Retroreflective compositions for industrial 3D spraying of large surfaces

Abstract

The present invention provides a retroreflective ink, coating or paint composition comprising, based on the total weight of the composition, 15-75% by weight of a solvent; 1-85% by weight of spherical glass beads having a median particle size D50 between 1 and 150 μm as measured using laser diffraction, and a refractive index measured at a wavelength λ of 589 nm between 1.5 and 2.8; 0.05-2.5% by weight of one or more thickeners; and 0.20-4.5% by weight of synthetic pigment flakes having an average diameter between 1 and 75 pm, a thickness of less than 1 pm and an aspect ratio of at least 10, 0-2% by weight of one or more pigment flakes or particles other than synthetic pigment flakes (D); 0-30% by weight of one or more further components, wherein the combined amount of the synthetic pigment flakes and the one or more pigment flakes or particles (D) is between 0.20 and 4.5% by weight.

Description

[Technical field]

[0001] [Field of the Invention] The present invention relates to retroreflective ink, coating or paint compositions and methods for their preparation. The present invention further relates to a process for coating a substrate having a retroreflective layer using said retroreflective ink, coating or paint compositions, and to substrates coated with a retroreflective layer obtainable by said process. [Background of the invention]

[0002] Retroreflective paints, inks and coatings are used in a variety of applications, such as to improve the visibility of road signs, road markers, fabrics, automobiles, etc., under low light conditions. Paints, inks and coatings are typically imparted with retroreflective properties by the addition of spherical glass beads having a particular refractive index. Retroreflection occurs through the tandem action of refraction of incident light through the top surface of the spherical glass bead, internal reflection from the lower inner surface of the spherical glass bead, and then refraction of the light as it exits the top surface of the spherical glass bead back in the direction from which it came.

[0003] WO 2004 / 017104 discloses a retroreflective composition comprising retroreflective microspheres, a binder system, and a thixotropic blend comprising at least two thixotropic agents in an amount of about 2 to about 5% by weight based on the retroreflective composition. The retroreflective compositions are intended for use as paints, inks, and coatings and are applied to substrates using an aerosol applicator with a propellant.

[0004] WO 01 / 16223 relates to retroreflective inks for printing on fabrics. Only one example of WO 01 / 16223 discloses a screen printing ink. Screen printing inks are not suitable for professional or industrial (high speed) spraying. In general, it is known to those skilled in the art of printing that the rheological properties of screen printing inks and inks for professional or industrial (high speed) spraying are fundamentally different, due to the fundamentally different techniques used to apply them to the substrate.

[0005] WO 00 / 42113 relates to retroreflective inks comprising microbeads in a liquid carrier medium. The inks are intended for screen printing onto fabrics.

[0006] WO 2003 / 016964 relates to a retroreflective coating system and a method of providing the coating system to a substrate, the method comprising: (a) applying a color-providing composition to a substrate, resulting in the formation of an uncured film layer of the color-providing composition; and (b) applying an at least partially transparent clearcoat composition wet-on-wet to the uncured film layer of the color-providing composition, thereby forming an uncured film layer of the clearcoat composition on the uncured film layer of the color-providing composition; wherein at least one of the color-providing composition and the clearcoat composition is crosslinkable, and at least one of the color-providing composition and the clearcoat composition includes retroreflective microspheres to provide a retroreflective coating system for a substrate. The pigmented basecoat composition includes 5 to 40 parts by weight of a pigment, such as 8 to 25 parts by weight of a flaky aluminum pigment, based on 100 parts by weight of the pigmented basecoat composition.

[0007] As generally recognized by those skilled in the art, when a substrate is coated or painted, one would like to provide the intended effect of the coating or paint over the entire surface regardless of the inhomogeneity of or on the surface of the substrate. When a substrate is provided with retroreflective properties, one would obviously like to achieve homogeneous retroreflectivity over the entire surface. Similarly, when a substrate is provided with a colored layer of coating or paint, it is required that the color difference present in the coated or painted substrate is not further visible by the colored layer of coating or paint, i.e., the colored layer of coating or paint must be sufficiently opaque. In what follows, the term "sufficiently opaque" is replaced with "having sufficient covering properties" or "having sufficient hiding power". In the context of the present invention, these three terms relate to an ink, paint or coating formulation that, when applied to a substrate, masks the color difference present on the substrate's surface. As generally known to those skilled in the art, the problem of color inhomogeneity is more prevalent for large substrates (such as, for example, a car body that needs to be painted or coated).

[0008] The inventors have discovered that the retroreflective and coverage properties of prior art coatings or paints, which contain both pigments and retroreflective spherical glass beads, are contradictory in the sense that the amount of pigment typically required to obtain sufficient coverage largely reduces or even completely destroys the retroreflective properties.

[0009] FIG. 4 of WO 2003 / 016964 discloses a coating system using an aluminum pigment, in which retroreflective microspheres are disposed in a pigmented basecoat film layer. As explained above, WO 2003 / 016964 teaches that the pigmented basecoat composition comprises 5 to 40 parts by weight, for example 8 to 25 parts by weight, of a pigment, such as a flake-like aluminum pigment, based on 100 parts by weight of the pigmented basecoat composition. As shown in the attached examples, the inventors have found that using at least 5 parts by weight of a pigment in the basecoat composition in which the retroreflective microspheres are disposed has a detrimental effect on the retroreflective properties of the basecoat film layer.

[0010] This problem can be solved by first applying a base layer containing a pigment in an amount that provides sufficient coverage, and then applying a second layer containing retroreflective spherical glass beads on top of the base layer. Figure 1 and the examples in paragraphs

[0043] -

[0046] of WO 2003 / 016964 disclose a retroreflective coating system that includes retroreflective microspheres disposed in an intermediate coat film layer between a pigmented base coat film layer and a clear coat film layer, for example. This solution, however, requires a less favorable manufacturing process in that it involves a subsequent painting or coating step with a different composition.

[0011] There is a need for retroreflective ink, coating or paint compositions that are stable on storage, yet can be easily applied to a variety of substrates, preferably using professional or industrial (high velocity) spraying, resulting in a retroreflective layer or coating that has good coverage.

[0012] It is therefore an object of the present invention to provide a retroreflective ink, coating or paint composition that has sufficient stability or shelf life and can be professionally or industrially applied to a variety of substrates, preferably using professional or industrial (high velocity) spraying.

[0013] It is a further object of the invention to provide a retroreflective ink, coating or paint composition that can be applied professionally or industrially, preferably using professional or industrial (high velocity) spraying, to a variety of substrates, resulting in a retroreflective layer or coating having good coverage.

[0014] It is yet another object of the present invention to provide a simplified method for the production of retroreflective layers having good coverage on large surfaces such as vehicle bodies, preferably using professional or industrial (high velocity) spraying.

[0015] [Summary of the invention] The inventors have unexpectedly determined that one or more of the objectives may be achieved by the use of an ink, coating or paint composition comprising retroreflective spherical glass beads and a reduced amount of pigment in the form of flakes having a particular size.

[0016] Thus, in a first aspect, the present invention provides a retroreflective ink, coating or paint composition comprising, based on the total weight of the composition: 15-75% by weight of solvent; 1 to 85% by weight of spherical glass beads having a median particle size D50 between 1 and 150 μm as measured using laser diffraction, and a refractive index between 1.5 and 2.8 as measured at a wavelength λ of 589 nm; 0.05 to 2.5% by weight of one or more thickening agents; and 0.20 to 4.5 wt. % of synthetic pigment flakes having an average diameter between 1 and 75 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10, the synthetic pigment flakes being selected from (A), (B), (C), and combinations thereof: 0-2% by weight of one or more pigment flakes or particles (D) other than the synthetic pigment flakes (A), (B) and (C); 0-30% by weight of one or more further components, (A) metal or synthetic mica flakes, optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, MgF2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (B) flakes comprising Al2O3, SiO2, glass, ceramic, graphite or mica platelets coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (C) flakes comprising Al2O3 platelets doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxides, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; A retroreflective ink, coating or paint composition is provided in which the total amount of synthetic pigment flakes (A), (B) and (C) and one or more pigment flakes or particles (D) is between 0.20 and 4.5% by weight, preferably between 0.20 and 4.0% by weight.

[0017] The inventors have found that this composition can be applied, for example, using professional or industrial (high-velocity) spraying on various substrates to provide a retroreflective coating layer with excellent coverage. Without wishing to be bound by any theory, the inventors hypothesize that synthetic pigment flakes with a specific range of average (surface) diameters between 1 and 75 μm, for example between 5 and 50 μm, and their smooth surface areas provide sufficient coverage without significantly reducing reflection. Improved coverage usually implies less retroreflectivity. However, it is believed that the reflection of the smooth surface areas of the synthetic pigment flakes still improves retroreflectivity. Without wishing to be bound by any theory, the inventors further hypothesize that the very limited thickness of the synthetic pigment flakes - on the order of the wavelength of visible light - further contributes to the retroreflective properties.

[0018] The inventors have further established that the retroreflective ink, coating or paint composition can be applied to a variety of substrates to result in a retroreflective coating layer having excellent color perception similar to that of an ink, coating or paint composition lacking retroreflective properties.

[0019] In a second aspect, the invention relates to a method of coating a substrate with a retroreflective layer, the method comprising: a) providing a substrate; b) optionally applying a primer layer to the substrate of step (a); c) optionally, but not preferably, applying a coloured base layer to the substrate of step (a) or to the primer layer of step (b); d) applying a retroreflective ink, coating or paint composition as defined above onto the substrate of step (a), or onto the layer of step (b) or (c), at a concentration of from 0.25 to 30 g / m 2 in an amount to provide a total amount of synthetic pigment flakes (A), (B) and (C), and one or more pigment flakes or particles (D); e) drying and curing the substrate coated with the retroreflective layer obtained in step (d); and f) Optionally, coating the dried substrate coated with the retroreflective layer obtained in step (e) with one or more additional transparent coating layers, followed by drying or curing.

[0020] In a third aspect, the present invention relates to a substrate coated with a retroreflective layer obtainable by the method for coating a substrate defined herein.

[0021] definition The term "shear thinning behavior" in the context of the retroreflective ink, coating or paint compositions of the present invention relates to the decrease in viscosity when the retroreflective ink, coating or paint composition, initially in a static state, is subjected to a shear rate.

[0022] As used herein, the term "pigment" refers to particulate colorants, such as globules or flakes, that are insoluble in the binder or solvent used.

[0023] As used herein, the term "dye" refers to a colorant that is molecularly soluble in the binder or solvent used.

[0024] As used herein, the term "colorant" includes pigments as well as dyes.

[0025] As used herein, the term "titanium suboxide" refers to a compound of the formula Ti n O 2n-1 In the formula, n is an integer greater than 1. [Brief description of the drawings]

[0026] [Figure 1] Demonstrates coverage of retroreflective ink, coating or paint compositions under normal lighting conditions. [Diagram 2]Demonstrates coverage and retroreflectivity of retroreflective ink, coating or paint compositions under the application of torch light ("flash"). Detailed Description

[0027] In a first aspect, the present invention provides a retroreflective ink, coating or paint composition comprising, based on the total weight of the composition: 15-75% by weight of solvent; 1 to 85% by weight of spherical glass beads having a median particle size D50 between 1 and 150 μm as measured using laser diffraction, and a refractive index between 1.5 and 2.8 as measured at a wavelength λ of 589 nm; 0.05 to 2.5% by weight of one or more thickening agents; and 0.20 to 4.5 wt. % of synthetic pigment flakes having an average diameter between 1 and 75 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10, the synthetic pigment flakes being selected from (A), (B), (C), and combinations thereof; 0-2% by weight of one or more pigment flakes or particles (D) other than the synthetic pigment flakes (A), (B) and (C); 0-30% by weight of one or more further components, (A) metal or synthetic mica flakes, optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, MgF2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (B) flakes comprising Al2O3, SiO2, glass, ceramic, graphite or mica platelets coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (C) flakes comprising Al2O3 platelets doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxides, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; The total amount of synthetic pigment flakes (A), (B) and (C) and one or more pigment flakes or particles (D) is between 0.20 and 4.5% by weight, preferably between 0.20 and 4.0% by weight, of the retroreflective ink, coating or paint composition.

[0028] In a highly preferred embodiment, a first aspect is a retroreflective ink, coating or paint composition comprising: Based on the total weight of the composition, 15-68% by weight of solvent; 10-50% by weight of spherical glass beads having a median particle size D50 between 5 and 150 μm as measured using laser diffraction, and a refractive index between 1.5 and 2.8 as measured at a wavelength λ of 589 nm; 0.05 to 2.5% by weight of one or more thickening agents; and 0.20-4.5 wt. % synthetic pigment flakes having an average diameter between 5 and 50 μm, a thickness of less than 1 μm and an aspect ratio (flake diameter / thickness) of at least 10; 0-2% by weight of one or more pigment flakes or particles (D) other than the synthetic pigment flakes (A), (B) and (C); 0-30% by weight of one or more further components, wherein the synthetic pigment flakes are selected from the group consisting of (A), (B), and (C): (A) metal or synthetic mica flakes, optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, MgF2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (B) flakes comprising Al2O3, SiO2, glass, ceramic, graphite or mica platelets coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (C) selected from flakes comprising Al2O3 platelets doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxides, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders, or combinations thereof; The total amount of synthetic pigment flakes (A), (B) and (C) and one or more pigment flakes or particles (D) is between 0.20 and 4.5% by weight, preferably between 0.20 and 4.0% by weight, of the retroreflective ink, coating or paint composition.

[0029] In a preferred embodiment, the retroreflective ink, coating or paint composition is 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, at least 2 years, and a composition is considered stable if no precipitation, syneresis or separation can be observed upon visual and tactile inspection. In a preferred embodiment, the retroreflective ink, coating or paint composition is spray stable for at least 24 hours. A composition is considered spray stable if it can be sprayed without remixing.

[0030] solvent In an embodiment, the solvent is an aqueous solvent or water. The term "aqueous solvent" as used herein refers to a solvent that comprises at least 70% water by weight, preferably at least 80% water by weight, more preferably at least 90% water by weight, even more preferably at least 95% water by weight, such as at least 96% by weight, at least 97% by weight, and at least 98% by weight, based on the weight of the aqueous solvent.The remaining solvent in the aqueous solvent is not particularly limited, but is usually a water-miscible organic solvent, for example, an alcohol (e.g., methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol, pentanol, hexanol, cyclohexanol), a polyhydric alcohol (e.g., ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, or thiodiglycol), a glycol derivative such as an ether or ester (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, dimethylformamide, N,N-dimethylformamide, or N,N-dimethylacetamide; dimethylsulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidizolidinone, acetonitrile, acetone, and combinations thereof.

[0031] In another embodiment, the solvent is an organic solvent or a mixture of organic solvents. Preferred organic solvents are selected from the group consisting of aliphatic and aromatic solvents, ketones, esters, glycoethers, alcohols, halogenated hydrocarbons, and combinations thereof. Highly preferred organic solvents are selected from the group consisting of xylene (mixture of isomers), toluene, ethylbenzene, naphtha, 1,2,4-trimethylbenzene, mesitylene, n-propylbenzene, isopentyl acetate, n-butyl acetate, (2-methoxymethylethoxy)propanol, 2-butoxyethyl acetate, 2-methylbutyl acetate, isobutanol, 1-butanol, 1-ethoxypropan-2-ol, 2,6-dimethyl-4-heptanone, 2-methoxy-1-methylethyl acetate, 4,6-dimethyl-heptan-2-one, 4-methyl-2-pentanone, 1-methoxy-2-propanol, 1-methoxy-2-propyl acetate, 2-(2-butoxyethoxy)ethanol, 2-butoxyethanol, 5-methylhexan-2-one, ethyl acetate and combinations thereof.

[0032] In a highly preferred embodiment, the amount of solvent is from 15 to 68% by weight, based on the total weight of the composition.

[0033] In embodiments, the amount of solvent is from 20 to 68 wt%, 30 to 68 wt%, 40 to 68 wt%, 50 to 68 wt%, or 52 to 68 wt%, based on the total weight of the composition.

[0034] In other embodiments, the amount of one or more additional ingredients is from 25 to 67%, 35 to 66%, or 45 to 65% by weight based on the total weight of the composition.

[0035] In embodiments, the amount of solvent is 20-75 wt%, 30-75 wt%, 40-75 wt%, 50-75 wt%, or 52-75 wt%, based on the total weight of the composition.

[0036] Spherical Glass Beads As defined above, the refractive index of the spherical glass beads measured at a wavelength λ of 589 nm lies between 1.5 and 2.8.

[0037] In a preferred embodiment, the spherical glass beads are (a) between 2.0 and 2.8, preferably between 2.1 and 2.4; or (b) a refractive index, measured at a wavelength λ of 589 nm, between 1.7 and 2.1, preferably between 1.8 and 2.0;

[0038] In a preferred embodiment, the term "glass" in "spherical glass beads" as used herein refers to an amorphous, non-crystalline solid and transparent material made of oxides. In another embodiment, the term "glass" in "spherical glass beads" refers to a solid and transparent material made of oxides and containing some microcrystallinity. The refractive index of spherical glass beads is closely related to the density of glass, but the relationship is not linear. Due to the nature of glass, the density is approximately an additive function of its composition. The density of spherical glass beads with a refractive index between 1.5 and 2.8 is typically between 2.5 and 4.5 g / cm. 3 The value fluctuates between .

[0039] Oxides which can be used in the glass are oxides of silicon, boron, aluminum, sodium, barium, vanadium, titanium, lanthanum, strontium, zirconium, potassium, magnesium, iron, calcium, zinc, lithium, barium and lead. The spherical glass beads may contain various combinations of, for example, silica (SiO2), boron oxide (BO3), phosphorus pentoxide (PO5), vanadium pentoxide (VO5), arsenic trioxide (As2O3), germanium oxide (GeO2), calcium oxide (CaO), sodium oxide (Na2O), magnesium oxide (MgO), zinc oxide (ZnO), aluminum oxide (Al2O3), potassium oxide (KO), iron oxide (Fe2O3), lead oxide (PbO), barium oxide (BaO), barium titanate (BaTiO3), titanium oxide (TiO2), lithium oxide (Li2O), strontium oxide (SrO), lanthanum oxide (La2O3), and zirconium oxide (ZrO2). Silica and boron oxide generally have the lowest density. Glasses containing a large weight percentage of these oxides therefore generally result in glass beads with a low refractive index. The refractive index can be increased by the addition of oxides with high molecular weight.

[0040] Preferably, the spherical glass beads are PbO-free.

[0041] Glass beads having a refractive index in the range of 1.5 to 2.51 and their composition in terms of oxides are disclosed in WO 2014 / 109564, which is incorporated herein by reference in its entirety. PbO-free transparent glass beads having a refractive index greater than 2.15 are disclosed in U.S. Pat. No. 4,082,427, which is incorporated herein by reference in its entirety.

[0042] The spherical glass beads may be colored spherical glass beads as long as they maintain transparency. Both colored spherical glass beads made of colored transparent glass and spherical glass beads with a concentric transparent colored coating are included in the present invention. The color may be a natural color brought about by the composition of oxides, or may be intentionally selected by adding a component with a specific color. Colored glass beads with high refractive index and high transparency are disclosed in WO2014 / 109564.

[0043] Thus, in embodiments, at least some of the spherical glass beads are made of a colored transparent glass and / or at least some of the spherical glass beads are coated with a concentric transparent colored coating.

[0044] The spherical glass beads have a median diameter D50 as measured by laser diffraction. The median diameter D50 is therefore the volume median based on the volume distribution. The median diameter D50 is the diameter below which half of the population of spherical glass beads falls. This volume median diameter is often referred to in the art as Dv50 or D v0.5 It is called.

[0045] In a highly preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, of between 5 and 150 μm.

[0046] In an embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 25 and 100 μm, preferably between 30 and 75 μm, more preferably between 35 and 50 μm.

[0047] In a preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, of between 5 and 100 μm, for example 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.

[0048] In a highly preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, of between 1 and 100 μm, for example 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.

[0049] In yet another embodiment, the spherical glass beads have a median particle size D50, as measured using laser diffraction, between 25 and 150 μm, e.g., between 50 and 150 μm, between 75 and 150 μm, between 100 and 150 μm, between 110 and 150 μm, or between 115 and 150 μm.

[0050] The diameters D10 and D90 are often referred to in the art as Dv10 or D v0.1 and Dv90 or D v0.9 The D10 diameter is the diameter below which 10% of a population of spherical glass beads fall. Similarly, the D90 diameter is the diameter below which 90% of a population of spherical glass beads fall.

[0051] The span of the particle size distribution of spherical glass beads as measured by laser diffraction is defined as follows:

[0052]

number

[0053] In another embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 15 and 100 μm, and a span 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.

[0054] In a preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 30 and 75 μm, and a span 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.

[0055] In another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 15 and 50 μm, and a span 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.

[0056] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 5 and 35 μm, and a span 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.

[0057] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 1 and 35 μm, and a span 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.

[0058] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 10 and 25 μm, and a span 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.

[0059] In yet another preferred embodiment, the spherical glass beads have a median particle size D50 measured using laser diffraction of between 1 and 25 μm and a span of 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.

[0060] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 1 and 15 μm, and a span 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.

[0061] In yet another preferred embodiment, the spherical glass beads have a median particle size D50, measured using laser diffraction, between 1 and 10 μm, and a span 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.

[0062] As will be appreciated by those skilled in the art, span=0 corresponds to monodisperse spherical glass beads.

[0063] In a preferred embodiment, at least a portion of the spherical glass beads is hemispherically coated with a light-reflecting coating, preferably with a hemispherical aluminum coating (HAC).In another embodiment, which is particularly suitable for compositions based on organic solvents, at least a portion of the spherical glass beads is fluorochemically coated.In another embodiment, which is particularly suitable for the water-based system of the aqueous composition, at least a portion of the spherical glass beads is silane-coated.In another embodiment, which is particularly suitable for the water-based system of the aqueous composition, at least a portion of the spherical glass beads is silicone-coated.

[0064] In a highly preferred embodiment, the amount of spherical glass beads is 10-50% by weight, based on the total weight of the retroreflective ink, coating or paint composition.

[0065] 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 retroreflective ink, coating or paint composition.

[0066] In embodiments, the amount of spherical glass beads is 20-50%, 20-49%, 20-48%, 20-47%, 20-46%, 20-45%, or 20-44% by weight based on the total weight of the retroreflective ink, coating, or paint composition.

[0067] In other embodiments, the amount of spherical glass beads is 1-80%, 1-78%, 1-76%, 1-74%, 1-72%, 1-70%, or 1-68% by weight, based on the total weight of the retroreflective ink, coating, or paint composition.

[0068] In other embodiments, the amount of spherical glass beads is 22-50% by weight, 23-50% by weight, 24-50% by weight, 25-50% by weight, 26-50% by weight, 27-50% by weight, or 28-50% by weight, based on the total weight of the retroreflective ink, coating, or paint composition.

[0069] In other embodiments, the amount of spherical glass beads is from 2 to 85 weight percent, 5 to 85 weight percent, 8 to 85 weight percent, 10 to 85 weight percent, 12 to 85 weight percent, 14 to 85 weight percent, or 16 to 85 weight percent, based on the total weight of the retroreflective ink, coating, or paint composition.

[0070] The particular application of the retroreflective ink, coating or paint composition will determine the optimum refractive index of the spherical glass beads. If the composition is applied in a dry environment or onto a substrate that will exhibit retroreflectivity under dry conditions, and if the applied layer of retroreflective spherical glass beads is not coated with an additional layer, the refractive index of the spherical glass beads, measured at a wavelength λ of 589 nm, may be between 1.8 and 2.8.

[0071] In an embodiment, the retroreflective ink, coating or paint composition defined herein comprises spherical glass beads having a refractive index, measured at a wavelength λ of 589 nm, between 1.8 and 2.0.

[0072] On the other hand, if the composition is to be applied in a wet environment or on a substrate that will exhibit retroreflectivity under wet conditions, or if the applied layer of retroreflective spherical glass beads is coated with one or more additional 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 that will exhibit retroreflectivity under both dry and wet conditions, and if the applied layer of retroreflective spherical glass beads is coated with one or more additional transparent layers or is uncoated, can include different types of glass beads having different refractive indices and, optionally, different sizes. In an embodiment, the retroreflective ink, coating or paint composition defined herein includes spherical glass beads having a refractive index measured at a wavelength λ of 589 nm between 2.0 and 2.8, preferably between 2.2 and 2.4.

[0073] In another embodiment, the retroreflective ink, coating or paint composition defined herein comprises at least two types of spherical glass beads, at least one type of spherical glass beads having a refractive index, measured at a wavelength λ of 589 nm, between 1.8 and less than 2.0, and at least one further type of spherical glass beads having a refractive index, measured at a wavelength λ of 589 nm, between 2.0 and 2.8.

[0074] Thickener The retroreflective ink, coating or paint composition includes a thickener. Without wishing to be bound by any theory, it is believed that the thickener limits or reduces settling and / or sedimentation of additional particulate matter, such as spherical glass beads and optionally pigment flakes and particles, in the composition, so that the composition can be easily resuspended. Furthermore, while also not wishing to be bound by any theory, it is believed that the thickener provides the retroreflective ink, coating or paint composition with shear thinning behavior.

[0075] In embodiments, the thickening agent comprises a mixture of different thickening agents, hi other embodiments, the thickening agent consists of a single thickening agent.

[0076] The amount of solvent in the retroreflective ink, coating or paint composition is specified independently. When the thickener is applied in the form of, for example, a solution, suspension or dispersion in a solvent, the amount of thickener defined above relates to the dry weight of the thickener.

[0077] In a preferred embodiment, the amount of thickener is from 0.05 to 2.3 wt %, more preferably from 0.08 to 1.5 wt %, and even more preferably from 0.09 to 1.25 wt %, based on the total weight of the retroreflective ink, coating or paint composition.

[0078] In embodiments, the amount of thickener is 0.05-2.0%, 0.05-1.5%, 0.05-1.2%, 0.05-1.1%, 0.05-1.0%, 0.05-0.9%, 0.05-0.8%, 0.05-0.7%, 0.05-0.6%, or 0.05-0.55% by weight based on the total weight of the retroreflective ink, coating, or paint composition.

[0079] In other embodiments, the amount of thickener is 0.10-2.5%, 0.15-2.5%, 0.20-2.5%, 0.25-2.5%, 0.35-2.5%, 0.45-2.5%, 0.55-2.5%, 0.65-2.5%, or 0.75-2.5% by weight based on the total weight of the retroreflective ink, coating, or paint composition.

[0080] As will be appreciated by those skilled in the art, different types of solvents typically require different thickeners. In what follows, preferred thickeners for aqueous compositions are described, as well as preferred thickeners for compositions based on organic solvents.

[0081] Thickener for water-based systems One preferred group of thickeners for aqueous compositions are ASE polymers (alkali swellable emulsions; these polymers are made using emulsion polymerization). ASE polymers are based on a balance of hydrophilic (meth)acrylic acid monomers and hydrophobic (meth)acrylate ester monomers and can be supplied at high volumetric solids in liquid form. ASE polymers rely on a change from low to high pH (neutralization) to induce thickening. The "inducer" is incorporated into the polymer by forming an approximately 50:50 ratio of water-soluble (meth)acrylic acid and water-insoluble (meth)acrylate esters. If the acid is not neutralized (low pH), the polymer is water insoluble and will not thicken. If the acid is fully neutralized (high pH), the polymer becomes soluble and thickens. ASE polymers are supplied at low pH (<5) and maintain low as-supplied viscosity (<100 cP) at up to 35% solids. When subjected to a pH of about 7 or higher, ASE polymers solubilize, swell and thicken compositions by volume exclusion. The degree of thickening can be related to the molecular weight of the polymer. ASE polymers, whose performance depends on water absorption and swelling, tend to be of very high molecular weight, which allows the polymer to thicken efficiently. The rheological profile that ASE polymers form typically exhibits rapid shear thinning (pseudoplasticity), and therefore ASE polymers are well suited to impart high viscosity at very low shear rates.

[0082] In embodiments, the hydrophilic monomer of the ASE polymer is selected from the group consisting of (meth)acrylic acid, maleic acid, and combinations thereof.

[0083] In another embodiment, the hydrophobic monomers of the ASE polymer are selected from the group consisting of esters of (meth)acrylic acid with C1-C4-alcohols, in particular ethyl acrylate, butyl acrylate and methyl methacrylate.

[0084] 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 esters of (meth)acrylic acid with C1-C4-alcohols, in particular ethyl acrylate, butyl acrylate, and methyl methacrylate.

[0085] In an embodiment, the ASE polymer is a copolymer consisting of 10-90% by weight, based on the weight of the ASE polymer, of repeat units based on one or more hydrophilic monomers A, and 10-90% by weight of repeat units based on one or more hydrophobic monomers B, the amounts of monomers A and B adding up to 100% by weight.

[0086] [ka] [wherein R1 and R2 are independently hydrogen or methyl, and R3 is C1-C4-alkyl.]

[0087] Another preferred group of thickeners for aqueous compositions are HASE polymers (hydrophobically modified alkali swellable emulsions, these polymers are produced using emulsion polymerization). HASE polymers are copolymers based on ASE polymer chemistry by adding one or more hydrophobic associative monomers, such as acrylic esters and / or vinyl ester monomers, to the ASE polymer composition. HASE polymers retain the pH-dependent behavior of their ASE counterparts, but they also thicken by hydrophobic associations in addition to water absorption. This mechanism is known as associative thickening (i.e., they associate with any hydrophobic moieties in the composition).

[0088] The hydrophilic and hydrophobic monomers of the HASE polymers may be the same as those described for the ASE polymers. Preferred hydrophobic associative monomers are (meth)acrylic acid and C8-C 22- (meth)acrylic acid ester monomers of alcohols and / or (substituted) vinyl alcohols and C8-C 22 In another preferred embodiment, the one or more hydrophobic associative monomers are selected from the group consisting of steareth-20 methacrylate, beheneth-25 methacrylate, vinyl neodecanoate, and combinations thereof.

[0089] In one embodiment, the HASE polymer is a copolymer consisting of 10-90% by weight, based on the weight of the HASE polymer, of repeat units based on one or more hydrophilic monomers A, as defined hereinbefore, 10-90% by weight of repeat units based on one or more hydrophobic monomers B, as defined hereinbefore, and 0.01-2% by weight of repeat units based on one or more hydrophobic associative monomers C and / or D, the amounts of monomers A, B, C and D adding up to 100% by weight.

[0090] [ka] [In the formula, R4 is hydrogen or methyl, and R5 is a C8-C 22 -alkyl, n is an integer from 0 to 50, R6 is hydrogen or methyl, and R7 is C8 to C 22 -alkyl.

[0091] Yet another preferred group of thickeners for aqueous compositions are hydrophobically modified ethoxylated urethane (HEUR) polymers. Unlike ASE or HASE type thickeners, HEUR polymers are non-ionic and soluble at any pH. This solubility is due to the ethylene oxide backbone of the polymer, which is water-soluble and constitutes the majority of the polymer structure. Therefore, HEUR polymers require hydrophobic moieties in the composition to interact with the ethylene oxide backbone to provide structure.

[0092] Examples of ASE polymers include Rheovis® 1125 (available from BASF Corporation), ACULYN™ 33; ACULYN™ 38, ACUSOL™ 810A, ACUSOL™ 830, ACUSOL™ 835, ACUSOL™ 842 (all available from DOW Chemical), and Carbopol® Aqua 30 polymer (manufactured by Lubrizol Corporation).

[0093] Examples of HASE polymers include ACRYSOL™ Excel, ACRYSOL™ TT615, ACRYSOL™ 22; ACRYSOL™ 88, ACRYSOL™ 801S, ACRYSOL™ 805S, ACRYSOL™ 820, and ACRYSOL™ 823 (all available from DOW Chemical).

[0094] Examples of HEUR polymers include Accusol™ 880, Accusol™ 882, Accurin™ 44, and Accurin™ 46N (all available from DOW Chemical).

[0095] In yet another embodiment, the solvent is water or an aqueous solvent and the one or more thickeners are selected from the group consisting of ASE polymers, HASE polymers, HEUR polymers, liquid acrylic crosslinked or copolymer dispersions, acrylate crosspolymers, crosslinked polyacrylic acid polymers, crosslinked polyacrylic acid copolymers, non-ionic aqueous emulsions of modified ethylene vinyl acetate copolymer waxes, modified ureas or urea modified polyamides, and combinations thereof.

[0096] In yet another embodiment, the solvent is water or an aqueous solvent and the one or more thickening agents are selected from the group consisting of acrylate crosspolymers, crosslinked polyacrylic acid polymers and crosslinked polyacrylic acid copolymers, particularly from Carbopol® polymer products from Lubrizol Corporation, such as Carbopol® AQUA SF-1 Polymer, Carbopol® AQUA SF-1 OS Polymer and Carbopol® Aqua SF-3 Polymer.

[0097] In yet another embodiment, the solvent is water or an aqueous solvent and the one or more thickening agents are selected from the group consisting of liquid acrylic crosslinked or copolymer dispersions.

[0098] In yet another embodiment, the solvent is water or an aqueous solvent and the one or more thickeners are selected from the group consisting of non-ionic aqueous emulsions of modified ethylene vinyl acetate copolymer waxes, such as Aquatix 8421 available from BYK.

[0099] In yet another embodiment, the solvent is water or an aqueous solvent and the one or more thickeners are selected from the group consisting of modified urea or urea modified polyamides, such as Rheobyk-420 available from BYK.

[0100] In an embodiment, the solvent is water or an aqueous solvent and the one or more thickeners are selected from the group consisting of ASE polymers, HASE polymers, HEUR polymers, liquid acrylic crosslinked or copolymer dispersions, acrylate crosspolymers, crosslinked polyacrylic acid polymers, crosslinked polyacrylic acid copolymers, non-ionic aqueous emulsions of modified ethylene vinyl acetate copolymer waxes, modified ureas or urea modified polyamides, and combinations thereof.

[0101] In another embodiment, the solvent is water or an aqueous solvent and the one or more thickeners are selected from the group consisting of ASE polymers, HASE polymers, HEUR polymers, liquid acrylic crosslinked or copolymer dispersions, acrylate crosspolymers, crosslinked polyacrylic acid polymers, crosslinked polyacrylic acid copolymers, non-ionic aqueous emulsions of modified ethylene vinyl acetate copolymer waxes, and combinations thereof.

[0102] In another embodiment, the solvent is water or an aqueous solvent and the 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 acid polymers, crosslinked polyacrylic acid copolymers, and combinations thereof.

[0103] In yet another embodiment, the solvent is water or an aqueous solvent, and the one or more thickeners are selected from the group consisting of ASE polymers, HASE polymers, and combinations thereof. In an embodiment, the thickener is selected from the group consisting of ASE polymers, and combinations thereof. In another embodiment, the thickener is selected from the group consisting of HASE polymers, and combinations thereof.

[0104] Thickener for organic solvent-based compositions Examples of thickeners that can be used in the organic solvent based retroreflective ink, coating or paint compositions are preferably selected from the group consisting of (modified) hydrogenated castor oil, clays, modified clays, calcium sulfonate complexes, organophilic phyllosilicates, silica gels, synthetic amorphous silicas, acrylic acid type gelling agents, modified cellulosic materials, polyurea dispersions, solutions of urea modified polyamides, polyurethane dispersions and combinations thereof. Examples of modified clays include BENTONE® LT and BENTONE® 38 (Elementis Global). Examples of silica gels include HDK® N20 (Wacker Chemical Corporation), or AEROSIL® (Evonik). Examples of organophilic phyllosilicates include Claytone 40 (Byk). An example of modified hydrogenated castor oil is Efka® RM 1900 (BASF). An example of hydrogenated castor oil is Efka RM 1920 (BASF). An example of a solution of urea modified non-polar polyamide in isobutanol / monophenyl glycol is Rheobyk-431 (Byk). An example of a solution of medium polar urea modified polyamide in isobutanol / solvent naphtha is Rheobyk-430 (Byk). An example of synthetic amorphous silica is Zeothix® (Huber).

[0105] In a preferred embodiment, in an organic solvent based retroreflective ink, coating or paint composition, two thickeners are preferably Organophilic phyllosilicates and modified hydrogenated castor oil; or A calcium sulfonate complex and a polyurea dispersion are used.

[0106] Pigment flakes and particles The retroreflective ink, coating or paint composition comprises synthetic pigment flakes having an average diameter between 1 and 75 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10, said synthetic pigment flakes being selected from (A), (B), (C) or a combination thereof: (A) metal or synthetic mica flakes, optionally coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, MgF2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (B) flakes comprising Al2O3, SiO2, glass, ceramic, graphite or mica platelets coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (C) Flakes comprising Al2O3 platelets doped with one or more components selected from the group consisting of TiO2, ZrO2, SiO2, SnO2, In2O3, ZnO and iron oxides, coated with at least one layer of one or more components selected from the group consisting of metal oxides, metals, metal sulfides, titanium suboxides, titanium oxynitrides, FeO(OH), SiO2, B2O3, GeO2, alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders.

[0107] In a highly preferred embodiment, the retroreflective ink, coating or paint composition comprises synthetic pigment flakes selected from (A), (B), (C), or combinations thereof, having an average diameter between 5 and 50 μm, a thickness of less than 1 μm, and an aspect ratio (flake diameter / thickness) of at least 10.

[0108] The term "average diameter" refers to the median particle size D50 in the context of synthetic pigment flakes.

[0109] As will be appreciated 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 are chemically manufactured pigment flakes or chemically / physically engineered naturally occurring pigment flakes. One advantage of using synthetic pigment flakes is that they have a very smooth surface, which can result in increased reflectivity.

[0110] The term "flake" or "platelet" as used herein refers to a pigment shape having a large surface area and a small thickness. Typically, flakes or platelets are characterized by their "aspect ratio", which is defined as the largest dimension (i.e., the largest diameter of the surface divided by the smallest dimension (i.e., the thickness)). Synthetic pigment flakes as used herein have an aspect ratio of at least 10, preferably at least 15, and more preferably at least 20.

[0111] In embodiments, the synthetic pigment flakes used herein have an aspect ratio between 10 and 500, preferably between 15 and 250, and more preferably between 20 and 100.

[0112] In a preferred embodiment, the average diameter of the synthetic pigment flakes is from 6 to 45 μm, more preferably from 7 to 35 μm, even more preferably from 8 to 25 μm, still more preferably from 9 to 20 μm, and most preferably from 10 to 16 μm.

[0113] In an embodiment, the average diameter of the synthetic pigment flakes is from 1.5 to 65 μm, preferably from 2 to 50 μm, more preferably from 2.5 to 40 μm, even more preferably from 3 to 35 μm, and most preferably from 4 to 30 μm.

[0114] In another embodiment, the average diameter of the synthetic pigment flakes is from 1 to 65 μm, for example from 1 to 50 μm, from 1 to 40 μm, from 1 to 35 μm, from 1 to 25 μm, from 1 to 20 μm, from 1 to 15 μm, or from 1 to 13 μm.

[0115] In another embodiment, the average diameter of the pigment flakes is from 1.5 to 75 μm, for example from 3 to 75 μm, from 5 to 75 μm, from 7 to 75 μm, from 9 to 75 μm, or from 11 to 75 μm.

[0116] In a preferred embodiment, the thickness of the synthetic pigment flakes 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 flakes is between 10 and 200 nm, more preferably between 10 and 150 nm, even more preferably between 10 and 100 nm, and even more preferably between 10 and 50 nm. In yet another preferred embodiment, the thickness of the synthetic pigment flakes 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.

[0117] The inventors have discovered that the retroreflective properties and coverage of inks, coatings or paints that contain both pigment and retroreflective spherical glass beads are contradictory in the sense that the amount of pigment normally required to obtain sufficient coverage largely reduces or even completely destroys the retroreflective properties.

[0118] It is known in the art that the application of pigment flakes with a large, smooth surface area to ink, paint or coating formulations usually results in a layer with high reflectivity. On the other hand, the addition of flakes or particles with an irregular surface area to ink, paint or coating formulations usually results in a layer with high coverage. However, it is difficult to obtain high reflectivity and high coverage at the same time. A combination of sufficient reflectivity and sufficient coverage can be obtained with flakes that usually have a smooth surface (synthetic pigment flakes) and have an average (surface) diameter between 1 and 75 μm, for example between 5 and 50 μm.

[0119] The inventors have found that satisfactory retroreflective properties and sufficient coverage of an ink, coating or paint layer containing both pigment and retroreflective spherical glass beads can be obtained by application of certain limited concentrations of pigment flakes and pigment particles in the composition, and by application of a minimum concentration of synthetic pigment flakes having an average (surface) diameter of between 1 and 75 μm, for example between 5 and 50 μm, a thickness of less than 1 μm and an aspect ratio of at least 10.

[0120] Without wishing to be bound by any theory, the inventors hypothesize that synthetic pigment flakes with a particular range of average (surface) diameters between 1 and 75 μm, for example between 5 and 50 μm, and their smooth surface areas provide sufficient coverage without significantly reducing reflection. Improved coverage implies less retroreflectivity. However, the reflection of the smooth surface areas of the synthetic pigment flakes is still believed to improve retroreflectivity. Without wishing to be bound by any theory, the inventors further hypothesize that the very limited thickness of the synthetic pigment flakes (on the order of the wavelength of visible light) further contributes to the retroreflective properties.

[0121] As will be appreciated by those skilled in the art, too high a concentration of the synthetic pigment flakes (A), (B) and (C) and the one or more pigment flakes or particles (D) will result in reduced retroreflectivity. On the other hand, too low a concentration of the synthetic pigment flakes (A), (B) and (C) and the one or more pigment flakes or particles (D) may result in reduced coverage. However, reduced coverage due to low concentrations of the synthetic pigment flakes (A), (B) and (C) and the one or more pigment flakes or particles (D) can be compensated for by applying a thicker layer to the substrate.

[0122] Thus, the combined amount of synthetic pigment flakes (A), (B) and (C) and the one or more pigment flakes or particles (D) is between 0.20 and 4.5 weight percent, preferably between 0.20 and 4.0 weight percent, more preferably between 0.20 and 3.5 weight percent, even more preferably between 0.20-3.0 weight percent, still more preferably between 0.20-2.5 weight percent, and even more preferably between 0.20-2.0 weight percent, based on the total weight of the retroreflective ink, coating or paint composition.

[0123] In preferred embodiments, the amount of one or more pigment flakes or particles (D) other than the synthetic pigment flakes (A), (B), and (C) is between 0 and 1.5 wt. %, more preferably between 0 and 1.25 wt. %, such as between 0 and 1 wt. %, between 0 and 0.75 wt. %, or between 0 and 0.5 wt. %, based on the total weight of the retroreflective ink, coating, or paint composition.

[0124] In preferred embodiments, the combined amount of synthetic pigment flakes (A), (B) and (C) is between 0.20 and 4.0 weight percent, more preferably between 0.20 and 3.5 weight percent, even more preferably between 0.20 and 3.0 weight percent, even more preferably between 0.20 and 2.5 weight percent, and even more preferably between 0.20-2.0 weight percent, based on the total weight of the retroreflective ink, coating or paint composition.

[0125] In preferred embodiments, the average diameter of the synthetic 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%.

[0126] In another preferred embodiment, the average diameter of the synthetic pigment flakes is between 30 and 400%, more preferably between 40 and 400%, such as between 45 and 400%, between 50 and 400%, between 55 and 400%, between 60 and 400%, between 70 and 400%, between 90 and 400%, between 110 and 400% or between 130 and 400% of the median particle diameter D50 of the spherical glass beads.

[0127] In yet another preferred embodiment, the average diameter of the synthetic pigment flakes is between 30 and 350%, 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% of the median particle size D50 of the spherical glass beads.

[0128] Example of thin section (A) The flakes (A) can have zero to multiple coating layers, for example 1, 2, 3, 4 or 5 coating layers.

[0129] In an embodiment, the metal in the metal flake (A) is selected from the group consisting of aluminum, silver and gold, preferably aluminum. In a preferred embodiment, the metal flake (A) is an aluminum flake without a coating. An example of a suitable aluminum flake without a coating (A) includes Decomet® aluminum flake (Schlenk, Germany). Typically, Decomet® aluminum flakes have an average particle size (D) between 10 and 15 μm. 50 ) and has a thickness of <50 nm.

[0130] In an embodiment, the flakes (A) are uncoated synthetic mica flakes.

[0131] In an embodiment, the pigment flake (A) is a mica flake having several coating layers, such as a mica flake coated with TiO2, Fe2O3, and SnO2. Examples include Iriodin® Silver-Grey SW pigment flake (Merck, Germany).

[0132] In an embodiment, the metal flake (A) is an aluminum flake coated with at least one layer of one or more components selected from the group consisting of metal oxides, SiO2, B2O3 and GeO2. In an embodiment, the metal flake (A) is an aluminum flake coated with a SiO2 layer.

[0133] An example of a suitable aluminum flake (A) coated with a SiO2 layer is Aquamet® aluminum flake (Schlenk, Germany). Aquamet® aluminum flakes typically have an average particle size between 5 and 50 μm and a thickness between 20 nm and 1 μm.

[0134] Examples of suitable aluminum flakes (A) coated with MgF2 typically have an average particle size (D) between 14 and 35 μm. 50 ), and SpectraFlair pigments (VIAVI Solutions Inc., USA) with thicknesses between 250 nm and 900 nm.

[0135] In an embodiment, the flake (A) is coated with a SiO2 layer and with an outer layer containing one or more colorants and a binder for fixing the one or more colorants. An example of a suitable aluminum flake (A) coated with a SiO2 layer and with an outer layer containing one or more colorants and a binder is Toyal flakes (Toyo Aluminium KK, Japan). Toyal flakes may have an average particle size of about 10 μm and a thickness of less than 1 μm, for example about 100 nm.

[0136] Examples of metal oxides that can be applied to the coating layer of the metal flakes (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.

[0137] Examples of suitable aluminum flakes (A) coated with (i) a first layer of SiO2, B2O3, MnO2, MgO, GeO2 or Al2O3, (ii) a second Fe2O3 layer on the first layer, and optionally (iii) a third layer of TiO2, ZrO2 or Al2O3 on the second layer are disclosed in U.S. Patent Application Publication No. 2019 / 044679, the entirety of which is incorporated herein by reference.

[0138] Examples of thin sections (B) and (C) Flakes (B) and (C) can have one to multiple coating layers, for example 2, 3, 4 or 5 coating layers.

[0139] Examples of metal oxides that can be applied to the coating layer of the metal flakes (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.

[0140] In an embodiment, flakes (B) comprise glass platelets that are borosilicate glass.

[0141] In a highly preferred embodiment, the flakes (B) comprise Al2O3 platelets.

[0142] In an embodiment, flakes (B) or (C) are coated with one or more layers of metal oxide, for example with at least one layer of metal oxide selected from the group consisting of TiO2, ZrO2, SnO2, ZnO, MnO2, MgO, Ce2O3, Fe2O3, Fe3O4, FeTiO5, Cr2O3, CoO, CO3O4, VO2, VO3, NiO and combinations thereof. In a preferred embodiment, flakes (B) or (C) are coated with one or more layers of metal oxide selected from the group consisting of TiO2, Fe2O3, Fe3O4, SnO2, ZrO2, Cr2O3 and combinations thereof, for example with one layer of metal oxide selected from the group consisting of TiO2, Fe2O3 and combinations thereof.

[0143] An example of flakes (B) comprising Al2O3 platelets coated with different layers of metal oxide, SiO2, and an organic dye as a topcoat is disclosed in EP 2799398, the entirety of which is incorporated herein by reference.

[0144] Examples of flakes (B) comprising Al2O3 platelets coated with a metal oxide selected from the group consisting of TiO2, Fe2O3, and combinations thereof, and their preparation are disclosed in U.S. Pat. No. 6,267,810, the entirety of which is incorporated herein by reference.

[0145] An example of flakes (B) containing Al2O3 platelets coated with a TiO2 or Fe2O3 layer is Xirallic® pigment (Merck, Germany). Xylallic pigments usually have an average particle size between 5 and 50 μm and a thickness of up to 1 μm.

[0146] In another embodiment, the flakes (B) or (C) are titanium suboxide (Ti n O 2n-1, n is an integer greater than 1, for example, with a layer of an oxide (Ti3O5, Ti2O3), with a layer of titanium oxynitride, with a layer of FeO(OH), or with a thin semi-transparent metal layer comprising, for example, Al, Fe, Cr, Ag, Au, Pt, or Pd, or a combination thereof.

[0147] In yet another embodiment, flakes (B) or (C) are coated with a layer of a metal sulfide, for example coated with a sulfide of tungsten, molybdenum, cerium, lanthanum or a rare earth element.

[0148] In another embodiment, flakes (B) or (C) are coated with one or more colorants, such as Prussian Blue or Carmine Red, and an outer layer of a binder for fixing the colorants.

[0149] As will be appreciated by those skilled in the art, these different layers can be combined, provided that the colorant and binder layer(s), if present, are always the outer layers.

[0150] Examples of titanium oxide-doped, metal oxide-coated Al2O3 platelet-containing flakes (C) and their fabrication are disclosed in EP 0763573, the entirety of which is incorporated herein by reference.

[0151] Examples of flakes (C) comprising platelets of Al2O3 doped with TiO2, ZrO2, SiO2, SnO2, In2O3 or ZnO and coated with metal oxides are disclosed in EP 2799398, the entirety of which is incorporated herein by reference.

[0152] Further ingredients As described above, the retroreflective ink, coating or paint composition includes 0-30% by weight of one or more additional components. As will be recognized by those skilled in the art, the "additional" components are different from the other components defined in the retroreflective ink, coating or paint composition. In other words, the additional components do not include spherical glass beads, thickeners, solvents, pigment flakes or particles (D), and synthetic pigment flakes (A), (B) and (C).

[0153] In a preferred embodiment, the further component or components are selected from the group consisting of foam control agents, luminescent agents, UV absorbers, binders and resins, preservatives, dyes and cure initiators.

[0154] Suitable binders and resins for water-based or aqueous compositions and 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, the further component may include a curing initiator, such as a photoinitiator or a thermal initiator.

[0155] In embodiments, the amount of one or more additional components is 0-25%, 0-20%, 0-15%, 0-12%, 0-10%, 0-8%, 0-6%, or 0-5% by weight, based on the total weight of the retroreflective ink, coating, or paint composition.

[0156] In other embodiments, the amount of one or more additional components is 0.1-20%, 0.5-15%, 1-12%, 1.5-10%, 2-8%, or 2.5-6% by weight, based on the total weight of the retroreflective ink, coating, or paint composition.

[0157] The amount of solvent in the retroreflective ink, coating or paint composition is specified independently. If one or more further components are applied, for example, in the form of a solution, suspension or dispersion in a solvent, the amount of the one or more further components defined above relates to the dry weight, i.e. the solvent-free weight of the one or more further components.

[0158] Rheological behavior Retroreflective ink, coating or paint compositions exhibit shear thinning behavior, meaning that the viscosity of the composition decreases when the static / stable state is disturbed by subjecting it to a certain increased shear rate. Viscosity as defined herein is measured at a temperature of 25° C. using a Brookfield viscometer with a #5 spindle rotating at 10 rpm, or at a temperature of 25° C. using a Brookfield viscometer with a #3 spindle rotating at 0.5 and 20 rpm.

[0159] In a preferred embodiment, the retroreflective ink, coating or paint composition has a viscosity of 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, as determined at a temperature of 25° C. using a Brookfield viscometer with a #5 spindle rotating at 10 rpm.

[0160] In another preferred embodiment, the retroreflective ink, coating or paint composition has a first viscosity η1, measured at a temperature of 25° C. using a Brookfield viscometer with a #3 spindle rotating at 0.5 rpm, between 500 and 8000 mPa·s, and a second viscosity η2, measured at a temperature of 25° C. using a Brookfield viscometer with a #3 spindle rotating at 20 rpm, between 150 and 1000 mPa·s, which is at most ⅓ of the first viscosity.

[0161] In another preferred embodiment, the retroreflective ink, coating or paint composition has a first viscosity η1, measured at a temperature of 25° C. using a Brookfield viscometer with a #3 spindle rotating at 0.5 rpm, between 500 and 8000 mPa·s, and a second viscosity η2, measured at a temperature of 25° C. using a Brookfield viscometer with a #3 spindle rotating at 20 rpm, that is between 150 and 600 mPa·s, which is at most ⅓ of the first viscosity.

[0162] In yet another embodiment, the retroreflective ink, coating or paint composition has a first viscosity η1, measured at a temperature of 25° C. using a Brookfield viscometer with a #3 spindle rotating at 0.5 rpm, between 2000 and 8000 mPa·s, and a second viscosity η2, measured at a temperature of 25° C. using a Brookfield viscometer with a #3 spindle rotating at 20 rpm, that is between 350 and 600 mPa·s, which is at most ¼ of the first viscosity.

[0163] Method for preparing retroreflective ink, coating or paint compositions Generally speaking, the components of the retroreflective ink, coating or paint composition can be added in any order, however, it is preferred to add the thickener(s) at the end of the process, at least after the spherical glass beads have been added to the solvent, since it is more difficult to distribute the components homogeneously in a thickened composition.

[0164] In a preferred embodiment, the thickener is added after mixing the solvent and the spherical glass beads. In another preferred embodiment, the thickener is added after mixing the solvent, the spherical glass beads, the synthetic pigment flakes (A), (B), (C) or combinations thereof, the one or more optional pigment flakes or particles (D), and any additional ingredients. Stirring or homogenization is preferably accomplished at low shear rates to avoid the inclusion of air bubbles in the retroreflective ink, coating or paint composition.

[0165] Method for preparing aqueous or water-based retroreflective ink, coating or paint compositions As explained above, the thickening effect of a thickener in an aqueous or water-based composition may depend on the value of pH. Thus, the method of preparing an aqueous or water-based retroreflective ink, coating or paint composition may include a step of adjusting the pH, for example to a value between 6.0 and 11, for example between 7.0 and 11, between 7.0 and 9.5, or between 7.4 and 7.9. The pH can be suitably adjusted using diluted NaOH or aminomethylpropanol neutralizer, for example AMP Ultra® PC 2000.

[0166] Thus, in an embodiment, there is provided a method of preparation of a retroreflective ink, coating or paint composition as defined herein, wherein the solvent is water or an aqueous solvent, said method comprising: (i) adding to a container water or an aqueous solvent, spherical glass beads as defined hereinbefore, synthetic pigment flakes (A), (B), (C) or combinations thereof as defined hereinbefore, one or more optional pigment flakes or particles (D) as defined hereinbefore, one or more thickeners as defined hereinbefore, and optionally one or more further ingredients as defined hereinbefore; (ii) stirring or homogenizing the mixture obtained in step (i) at a temperature preferably between 15 and 30° C., for a period preferably between 5 and 15 minutes; and (iii) optionally comprising, before or after step (ii), adjusting the pH, preferably to a value between 6.0 and 11, more preferably to a value between 7.0 and 11, for example to a value between 7.0 and 9.5.

[0167] However, the addition of different components may also be accomplished at different stages of the process. Thus, in embodiments, there is provided a process for the preparation of a retroreflective ink, coating or paint composition as defined herein, wherein the solvent is water or an aqueous solvent, said process comprising: (i) adding to a container water or an aqueous solvent, spherical glass beads as defined hereinbefore, at least a portion of one or more thickening agents as defined hereinbefore, optionally a portion of one or more further ingredients as defined hereinbefore, optionally a portion of synthetic pigment flakes (A), (B), (C) or a combination thereof as defined hereinbefore, and optionally a portion of one or more optional pigment flakes or particles (D) as defined hereinbefore; (ii) stirring or homogenizing the mixture obtained in step (i) at a temperature preferably between 15 and 30° C., for a period preferably between 5 and 15 minutes; (iii) optionally adjusting 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, for example to a value between 7.0 and 9.5; (iv) adding at least a portion of one or more further ingredients as defined above, at least a portion of the synthetic pigment flakes (A), (B), (C) or a combination thereof as defined above, and at least a portion of one or more optional 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 water or an aqueous solvent; (v) stirring or homogenizing the mixture obtained in step (iv) at a temperature preferably between 15 and 30° C., preferably for a period of time between 5 and 15 minutes; and (vi) optionally comprising, before or after step (v), adjusting the pH, preferably to a value between 6.0 and 11, more preferably to a value between 7.0 and 11, for example to a value between 7.0 and 9.5.

[0168] In embodiments, the time between carrying out steps (i) to (iii) on the one hand and steps (iv) to (vi) on the other hand may be several days or months, or even longer.

[0169] The method of preparing an aqueous or water-based retroreflective ink, coating or paint composition may also include the production of an intermediate aqueous or water-based retroreflective ink, coating or paint composition having the composition and properties defined above, followed by adding and mixing another composition to obtain the final aqueous or water-based retroreflective ink, coating or paint composition, provided that the final aqueous or water-based retroreflective ink, coating or paint composition still has the composition and properties defined above.

[0170] Consequently, in embodiments, there is provided a method of preparation of a retroreflective ink, coating or paint composition as defined herein, wherein the solvent is water or an aqueous solvent, said method comprising: (i) adding to a container water or an aqueous solvent, spherical glass beads as defined hereinbefore, at least a portion of one or more thickening agents as defined hereinbefore, optionally a portion of one or more further ingredients as defined hereinbefore, a portion of synthetic pigment flakes (A), (B), (C) or a combination thereof as defined hereinbefore, and optionally a portion of one or more optional pigment flakes or particles (D) as defined hereinbefore; (ii) stirring or homogenizing the mixture obtained in step (i) at a temperature preferably between 15 and 30° C., for a period preferably between 5 and 15 minutes, to obtain an intermediate retroreflective ink, coating or paint composition having the composition and properties of the retroreflective ink, coating or paint composition defined hereinbefore; (iii) optionally adjusting 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, for example to a value between 7.0 and 9.5; (iv) adding at least a portion of one or more further ingredients as defined above, at least a portion of the synthetic pigment flakes (A), (B), (C) or combinations thereof as defined above, and at least a portion of one or more optional 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; (v) stirring or homogenizing the mixture obtained in step (iv) at a temperature preferably between 15 and 30° C., for a period preferably between 5 and 15 minutes to obtain a retroreflective ink, coating or paint composition; and (vi) optionally comprising, before or after step (v), adjusting the pH, preferably to a value between 6.0 and 11, more preferably to a value between 7.0 and 11, for example to a value between 7.0 and 9.5.

[0171] In embodiments, the time between carrying out steps (i) to (iii) on the one hand, and steps (iv) to (vi) on the other hand, may be several days or months, or even longer.

[0172] Method for preparing organic solvent-based retroreflective ink, coating or paint compositions In an embodiment, there is provided a method of preparation of a retroreflective ink, coating or paint composition as defined herein, wherein the solvent is an organic solvent, said method comprising: (i) adding to a container an organic solvent, spherical glass beads as defined hereinbefore, synthetic pigment flakes (A), (B), (C) or combinations thereof as defined hereinbefore, one or more optional pigment flakes or particles (D) as defined hereinbefore, one or more thickeners as defined hereinbefore, and optionally one or more further ingredients as defined hereinbefore; and (ii) stirring or homogenizing the mixture obtained in step (i) at a temperature preferably between 15 and 70° C., for a period preferably between 5 and 15 minutes.

[0173] Step (ii) in this embodiment is more preferably carried out at a temperature between 45 and 65°C.

[0174] However, the addition of different components can also be accomplished at different stages of the process. Thus, in embodiments, there is provided a process for the preparation of a retroreflective ink, coating or paint composition as defined herein, wherein the solvent is an organic solvent, said process comprising: (i) adding to a container an organic solvent, spherical glass beads as defined above, at least a portion of one or more thickening agents as defined above, optionally a portion of one or more further ingredients as defined above, a portion of synthetic pigment flakes (A), (B), (C) or a combination thereof as defined above, and optionally a portion of one or more optional pigment flakes or particles (D) as defined above; (ii) stirring or homogenizing the mixture obtained in step (i) at a temperature preferably between 15 and 70° C., for a period preferably between 5 and 15 minutes; (iii) adding at least a portion of one or more further ingredients as defined above, at least a portion of the synthetic pigment flakes (A), (B), (C) or a combination thereof as defined above, and at least a portion of one or more optional 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 (iv) stirring or homogenizing the mixture obtained in step (iii) at a temperature preferably between 15 and 70° C., for a period preferably between 5 and 15 minutes.

[0175] Steps (ii) and (iv), in this embodiment, are more preferably carried out at a temperature between 45 and 65° C. In embodiments, the time between carrying out steps (i) and (ii), on the one hand, and steps (iii) and (iv), on the other hand, may be several days or months, or even longer.

[0176] The method of preparing a retroreflective ink, coating or paint composition in which the solvent is an organic solvent may also include the production of an intermediate organic solvent-based retroreflective ink, coating or paint composition having the composition and properties defined above, followed by adding and mixing another composition to obtain the final organic solvent-based retroreflective ink, coating or paint composition, provided that the final organic solvent-based retroreflective ink, coating or paint composition still has the composition and properties defined above.

[0177] Consequently, in embodiments, there is provided a method for the preparation of a retroreflective ink, coating or paint composition as defined herein, wherein the solvent is an organic solvent, said method comprising: (i) adding to a container an organic solvent, spherical glass beads as defined above, at least a portion of one or more thickening agents as defined above, optionally a portion of one or more further ingredients as defined above, a portion of synthetic pigment flakes (A), (B), (C) or a combination thereof as defined above, and optionally a portion of one or more optional pigment flakes or particles (D) as defined above; (ii) stirring or homogenizing the mixture obtained in step (i) at a temperature preferably between 15 and 70° C., for a period preferably between 5 and 15 minutes; obtaining an intermediate retroreflective ink, coating or paint composition having the composition and properties of the retroreflective ink, coating or paint composition defined hereinbefore; (iii) adding at least a portion of one or more further ingredients as defined above, at least a portion of the synthetic pigment flakes (A), (B), (C) or combinations thereof as defined above, and at least a portion of one or more optional pigment flakes or particles (D) as defined above to the intermediate retroreflective 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 (iv) stirring or homogenizing the mixture obtained in step (iii) at a temperature preferably between 15 and 70° C., for a period preferably between 5 and 15 minutes to obtain the retroreflective ink, coating or paint composition.

[0178] Steps (ii) and (iv) are, in this embodiment, more preferably carried out at a temperature between 45 and 65° C. In embodiments, the time between carrying out steps (i) and (ii) on the one hand, and steps (iii) and (iv) on the other, may be several days or months, or even longer.

[0179] Method for coating a substrate In a second aspect, the invention relates to a method of coating a substrate with a retroreflective layer, said method comprising: a) providing a substrate; b) optionally applying a primer layer to the substrate of step (a); c) optionally, but not preferably, applying a colored base layer to the substrate of step (a) or the primer layer of step (b); d) applying a retroreflective ink, coating or paint composition as defined above onto the substrate of step (a), or onto the layer of step (b) or (c), at a concentration of from 0.25 to 30 g / m 2 in an amount to provide a total amount of synthetic pigment flakes (A), (B) and (C), and one or more pigment flakes or particles (D); e) drying and curing the substrate coated with the retroreflective layer obtained in step (d); and f) Optionally, coating the dried substrate coated with the retroreflective layer obtained in step (e) with one or more additional transparent coating layers, followed by drying or curing.

[0180] In a preferred embodiment, the retroreflective ink, coating or paint composition is applied in step (d) at a thickness of 0.3 to 25 g / m 2 between 0.4 and 23 g / m2 The pigment flakes (A), (B) and (C) are sprayed in an amount to give a total amount of one or more pigment flakes or particles (D) between the pigment flakes (A), (B) and (C).

[0181] In another preferred embodiment, the retroreflective ink, coating or paint composition is applied in a concentration of from 1 to 15 g / m in step (d). 2 More preferably between 1 and 8 g / m 2 between 0.5 and 1.0 μg / l of the synthetic pigment flakes (A), (B) and (C), and one or more pigment flakes or particles (D).

[0182] Step (d) of spraying the retroreflective ink, coating or paint composition can include spraying a single layer in one step, or multiple layers on top of each other in subsequent spraying steps. Subsequent layers are preferably applied "wet-on-wet", meaning that the subsequent layer is applied over a previous layer that has had at least some and substantially all of the solvent evaporated, but has not (fully) cured. This means that even if the subsequent layer is applied "wet-on-wet", an intermediate drying step is applied between the application of the subsequent layer.

[0183] Intermediate drying of organic solvent based layers is usually performed at temperatures between 20 and 30° C. for about 2 to 15 minutes. Intermediate drying of water or aqueous solvent based layers is usually performed at temperatures between 50 and 60° C. for about 5 to 20 minutes.

[0184] It is also possible to thoroughly dry and cure the previous layer before applying the subsequent layer. Thorough drying and curing of organic solvent based layers is usually accomplished at a temperature of about 60° C. for about 20 minutes. Thorough drying and curing of water or aqueous solvent based layers is usually accomplished at a temperature of about 60° C. for about 20 minutes or at room temperature overnight. It is within the skill of the art to select suitable drying conditions.

[0185] In an embodiment, step (d) includes spraying multiple layers, for example 2, 3, 4 or 5 layers.

[0186] In an embodiment, step (d) includes n subsequent spraying steps resulting in n layers, where an xth layer is applied at least partially over an x-1th layer, where x is an integer between 2 and n, and where n is an integer between 2 and 5.

[0187] In a preferred embodiment, the retroreflective ink, coating or paint composition is applied to the substrate 1m in step (d). 2 The amount is preferably 200 to 800 g per m 2 It is applied in an amount of 300 to 600 g per area.

[0188] In an embodiment, step (b) is not performed. In a highly preferred embodiment, step (c) is not performed.

[0189] The geometry of the substrate to be coated is not limited in any way, so long as it can be coated by spraying, i.e., droplets of the retroreflective ink, coating, or paint composition can reach the surface of the substrate. In an embodiment, the substrate is flat. In another embodiment, the substrate is curved. In a further embodiment, the substrate includes flat and curved portions.

[0190] The inventors have determined that retroreflective ink, coating or paint compositions can be applied, for example, using industrial high speed spraying to a variety of substrates to result in retroreflective coating layers having excellent print or coating qualities, such as uniformity and retroreflectivity at wide angles. These results can also be obtained when the retroreflective ink, coating or paint composition is applied to the surface of a vertically positioned substrate, and even when the substrate surface is sprayed from below.

[0191] When the retroreflective coating layer is provided with one or more further transparent coating layers (i.e., step (f) of the method for coating a substrate defined above is performed), a retroreflective layer with high smoothness and improved cleanability is obtained.

[0192] In a preferred embodiment, the substrate is selected from fabric, leather, metal, concrete, rubber, plastic, carbon fiber, and combinations thereof. Fabric as used herein includes woven or knitted textile fabrics such as cotton, polyester, nylon, silk, wool, viscose, and acrylic.

[0193] Regardless of the type of material from which the substrate is made, the substrate may be selected from the group consisting of apparel, traffic signs, automobile chassis or bodies, bicycle frames, roads, pavements, and guardrails.

[0194] The substrate on which the retroreflective coating according to the present invention is applied may be provided with one or more additional transparent coating layers in step (f). These one or more additional transparent coating layers may serve to protect the retroreflective layer against abrasion and / or moisture. Furthermore, they may be used to provide the substrate coated with the retroreflective layer with a particular matte or shiny / glossy appearance. The one or more additional transparent coating layers may be colored. The one or more additional transparent coating layers applied in the optional step (f) may include a liquid coating layer, a powder coating layer, or a combination thereof, which is subsequently cured or dried.

[0195] If one or more further transparent coating layers are applied in step (f) to the layer of organic solvent-based retroreflective ink, coating or paint composition, this layer of retroreflective ink, coating or paint composition is usually not fully cured. If one or more further transparent coating layers are applied in step (f) to the layer of water or aqueous solvent-based retroreflective ink, coating or paint composition, this layer of retroreflective ink, coating or paint composition is usually fully cured. It is within the skill of the art to select suitable drying conditions.

[0196] The spraying in step (c) is preferably accomplished using curtain coating, a spray gun, a high speed rotary bell, a high speed rotating disk, or using a spray can containing a propellant. In a preferred embodiment, the spraying is accomplished without the use of a propellant.

[0197] In a third aspect, the present invention relates to a substrate coated with a retroreflective layer obtainable by the method defined above. The substrate coated with the retroreflective layer can have a matt or shiny appearance.

[0198] In a preferred embodiment, a substrate coated with a retroreflective layer, preferably coated with one or more further transparent coating layers (i.e. step (e) of the method of coating a substrate defined above is performed) exhibits retroreflection of the retroreflective layer at any angle between 0 and 80°, for example between 0 and 78°, between 0 and 75°, between 0 and 70°, between 0 and 65°, between 0 and 60°, between 0 and 55°, between 0 and 50°, between 0 and 45° and between 0 and 40° from the normal of the coated substrate. This retroreflection of the retroreflective layer is determined by directing a beam of a torch at the retroreflective layer, with the line of sight of the eye substantially coinciding with the beam of the torch, and visually determining whether retroreflection is observed. The experiment starts at an angle of 0 from the normal of the coated substrate, after which the angle is gradually increased until retroreflection is no longer discernible.

[0199] Thus, the invention has been described with reference to certain specific embodiments discussed above, it being recognized that these embodiments are susceptible to various modifications and alternative forms known to those skilled in the art.

[0200] Moreover, for the proper understanding of this specification and its claims, it should be understood that the verb "comprise" and its conjugations are used in an open-ended sense to mean that the items following the word are included, but items not specifically mentioned are not excluded. Furthermore, the reference of an element with the indefinite article "a" or "an" does not exclude the possibility that there are more than one of that element, unless the context clearly dictates that there is only one of that element. Thus, the indefinite article "a" or "an" generally means "at least one." EXAMPLES

[0201] Example 1 Six compositions according to the invention (Samples 1-5 and 7), and two comparative compositions (Samples 6 and 8) were prepared on a kg scale using the following ingredients:

[0202] Spherical glass beads: Micro glass beads (RI 2.2), having a refractive index of about 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 particle size of about 4.5 g / cm 3 The spherical glass beads were obtained from Jianxi Sunflex Light Retroreflective Material Co, Ltd. and had a specific gravity of 1.0 to 1.0 μm. These spherical glass beads contain TiO2, BaO, CaO, SiO2, and ZnO.

[0203] Micro glass beads (RI 1.9, HAC) obtained from Jianxi Sunflex Light Retroreflective Material Co, Ltd., had a refractive index of about 1.9 measured at a wavelength λ of 589 nm, a median particle size D50 of 38.22 μm, a D10 diameter of 34.86 μm, and a D90 diameter of 43.04 μm, as measured using laser diffraction, and a g / cm 3 Hemispherical aluminum coated glass beads having a specific gravity of 1. These spherical glass beads contain TiO2, BaO, SiO2, CaO and Al2O3.

[0204] Glass beads C (refractive index 2.2 measured at a wavelength λ of 589 nm) were obtained from Jianxi Sunflex Light Retroreflective Material Co, Ltd. These glass beads have a median particle size D50 of 40.4 μm, a D10 diameter of 37.3 μm, and a D90 diameter of 44.1 μm, as measured using laser diffraction.

[0205] solvent Demineralized water The solvent portion of Cromax XB155 obtained from Cromax, a mixture of organic solvents containing xylene, toluene, ethylbenzene, isopentyl acetate, n-butyl acetate, isobutanol, 2,6-dimethyl-4-heptanone, 2-methoxy-1-methylethyl acetate, and 4,6-dimethyl-heptan-2-one A mixture of organic solvents, such as xylene, ethylbenzene, naphtha, 1,2,4-trimethylbenzene, mesitylene, n-propylbenzene, isopentyl acetate, n-butyl acetate, 2-methylbutyl acetate, and 4-methyl-2-pentanone, obtained from Cromax XB383 Solvent portion of Syrox S900 (binder) obtained from Axalta Coating Systems Solvent portion of Syrox S941 (thinner) obtained from Axalta Coating Systems

[0206] Further ingredients AMP Ultra PC 2000, obtained from Angus Chemical Company; neutralizer Acticide MBL, derived from Thor; preservative Aquabase Nexa P990-8999, a water-based binder obtained from PPG Industries, Inc. Binder part of Chromax XB155 The solid portion of Syrox S900 (binder), obtained from Axalta Coating Systems Solid portion of Syrox S941 (thinner), obtained from Axalta Coating Systems

[0207] Thickener Efka RM1900, obtained from BASF, modified hydrogenated castor oil, thickener Claytone 40, derived from Rheo, organophilic phyllosilicate, thickener ACULYN Excel, a HASE thickener obtained from DOW Chemical

[0208] Pigment particles and flakes Decomet® 1050 / 10 VP / 13974, aluminum flakes with an average diameter of about 12-15 μm and a thickness <50 nm, obtained from Schlenk Metallic Pigments GmbH. Toyal EMRS-D710, aluminum flakes with an average diameter of about 10 μm and a thickness of <200 nm obtained from TOYO ALUMIMNIUM KK. Aquamet® CP-BG / 8500 / 60, silica-coated aluminum flakes with an average diameter of about 16 μm and a thickness of <1 μm, obtained from Schlenk Metallic Pigments GmbH. Xylarlic® T61-10 WNT Micro Silver, coated aluminum oxide flakes obtained from Merck KGaA, with an average diameter between 8 and 14 μm and a thickness of <1 μm. Metallic Powder – PO6690 Silver, aluminium flakes with an average diameter between 12 and 16 μm, obtained from Deco Colors Holland BV. Iriodin® 9602 Silver-Grey SW (flakes) were obtained from Merck Performance Materials Germany GmbH. These flakes are coated mica flakes with an average diameter (D50, laser diffraction) of 22.3 μm, a thickness of less than 1 μm and an aspect ratio (flake diameter / thickness) of at least 10. Iriodin® 9612 Silver-Grey Fine Satin SW (flakes) were obtained from Merck Performance Materials Germany GmbH. These flakes are coated mica flakes with an average diameter (D50, laser diffraction) of 7.2 μm, a thickness of less than 1 μm and an aspect ratio (flake diameter / thickness) of at least 10.

[0209] Three organic solvent based compositions according to the invention (Samples 1-3) were prepared by adding the ingredients to a container in the following order: (1) adding an organic solvent Chromax XB383 at room temperature (about 20° C.); (2) adding glass beads while mixing at room temperature (about 20° C.); (3) adding Claytone 40 while mixing at 1400 rpm and continuing mixing at 1400 rpm for 10 minutes at room temperature (about 20° C.); (4) adding Efka RM1900 while mixing at 1800 rpm, beginning heating to 60° C. and continuing mixing at 1800 rpm for 15 minutes; (5) continuing mixing at 1800 rpm and 60° C. for 15 minutes; (6) cooling the mixture obtained in step (5) to room temperature (about 20 to 25° C.); and (7) Add Chromax XB155 and pigment flakes while mixing at 1800 rpm and continue mixing at 1800 rpm for 10 minutes.

[0210] Three compositions according to the invention (Samples 4, 5 and 7) and two comparative compositions (Samples 6 and 8) based on water as the solvent were prepared by adding the ingredients to a vessel at room temperature (about 20° C.) in the following order: (1) adding demineralized water; (2) adding Acticide MBL while mixing at 600 rpm and continuing mixing at 600 rpm for 10 minutes; (3) adding glass beads while mixing at 800 rpm and continuing mixing at 800 rpm for 5 minutes; (4) adding AMP Ultra PC 2000 while mixing at 800 rpm and continuing mixing at 800 rpm for 10 minutes to establish a pH of about 10.5; (5) adding Accurin Excel while mixing at 2400 rpm and continuing mixing at 2400 rpm for 10 minutes; and (6) Adding Aquabase Nexa P990-8999, pigment flakes and demineralized water while mixing at 1800 rpm and continuing mixing at 1800 rpm for 10 minutes.

[0211] The amounts of the different ingredients are listed in Table 1.

[0212] [Table 1] JPEG2024521245000005.jpg225149

[0213] Example 2 The stability of six retroreflective ink, coating or paint compositions according to the invention, and two comparative compositions described in Example 1, was determined by visual and tactile inspection to see if the samples showed settling, syneresis or separation (phase or otherwise) after a certain number of days. See Table 2. A sample is considered stable if no settling, syneresis or separation can be observed upon visual and tactile inspection. A sample is considered spray stable if it can be sprayed without remixing.

[0214] [Table 2]

[0215] Example 3 Six retroreflective ink, coating or paint compositions according to the present invention, and two comparative compositions described in Example 1, were sprayed onto a flat greyish metal test plate (10.5 x 14.9 cm, 154.2 cm) with a vertical black bar (0.3 cm wide) using a spray gun (DeVILBISS HVLP, DV1-C1 Plus) equipped with a 1.3 mm nozzle. 2 The coating was applied to the entire surface of a substrate (having an effective surface area of ​​100 nm) at room temperature (approximately 20° C.).

[0216] Two types of layers were applied; "normal layer" and "mist layer". For the "normal layer", the spray gun was positioned 30 cm away from the metal test plate and a pressure of 1.8 bar was applied. For the "mist layer", the spray gun was positioned 50 cm away from the metal test plate and a pressure of 1.3 bar was applied. Good results were obtained when spraying the test plate horizontally from top to bottom or vertically.

[0217] Subsequent layers were applied "wet-on-wet", meaning that the subsequent layer was applied over the previous layer after at least some to virtually all of the solvent had evaporated, but without (complete) curing. This means that a drying time was applied between the application of subsequent layers. Intermediate drying of organic solvent-based layers was performed at a temperature between 50 and 60° C. for about 10 minutes. Intermediate drying of water or aqueous solvent-based layers was performed at a temperature between 50 and 60° C. for about 10 minutes.

[0218] As a reference the weight of the untreated metal plate was taken. After application of the individual layers and after intermediate drying the weight of the treated metal plate was measured. From these data it was possible to determine the amount of pigment flakes [g / m 2If virtually all of the solvent is evaporated during the drying step, the amount of composition applied to the metal plate [g / m 2 ] can be calculated. In Example 3.1, one normal layer was applied. In Example 3.2, one normal layer and one mist layer were applied. In Example 3.3, two normal layers and one mist layer were applied. Finally, in Example 3.4, three normal layers and one mist layer were applied.

[0219] The overall (off-center) retroreflectivity and coverage of the coated substrates were visually inspected and evaluated after complete drying and curing (i.e., after 20 minutes at 60° C.). Additionally, the maximum angle of retroreflection [°] was determined by directing the beam of a torch at the retroreflective layer such that the line of sight of the eye is substantially coincident with the beam of the torch, and visually determining whether retroreflection is observed or not. The experiment started at an angle of 0, normal to the coated substrate, and then the angle was gradually increased until retroreflection was no longer discernible.

[0220] Qualification "----" means very poor, and qualification "++++" means very good. Very good coverage means that the surface has a homogenous color and when tested for retroreflectivity, the vertical black bars of the test plate are not visible under normal lighting conditions nor under the application of a light torch. A score of "+" is considered unsatisfactory. Details are presented in Table 3.

[0221] [Table 3] JPEG2024521245000008.jpg225149 JPEG2024521245000009.jpg225149

[0222] From Table 3, Example 3.1, it can be concluded that the application of a single normal layer of a composition according to the invention is usually not sufficient. Only sample 4 according to the invention gave sufficient results. As expected, the coverage of the comparative compositions with a high concentration of pigment flakes (samples 6 and 8) is sufficient. However, the retroreflectivity of samples 6 and 8 is clearly insufficient. As a result, the angle of retroreflection of sample 6 cannot even be determined.

[0223] Also, from Table 3, Examples 3.2 to 3.4, the application of further layers results in a higher amount of pigment flakes [g / m 2 It can be concluded that the application of [] improves the coverage but also unexpectedly improves the retroreflectivity of the compositions according to the invention (Samples 1-5 and 7). However, the retroreflectivity of Samples 6 and 8 remains clearly insufficient even after the application of the further layer.

[0224] Furthermore, from Table 3, it can be seen that the composition according to the invention can be used to obtain a sufficiently large amount [g / m 2 ] of pigment flakes having the dimensions defined above. 2 It can be concluded that by choosing a suitable amount of layers or layer thicknesses that result in a good coverage and retroreflectivity, it is always possible to obtain layers with good or even very good coverage and retroreflectivity. This unique combination of good coverage and retroreflectivity cannot be obtained using comparative compositions (samples 6 and 8) that contain high concentrations of pigment flakes with the dimensions defined above. Furthermore, it has been found that the synthetic pigment flakes and spherical glass beads contribute synergistically to coverage.

[0225] Example 4 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 a temperature of about 25° C., and using a Brookfield Viscometer with a #3 spindle rotating at 0.5 and 20 rpm at a temperature of about 25° C. The results are shown in Tables 5 and 6. As shown in Table 6, the retroreflective ink, coating or paint compositions according to the invention and the comparative compositions exhibit shear thinning behavior.

[0226] [Table 4]

[0227] [Table 5]

[0228] Example 5 Two compositions (Sample 9 and Sample 10) were prepared that differed only in the size of the synthetic pigment flakes. The compositions (weight percent) are as shown in Table 7 (the liquid portions of the ingredients are collected under "Solvent" and the weight percent of the remaining ingredients along with their solid fractions are given).

[0229] [Table 6]

[0230] Both compositions contain the same concentration and type of synthetic pigment flakes. The only difference between the two compositions is the diameter of the synthetic pigment flakes. The ratio (%) of the average synthetic pigment flake diameter to the median diameter of the spherical glass beads in sample 9 is 56%, while this ratio is 18% in sample 10.

[0231] Both compositions were applied over the surface of a flat greyish metal test plate (10.5 x 14.9 cm) with a vertical black bar (0.3 cm wide) at room temperature (approximately 20°C) using a spray gun (DV1.2 Mini) with a 1.2 mm nozzle. Two types of layers were applied; a "normal layer" and a "mist layer". For the "normal layer", the spray gun was positioned 30-40 cm away from the metal test plate and a pressure of 2.0 bar was applied. For the "mist layer", the spray gun was positioned 40-50 cm away from the metal test plate and a pressure of 1.5 bar was applied. The mist layer is a very thin layer of droplets (i.e. not a complete layer) that is applied first to improve adhesion.

[0232] Drying was provided between applications of subsequent "normal layers." Both compositions were applied to a greyish metal test plate as a mist layer, followed by drying with a subsequent normal layer on top of the mist layer, followed by drying and application of a clear topcoat, followed by drying again ["single layer," coatings (b) and (d)]. Both compositions were applied to a further greyish metal test plate as a mist layer, with two subsequent normal layers, including intermediate and final drying, and also application of a clear topcoat, followed by drying again ["multilayer," coatings (a) and (c)].

[0233] The coated substrates were visually inspected for gross (off-center) retroreflectivity and coverage. Coverage of the coated layer was assessed by checking whether the surface had a uniform color and whether the vertical black bar on the test plate was not visible under normal lighting conditions (sunlight) and under the application of a torch light ("flash") used to test retroreflectivity.

[0234] FIG. 1 shows the coverage of the coated layers under normal illumination conditions. It is clear that the larger synthetic pigment flakes provide much better coverage, especially when multiple layers are applied. In coating (a), the vertical black bars are hardly noticeable anymore. FIG. 2 shows the coverage and retroreflectivity under application of torch light ("flash"). It is again clear that the larger synthetic pigment flakes provide much better coverage, especially when multiple layers are applied. In coating (a), the vertical black bars are hardly noticeable anymore even under application of torch light. Moreover, the retroreflectivity is unexpectedly much better for the larger synthetic pigment flakes. Thus, the larger ratio of synthetic pigment flake diameter to spherical glass bead diameter unexpectedly results in a combination of good coverage and improved retroreflectivity.

Claims

1. A retroreflective ink, coating or paint composition comprising, based on the total weight of the composition: 15-75% by weight of a solvent; 1-80% by weight of spherical glass beads having a median particle size D50 between 1 and 150 μm as measured by laser diffraction and a refractive index between 1.5 and 2.8 as measured at a wavelength λ of 589 nm; 0.05 to 2.5% by weight of one or more thickening agents; and 0.20-4.5% by weight of synthetic pigment flakes having an average diameter between 1 and 75 μm, a thickness of less than 1 μm and an aspect ratio (flake diameter / thickness) of at least 10, said synthetic pigment flakes being selected from (A), (B), (C) or combinations thereof; 0-2% by weight of one or more pigment flakes or particles (D) other than the synthetic pigment flakes (A), (B) and (C); 0-30% by weight of one or more further components, (A) optionally a metal oxide, a metal, a metal sulfide, a titanium suboxide, a titanium oxynitride, FeO(OH), SiO ２ , B ２ O ３ , GeO ２ , MgF ２ , metal flakes or synthetic mica flakes coated with at least one layer of one or more components selected from the group consisting of metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (B) Metal oxides, metals, metal sulfides, titanium suboxide, titanium oxynitride, FeO(OH), SiO ２ , B ２ O ３ , GeO ２ , alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders. ２ O ３ , SiO ２ , glass, ceramic, graphite or mica platelets; (C) Metal oxides, metals, metal sulfides, titanium suboxide, titanium oxynitride, FeO(OH), SiO ２ , B ２ O ３ , GeO ２ , alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders. ２ , ZrO ２ , SiO ２ , SnO ２ , In ２ O ３ Al doped with one or more components selected from the group consisting of ZnO and iron oxide. ２ O ３ Flakes containing platelets; A retroreflective ink, coating or paint composition 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 and 4.5% by weight, and the average diameter of said synthetic pigment flakes is greater than 30% of the median particle size D50 of said spherical glass beads.

2. Based on the total weight of the composition, 15-68 wt. % solvent; 10-50% by weight of spherical glass beads having a median particle size D50 between 5 and 150 μm as measured by laser diffraction and a refractive index between 1.5 and 2.8 as measured at a wavelength λ of 589 nm; 0.05 to 2.5% by weight of one or more thickening agents; and 0.20-4.5% by weight of synthetic pigment flakes having an average diameter between 5 and 50 μm, a thickness of less than 1 μm and an aspect ratio (flake diameter / thickness) of at least 10, said synthetic pigment flakes being selected from (A), (B), (C) or combinations thereof; 0-2% by weight of one or more pigment flakes or particles (D) other than the synthetic pigment flakes (A), (B) and (C); 0-30% by weight of one or more further components, (A) optionally a metal oxide, a metal, a metal sulfide, a titanium suboxide, a titanium oxynitride, FeO(OH), SiO ２ , B ２ O ３ , GeO ２ , MgF ２ , metal flakes or synthetic mica flakes coated with at least one layer of one or more components selected from the group consisting of metal alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders; (B) Metal oxides, metals, metal sulfides, titanium suboxide, titanium oxynitride, FeO(OH), SiO ２ , B ２ O ３ , GeO ２ , alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders. ２ O ３ , SiO ２ , glass, ceramic, graphite or mica platelets; (C) Metal oxides, metals, metal sulfides, titanium suboxide, titanium oxynitride, FeO(OH), SiO ２ , B ２ O ３ , GeO ２ , alloys, rare earth compounds, and optionally coated with an outer layer comprising one or more colorants and binders. ２ , ZrO ２ , SiO ２ , SnO ２ , In ２ O ３ Al doped with one or more components selected from the group consisting of ZnO and iron oxide. ２ O ３ Flakes containing platelets, 10. The retroreflective ink, coating or paint composition of claim 1 , wherein the combined amount of the synthetic pigment flakes (A), (B) and (C) and the one or more pigment flakes or particles (D) is between 0.20 and 4.5% by weight.

3. 10. The retroreflective ink, coating or paint composition of claim 1, wherein the average diameter of the synthetic pigment flakes is greater than 33%, e.g., 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% of the median particle size D50 of the spherical glass beads.

4. The spherical glass beads are (i) between 2.0 and 2.8, preferably between 2.1 and 2.4; or 2. The retroreflective ink, coating or paint composition of claim 1, having (ii) a refractive index measured at a wavelength λ of 589 nm of between 1.7 and 2.1, preferably between 1.8 and 2.

0.

5. The retroreflective ink, coating or paint composition of claim 1 , wherein said spherical glass beads are hemispherically coated with an aluminum coating.

6. SiO ２ Aluminum flakes or SiO ２ 10. The retroreflective ink, coating or paint composition of claim 1 comprising synthetic pigment flakes (A) which are aluminum flakes coated with a layer and coated with an outer layer comprising one or more colorants and a binder.

7. TiO ２ Al coated with ２ O ３ thin section, Fe ２ O ３ Al coated with ２ O ３ thin section, TiO ２ and Fe ２ O ３ Al coated with a mixture of ２ O ３ 10. The retroreflective ink, coating or paint composition of claim 1 comprising synthetic pigment flakes (B) selected from the group consisting of flakes and combinations thereof.

8. 10. The retroreflective ink, coating or paint composition of claim 1 comprising synthetic pigment flakes (A) that are uncoated aluminum flakes or uncoated synthetic mica flakes.

9. 2. The retroreflective ink, coating or paint composition of claim 1, wherein the solvent is water or an aqueous solvent and the one or more thickeners are selected from the group consisting of ASE polymers, HASE polymers, HEUR polymers, liquid acrylic crosslinked or copolymer dispersions, acrylate crosspolymers, crosslinked polyacrylic acid polymers, crosslinked polyacrylic acid copolymers, non-ionic aqueous emulsions of modified ethylene vinyl acetate copolymer waxes, modified ureas or urea modified polyamides, and combinations thereof.

10. 2. The retroreflective ink, coating or paint composition of claim 1, wherein the solvent is an organic solvent and the one or more thickeners are selected from the group consisting of (modified) hydrogenated castor oil, clays, modified clays, calcium sulfonate complexes, organophilic phyllosilicates, silica gels, synthetic amorphous silicas, acrylic acid type gelling agents, modified cellulosic materials, polyurea dispersions, solutions of urea modified polyamides, polyurethane dispersions and combinations thereof.

11. A retroreflective ink, coating or paint composition according to claim 10, in which two thickeners are applied, preferably a modified hydrogenated castor oil and an organophilic phyllosilicate.

12. 2. The retroreflective ink, coating or paint composition of claim 1 comprising a combined amount of synthetic pigment flakes (A), (B) and (C) of 0.20 to 4.0 wt%, preferably 0.20 to 3.5 wt%, more preferably 0.20 to 3.0 wt%, even more preferably 0.20 to 2.5 wt%, and still more preferably 0.20 to 2.0 wt%.

13. The retroreflective ink, coating or paint composition of claim 1 , wherein the one or more additional components are selected from the group consisting of binders and resins, preservatives, dyes and curing initiators.

14. 1. A method of coating a substrate with a retroreflective layer, comprising: a) providing a substrate; b) optionally applying a primer layer to the substrate of step (a); c) optionally, but not preferably, applying a colored base layer to said substrate in step (a) or to said primer layer in step (b); d) applying from 0.25 to 30 g / m of a retroreflective ink, coating or paint composition according to any one of claims 1 to 13 onto the substrate of step (a) or the layer of step (b) or (c). ２ in an amount to provide a total amount of said synthetic pigment flakes (A), (B) and (C) and said one or more pigment flakes or particles (D); e) drying and curing the substrate coated with the retroreflective layer obtained in step (d); and f) optionally coating the dry substrate coated with the retroreflective layer obtained in step (e) with one or more further transparent coating layers, followed by drying or curing.

15. 15. The method of claim 14, wherein the retroreflective ink, coating or paint composition is sprayed onto the substrate in step (d) using curtain coating, a spray gun, a high speed rotary bell, a high speed rotating disk, or using a spray can containing a propellant.

16. 15. The method of claim 14, wherein step (d) comprises n subsequent spraying steps resulting in n layers, where an xth layer is applied at least partially over an x-1th layer, where x is an integer between 2 and n, and n is an integer between 2 and 5.

17. A substrate coated with a retroreflective layer obtainable by the method of claim 14.

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