. Details are presented in Table 3.

[0355] Table 3

[0356]

[0357] From Table 3, Example 3.1, it can be inferred that applying a single normal layer of the composition according to the invention is generally insufficient. Only Sample 4 according to the invention provides sufficient results. As expected, the coverage of the comparative compositions (Samples 6 and 8) containing high concentrations of pigment flakes is sufficient. However, the retroreflectivity of Samples 6 and 8 is significantly insufficient. Therefore, even the retroreflection angle of Sample 6 cannot be determined.

[0358] As can also be inferred from Examples 3.2-3.4 in Table 3, applying additional layers improved coverage (due to the application of higher amounts [g / m²]). 2 The pigment flakes of the samples unexpectedly improved the reflectivity of the compositions according to the invention (samples 1-5 and 7). However, the reflectivity of samples 6 and 8 remained significantly insufficient when other layers were applied.

[0359] Table 3 shows that by selecting appropriate amounts of layers or layer thicknesses, the compositions according to the present invention can always achieve good or even very good coverage and reflectivity, thereby producing sufficiently high [g / m] content. 2 The pigment flakes have the dimensions specified above. When using comparative compositions (samples 6 and 8) containing high concentrations of pigment flakes with the dimensions specified above, this unique combination of good coverage and reflectivity could not be obtained. It was also found that the synthetic pigment flakes and spherical glass beads synergistically produce coverage.

[0360] Example 4

[0361] The viscosities of the compositions in Table 1 of Example 1 were measured using a Brookfield viscometer with a #5 spindle rotating at 10 rpm at approximately 25°C, and with a Brookfield viscometer with a #3 spindle rotating at 0.5 and 20 rpm at approximately 25°C. The results are given in Tables 5 and 6. As shown in Table 6, the reflective ink, coating, or paint compositions and the comparative compositions exhibited shear-dilution behavior.

[0362] Table 5: Brookfield viscosity at approximately 25°C using #5 spindles rotating at 10 rpm.

[0363]

[0364] Table 6: Brookfield viscosity at approximately 25°C using #3 spindle

[0365]

[0366] Example 5

[0367] Two compositions (Sample 9 and Sample 10) were prepared, differing only in the size of the synthesized pigment flakes.

[0368] The composition (by weight percentage) is as indicated in Table 7 (where the liquid portion of the components is aggregated under “solvent” and the weight percentage of the remaining components is expressed as their solid fraction).

[0369] Table 7

[0370]

[0371] Both compositions contain synthetic pigment flakes of the same concentration and type. The displacement difference between the two compositions is the diameter of the synthetic pigment flakes. In Sample 9, the ratio (%) of the average synthetic pigment flake diameter to the median diameter of the spherical glass beads is 56%, while in Sample 10 this ratio is 18%.

[0372] Both compositions were applied at ambient temperature (approximately 20°C) using a 1.2 mm nozzle (DV1.2 Mini) spray gun to a flat gray metal test plate (10.5 x 14.9 cm) spanning a surface with vertical black stripes (0.3 cm wide). Two types of layers were applied: a "normal layer" and a "fog layer". For the "normal layer", the spray gun was positioned 30–40 cm from the metal test plate and a pressure of 2.0 bar was applied. For the "fog layer", the spray gun was positioned 40–50 cm from the metal test plate and a pressure of 1.5 bar was applied. The fog layer consisted of very thin droplets (i.e., not a complete layer) applied first to improve adhesion.

[0373] Drying is performed between the application of subsequent “normal layers”. Both compositions are applied as a fog layer to a gray metal test plate, followed by drying of the fog layer on top of a subsequent normal layer, then drying, and then applying a clear top coat again, followed by drying [“single layer”, coatings (b) and (d)]. Both compositions are also applied as a fog layer and two subsequent normal layers to another gray metal test plate, subjected to intermediate and final drying, and then applied a clear top coat again, followed by drying [“multilayer”, coatings (a) and (c)].

[0374] Visually inspect the general (non-central) reflectivity and coverage of the coated substrate. The coverage of the coating layer is assessed by checking whether the surface has a uniform color and by checking that the vertical black bars on the test board are not visible under normal lighting conditions (sunlight) and are also not visible under torch light ("flash") applied to test reflectivity.

[0375] Figure 1 The coverage of the coating layers under normal lighting conditions is shown. It is clear that larger synthetic pigment flakes produce better coverage, especially when more than one layer is applied. In coating (a), the vertical black bars are barely noticeable. Figure 2Coverage and retroreflectivity under torch light (“flash”) are shown. Again, it is clear that larger synthetic pigment flakes produce better coverage, especially when more than one layer is applied. In coating (a), the vertical black bars are barely noticeable, even under torch light. Furthermore, retroreflectivity is unexpectedly better for larger synthetic pigment flakes. Thus, the ratio of a larger synthetic pigment flake diameter to the diameter of the spherical glass bead unexpectedly produces a combination of good coverage and improved retroreflectivity.

Claims

1. A retroreflective composition, comprising, based on the total weight of the composition, the following: • 15-75% by weight of solvent; • 1% to 80% by weight of spherical glass beads, wherein the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 1 μm and 150 μm, and the refractive index, as measured at a wavelength λ of 589 nm, is between 1.5 and 2.

8. • 0.05% to 2.5% by weight of one or more thickeners; as well as • 0.20% to 4.5% by weight of synthetic pigment flakes, wherein the average diameter of the synthetic pigment flakes is between 1 μm and 75 μm, the thickness is less than 1 μm, and the flake diameter / thickness ratio is at least 10, wherein the synthetic pigment flakes are selected from synthetic pigment flakes (A), (B), (C) or combinations thereof; (A) A metal sheet or synthetic mica sheet, said metal sheet or synthetic mica sheet optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, MgF2, and rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders. (B) A sheet comprising Al2O3, SiO2, glass, ceramic, graphite and mica flakes, said sheet being coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders. (C) A sheet comprising Al2O3 flakes doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxide, the sheet being coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2 and rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; • 0% to 2% by weight of one or more pigment flakes or particles (D) other than synthetic pigment flakes (A), (B) and (C); • One or more additional components, ranging from 0% to 30% by weight, wherein the combined amount of said synthetic pigment flakes (A), (B), and (C) and said one or more pigment flakes or particles (D) is between 0.20% by weight and 4.5% by weight; and The average diameter of the synthetic pigment flakes is more than 0.3 times the median particle size D50 of the spherical glass beads.

2. The retroreflective composition of claim 1, wherein, based on the total weight of the composition, the retroreflective composition comprises the following: • 15% to 68% by weight of solvent; • 10% to 50% by weight of spherical glass beads, wherein the median particle size D50 of the spherical glass beads, as measured by laser diffraction, is between 5 and 150 μm, and the refractive index, as measured at a wavelength λ of 589 nm, is between 1.5 and 2.

8. • 0.05% to 2.5% by weight of one or more thickeners; as well as • 0.20% to 4.5% by weight of synthetic pigment flakes, wherein the average diameter of the synthetic pigment flakes is between 5 μm and 50 μm, the thickness is less than 1 μm, and the flake diameter / thickness ratio is at least 10, wherein the synthetic pigment flakes are selected from synthetic pigment flakes (A), (B), (C) or combinations thereof. (A) A metal sheet or synthetic mica sheet, said metal sheet or synthetic mica sheet optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, MgF2, and rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders. (B) A sheet comprising Al2O3, SiO2, glass, ceramic, graphite and mica flakes, said sheet being coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders. (C) A sheet comprising Al2O3 flakes doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxide, the sheet being coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium oxynitride, FeO(OH), SiO2, B2O3, GeO2 and rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; • 0% to 2% by weight of one or more pigment flakes or particles (D) other than synthetic pigment flakes (A), (B) and (C); • One or more additional components from 0% to 30% by weight, wherein the combined amount of said synthetic pigment flakes (A), (B) and (C) and said one or more pigment flakes or particles (D) is between 0.20% by weight and 4.5% by weight.

3. The retroreflection composition of claim 1 or 2, wherein the average diameter of the synthetic pigment flake is more than 0.33 times the median particle size D50 of the spherical glass beads.

4. The retroreflection composition of claim 1, wherein the refractive index of the spherical glass beads measured at a wavelength λ of 589 nm is: (i) Between 2.0 and 2.8; or (ii) Between 1.7 and 2.

1.

5. The retroreflection composition of claim 1, wherein the refractive index of the spherical glass beads measured at a wavelength λ of 589 nm is: (i) Between 2.1 and 2.4; or (ii) Between 1.8 and 2.

0.

6. The retroreflection composition of claim 1, wherein the spherical glass bead hemisphere is coated with an aluminum coating.

7. The retroreflection composition of claim 1, comprising a synthetic pigment sheet (A), wherein the synthetic pigment sheet (A) is an aluminum sheet coated with a SiO2 layer or an aluminum sheet coated with a SiO2 layer and coated with an outer layer comprising one or more colorants and binders.

8. The retroreflective composition of claim 1, comprising a synthetic pigment sheet (B), wherein the synthetic pigment sheet (B) is selected from the group consisting of: Al2O3 sheets coated with TiO2, Fe2O3, mixtures of TiO2 and Fe2O3 and combinations thereof.

9. The retroreflection composition of claim 1, comprising a synthetic pigment sheet (A), wherein the synthetic pigment sheet (A) is an uncoated aluminum sheet or an uncoated synthetic mica sheet.

10. The retroreflective composition of claim 1, wherein the solvent is water or an aqueous solvent, and wherein the one or more thickeners are selected from the group consisting of: ASE polymers, HASE polymers, HEUR polymers, liquid acrylic crosslinked or copolymer dispersions, nonionic liquid emulsions of modified ethylene vinyl acetate copolymer waxes, modified urea or urea-modified polyamides, and combinations thereof.

11. The retroreflective composition of claim 1, wherein the solvent is an organic solvent, and wherein the one or more thickeners are selected from the group consisting of: hydrogenated castor oil, clay, calcium sulfonate complexes, organophilic layered silicates, silica gel, synthetic amorphous silica, acrylic gelling agents, modified cellulose materials, polyurea dispersions, urea-modified polyamide solutions, polyurethane dispersions, and combinations thereof.

12. The retroreflective composition of claim 11, wherein two thickeners are applied.

13. The retroreflective composition of claim 1, comprising 0.20% by weight to 4.0% by weight of the synthetic pigment flakes (A), (B) and (C).

14. The retroreflective composition of claim 1, wherein one or more additional components are selected from the group consisting of adhesives and resins, preservatives, dyes, and curing initiators.

15. A method for coating a substrate with a retroreflective layer, the method comprising the steps of: a) Provide a substrate; b) Optionally, apply a primer layer to the substrate of step (a); c) Optionally, a coloring underlayer is applied to the substrate of step (a) or the primer layer of step (b); d) Spraying the retroreflective composition as described in any one of claims 1 to 14 onto the substrate of step (a) or the layer of step (b) or (c) in an amount provided of 0.25 and 30 g / m 2 The combined amounts of the synthetic pigment flakes (A), (B), and (C) and the one or more pigment flakes or particles (D); e) Dry and cure the substrate coated with the retroreflection layer obtained in step (d); and f) Optionally, coat the dried substrate obtained in step (e) with one or more additional transparent coating layers, followed by drying or curing.

16. The method of claim 15, wherein the retro-projection composition is applied to the substrate in step (d) using a spray gun, a high-speed rotating cup, a high-speed rotating disk, or a spray can with a propellant.

17. The method of claim 15 or 16, wherein step (d) comprises n subsequent spraying steps to produce n layers, wherein layer x is at least partially applied to layer x-1, wherein x is an integer between 2 and n, and wherein n is an integer between 2 and 5.

18. A substrate coated with a retroreflective layer, which can be obtained by the method of any one of claims 15 to 17.

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