Patent Description:
Autonomous vehicles can use various sensor systems such as, cameras, radar, and LIDAR (Light Imaging, Detection, and Ranging), to detect and locate obstacles in order to safely navigate through an environment. Typically, a LIDAR system includes a NIR source to emit NIR electromagnetic radiation and a NIR detector to detect NIR electromagnetic radiation reflected by the obstacle. A NIR electromagnetic radiation source can comprise, for example, a light emitting diode, a laser diode, or any light source that can be capable of emitting NIR electromagnetic radiation. A NIR detector may be a semiconductor detector that can be capable of sensing NIR electromagnetic radiation, such as, a photodiode, a silicon-based charged-coupled device, an indium gallium arsenide detector, a lead sulfide detector, and a lead selenide detector. Some obstacles may present detection challenges for some LIDAR systems.

<CIT> relates to compositions including surface-modified nanoparticles, articles, and methods of making same. <CIT> related to articles with cleanable surfaces, methods for making them, and methods for using them. <CIT> relates to dew resistant coatings and articles having the dew resistant coating adhered thereto. <CIT> relates to methods and systems for generating light emission or reflectance from visible displays and colored surfaces. <CIT> relates to basic film forming coating compositions including inorganic oxide nanoparticles and an organic base, as well as methods and coated substrates. <CIT> relates to face of a road or information signs and the use of a UV-curable varnish for the production of the face of a road or information signs.

The present disclosure provides a coating composition for application over a retroreflective substrate. The coating comprises a resin and a pigment. The pigment is suitable to absorb and/or scatter electromagnetic radiation in a wavelength range of <NUM> to <NUM>. The pigment comprises zinc oxide, alumina, antimony tin oxide, tungsten oxide, gold nanoparticles, silver nanoparticles, copper nanoparticles, lanthanum hexaboride, dicopper hydroxide phosphate, a phthalocyanine, or a combination thereof. A coating formed from the coating composition comprises a ratio of reduction in electromagnetic radiation retroreflectance at a wavelength of <NUM> and/or <NUM> to reduction in electromagnetic radiation retroreflectance averaged over a wavelength range of <NUM> to <NUM> of at least <NUM>:<NUM>. The coating absorbs at least <NUM> absorbance units of electromagnetic radiation at a wavelength of <NUM>, and/or the coating absorbs at least <NUM> absorbance units of electromagnetic radiation at a wavelength of <NUM>.

The present disclosure also provides a method for producing a retroreflective article with reduced electromagnetic radiation retroreflection at a wavelength of <NUM> and/or <NUM>. A coating composition is deposited over a retroreflective substrate to form a coating. The coating composition comprises a resin and a pigment. The pigment is suitable to absorb and/or scatter electromagnetic radiation in a wavelength range of <NUM> to <NUM>. The pigment comprises zinc oxide, alumina, antimony tin oxide, tungsten oxide, gold nanoparticles, silver nanoparticles, copper nanoparticles, lanthanum hexaboride, dicopper hydroxide phosphate, a phthalocyanine, or a combination thereof. The coating comprises a ratio of reduction in electromagnetic radiation retroreflectance at a wavelength of <NUM> and/or <NUM> to reduction in electromagnetic radiation retroreflectance averaged over a wavelength range of <NUM> to <NUM> of at least <NUM>:<NUM>. The coating absorbs at least <NUM> absorbance units of electromagnetic radiation at a wavelength of <NUM>, and/or the coating absorbs at least <NUM> absorbance units of electromagnetic radiation at a wavelength of <NUM>.

The present disclosure also provides a retroreflective article. The article comprises a retroreflective substrate and a coating disposed over the retroreflective substrate. The coating comprises a resin and a pigment. The pigment is suitable to absorb and/or scatter electromagnetic radiation in a wavelength range of <NUM> to <NUM>. The pigment comprises zinc oxide, alumina, antimony tin oxide, tungsten oxide, gold nanoparticles, silver nanoparticles, copper nanoparticles, lanthanum hexaboride, dicopper hydroxide phosphate, a phthalocyanine, or a combination thereof. The coating comprises a ratio of reduction in electromagnetic radiation retroreflectance at a wavelength of <NUM> and/or <NUM> to reduction in electromagnetic radiation retroreflectance averaged over a wavelength range of <NUM> to <NUM> of at least <NUM>:<NUM>. The coating absorbs at least <NUM> absorbance units of electromagnetic radiation at a wavelength of <NUM>, and/or the coating absorbs at least <NUM> absorbance units of electromagnetic radiation at a wavelength of <NUM>.

It is understood that the inventions described in this specification are not limited to the examples summarized in this Summary. Various other aspects are described and exemplified herein.

The features and advantages of the examples, and the manner of attaining them, will become more apparent, and the examples will be better understood by reference to the following description of examples taken in conjunction with the accompanying drawings, wherein:.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate certain examples, in one form, and such exemplifications are not to be construed as limiting the scope of the examples in any manner.

Certain exemplary examples of the present disclosure will now be described to provide an overall understanding of the principles of the composition, function, manufacture, and use of the compositions and methods disclosed herein. One or more examples are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the compositions, articles, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary examples and that the scope of the various examples of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary example may be combined with the features of other examples. Such modifications and variations are intended to be included within the scope of the present invention.

Reference throughout the specification to "various examples," "some examples," "one example," "an example," or the like, means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example. Thus, appearances of the phrases "in various examples," "in some examples," "in one example," "in an example," or the like, in places throughout the specification are not necessarily all referring to the same example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more examples. Thus, the particular features, structures, or characteristics illustrated or described in connection with one example may be combined, in whole or in part, with the features, structures, or characteristics of one or more other examples without limitation. Such modifications and variations are intended to be included within the scope of the present examples.

As used in this specification, particularly in connection with coating layers or films, the terms "on," "onto," "over," and variants thereof (e.g., "applied over," "formed over," "deposited over," "provided over," "located over," and the like) mean applied, formed, deposited, provided, or otherwise located over a surface of a substrate but not necessarily in contact with the surface of the substrate. For example, a coating layer "applied over" a substrate does not preclude the presence of one or more other coating layers of the same or different composition located between the applied coating layer and the substrate. Likewise, a second coating layer "applied over" a first coating layer does not preclude the presence of one or more other coating layers of the same or different composition located between the applied second coating layer and the applied first coating layer.

As used in this specification, the terms "polymer" and "polymeric" means prepolymers, oligomers, and both homopolymers and copolymers. As used in this specification, "prepolymer" means a polymer precursor capable of further reactions or polymerization by one or more reactive groups to form a higher molecular mass or cross-linked state.

As used in this specification, the terms "cure" and "curing" refer to the chemical crosslinking of components in a coating composition applied as a coating layer over a substrate. Accordingly, the terms "cure" and "curing" do not encompass solely physical drying of coating compositions through solvent or carrier evaporation. In this regard, the term "cured," as used in this specification, refers to the condition of a coating layer in which a component of the coating composition forming the layer has chemically reacted to form new covalent bonds in the coating layer (e.g., new covalent bonds formed between a binder resin and a curing agent).

As used in this specification, the term "formed" refers to the creation of an object from a composition by a suitable process, such as, curing. For example, a coating formed from a curable coating composition refers to the creation of a single or multiple layered coating or coated article from the curable coating composition by curing the coating composition under suitable process conditions.

Retroreflective substrates have been used on various articles, such as, for example, a tape, a sign, a vehicle, a marker, and clothing, in order to increase their visibility upon illumination at night. The increased visibility can enhance the ability of a driver to see the sign, including the retroreflective substrate (e.g., a stop sign, a yield sign, a one-way sign), or a person wearing clothing, including the retroreflective substrate. The increased visibility can enable the driver to safely observe the article and navigate around the article or person.

A retroreflective substrate operates by receiving electromagnetic radiation from an electromagnetic radiation source and reflecting the received electromagnetic radiation back to the electromagnetic source in the anti-parallel direction it was received. For example, electromagnetic radiation received by a retroreflective substrate traveling in a source vector can be reflected back along a return vector substantially parallel to the source vector but in the opposite direction of the source vector.

As used herein, the term "retroreflectance" means the ability of an article to reflect electromagnetic radiation in a return vector that is substantially parallel but opposite in direction to a source vector and/or the ability of a coating to permit the reflectance of electromagnetic radiation by the article in a return vector that is substantially parallel but opposite in direction to a source vector. As used herein, the term "reflectance" means the returning or throwing back of electromagnetic radiation by a surface upon which the electromagnetic radiation is incident. As used herein, the term "extinction" means the absorbing and/or scattering of electromagnetic radiation.

As used herein, the terms "near infrared range" or "NIR" refer to the near infrared range of the electromagnetic spectrum. For example, the NIR range may have a wavelength range of <NUM> to <NUM>, such as, <NUM> to <NUM>. The NIR range may include a wavelength of <NUM> and/or <NUM>. As used herein, the term "visible" refers to the visible range of the electromagnetic spectrum. For example, the visible range may be a wavelength range of <NUM> to <NUM>.

As used herein, the term "NIR retroreflectance" means the ability of an article to retroreflect electromagnetic radiation in the NIR range of the electromagnetic spectrum and/or the ability of a coating to permit the retroreflectance of the article in the NIR range of the electromagnetic spectrum. As used herein, the term "visible retroreflectance" means the ability of an article to retroreflect electromagnetic radiation in the visible range of the electromagnetic spectrum and/or the ability of a coating to permit the retroreflectance of the article in the visible range of the electromagnetic spectrum. As used herein, the term "NIR extinction" means the ability of a coating to absorb and/or scatter electromagnetic radiation in the NIR range of the electromagnetic spectrum. As used herein, the term "visible extinction" means the ability of a coating to absorb and/or scatter electromagnetic radiation in the visible range of the electromagnetic spectrum.

It can be a challenge for LIDAR systems to properly detect the size and position of a retroreflective substrate because the retroreflective substrate may reflect more NIR electromagnetic radiation back to the LIDAR system than a similarly positioned and sized non-retroreflective substrate. The increased reflectance can result in system saturation that may lead to an improper calculation by the LIDAR system. As a result, the article that employs the retroreflective substrate may appear to the LIDAR system to be larger than a similarly positioned and sized non-retroreflective substrate. The improper calculation can lead to inaccurate mapping of an environment by the LIDAR system and, thus, inaccurate navigation by an autonomous vehicle employing the LIDAR system.

Provided herein are retroreflective substrates, coatings for application over a retroreflective substrate, retroreflective articles comprising the coating, and methods of production thereof. The coatings of the present disclosure can reduce the NIR retroreflectance of the retroreflective substrate and/or the NIR extinction of the coating while maintaining a sufficient level of visible retroreflectance and/or visible extinction of the coating. The coatings can also enable autonomous vehicles to more accurately detect and calculate the size and/or position of the retroreflective substrate while still providing sufficient visible retroreflectance and/or extinction of the coating and minimizing a visible color change in the underlying substrate.

As illustrated in <FIG>, a retroreflective article <NUM> comprising a retroreflective substrate <NUM> and a coating <NUM> disposed on the retroreflective substrate <NUM> is provided. The coating <NUM> can be suitable to scatter and/or absorb electromagnetic radiation in the NIR range. The coating <NUM> can reduce NIR retroreflectance of the retroreflective substrate <NUM>. The article can be, for example, at least one of a tape, a sign, a vehicle, a marker, clothing, and any obstacle that may be located in a path of a moving vehicle. A marker can comprise at least one of a barrier, a barricade, a speed bump, a traffic cone, a road surface, and the like. A vehicle can comprise any type of moving vehicle, such as, at least one of an automobile, a bicycle, a truck, a bus, an airplane, a boat, a drone, a submarine, and the like.

The retroreflective substrate <NUM> can comprise, for example, metal, plastic, ceramic, fabric, wood, cement, asphalt, glass, stone, and combinations thereof. The metal can comprise tin, tin alloy, aluminum, aluminum alloy, iron, and iron alloy, and combinations thereof. The plastic can comprise a polymeric material, such as, polyester, polyolefin, polyamide, cellulosic, polystyrene, polyacrylic, poly(ethylene naphthalate), polypropylene, polyethylene, nylon, ethylene vinyl alcohol, polylactic acid, poly(ethyleneterephthalate), polycarbonate, polycarbonate acrylobutadiene styrene, polyamide, and combinations thereof.

The retroreflective substrate <NUM> is at least partially coated with a coating composition of the present disclosure to form coating <NUM>. Coating compositions of the present disclosure can be formulated as a solvent-based composition, a water-based composition, or a <NUM>% solid composition that does not comprise a volatile solvent or aqueous carrier. The coating compositions of the present disclosure can be a liquid at a temperature of -<NUM> or greater, such as, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, or <NUM> or greater, can be a liquid at a temperature of <NUM> or lower, such as, <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, or <NUM> or lower, and can be a liquid at a temperature in a range of -<NUM> to <NUM>, such as, -<NUM> to <NUM>, -<NUM> to <NUM>, -<NUM> to <NUM>, or <NUM> to <NUM>. For example, the coating compositions of the present disclosure can be a liquid at room temperature.

The coating compositions of the present disclosure comprise a film-forming resin. The film-forming resin can include a resin that can form a self-supporting continuous film on surface of a substrate (e.g., retroreflective substrate <NUM>) upon removal of any diluents or carriers present with the film-forming resin or upon curing at ambient or elevated temperature. A film-forming resin can comprise, for example, at least one of an automotive original equipment manufacturer coating composition, an automotive refinish coating composition, an industrial coating composition, an architectural coating composition, a coil coating composition, a packaging coating composition, a marine coating composition, and an aerospace coating composition, and the like.

The film-forming resin can comprise at least one of a thermosetting film-forming resin and a thermoplastic film-forming resin. As used herein, the term "thermosetting" refers to resins that "set" irreversibly upon curing or crosslinking, where the polymer chains of the polymeric components are joined together by covalent bonds, which is often induced, for example, by heat or radiation. Curing or a crosslinking reaction can be carried out under ambient conditions. Once cured or crosslinked, a thermosetting film-forming resin may not melt upon the application of heat and can be insoluble in conventional solvents. As used herein, the term "thermoplastic" refers to resins that include polymeric components that are not joined by covalent bonds and thereby can undergo liquid flow upon heating and are soluble in conventional solvents.

Thermosetting coating compositions may include a crosslinking agent that may be selected from, for example, aminoplasts, polyisocyanates including blocked isocyanates, polyepoxides, beta-hydroxyalkylamides, polyacids, anhydrides, organometallic acid-functional materials, polyamines, polyamides, and mixtures of any of the foregoing.

A film-forming resin may have functional groups that are reactive with the crosslinking agent. The film-forming resin in the coating compositions described herein may be selected from any of a variety of polymers well-known in the art. The film-forming resin may be selected from, for example, acrylic polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyether polymers, polysiloxane polymers, copolymers thereof, and mixtures thereof. Generally, these polymers may be any polymers of these types made by any method known to those skilled in the art. The functional groups on the film-forming resin may be selected from any of a variety of reactive functional groups, including, for example, carboxylic acid groups, amine groups, epoxide groups, hydroxyl groups, thiol groups, carbamate groups, amide groups, urea groups, isocyanate groups (including blocked isocyanate groups), mercaptan groups, and combinations thereof.

The coating compositions of the present disclosure can comprise a pigment suitable to reduce NIR transmittance and/or increase NIR extinction of the coating <NUM> formed therefrom and/or reduce NIR retroreflectance of the article <NUM>. As used herein, the term "pigment" refers to inorganic or organic particulate materials which are practically insoluble in the medium in which they are incorporated. The pigment can comprise various compounds that can absorb and/or scatter NIR electromagnetic radiation and the pigment can minimally, if at all, absorb and/or scatter visible electromagnetic radiation. The pigment can absorb NIR electromagnetic radiation and minimally, if at all, scatter NIR electromagnetic radiation. The pigment can scatter NIR electromagnetic radiation and minimally, if at all, absorb NIR electromagnetic radiation. The pigment can both scatter NIR electromagnetic radiation and absorb NIR electromagnetic radiation. The pigment comprises at least one of zinc oxide, alumina, antimony tin oxide, tungsten oxide (reduced or unreduced), gold nanoparticles, silver nanoparticles, copper nanoparticles, lanthanum hexaboride, dicopper hydroxide phosphate, and a phthalocyanine. For example, the pigment can comprise or consist essentially of lanthanum hexaboride. The nanoparticles can be spherical, rod-shaped, and/or tube-shaped. The preference of the pigment to absorb and/or scatter NIR electromagnetic radiation can enable the coating composition and coating <NUM> formed therefrom to reduce NIR transmittance while maintaining sufficient visible transmittance.

The average particle size of the pigment can affect the NIR extinction of the coating <NUM>, the visible extinction of the coating <NUM>, the NIR retroreflectance of the article <NUM>, the visible retroreflectance of the article <NUM>, and/or the observable color of the retroreflective substrate <NUM>. The average particle size of the pigment can be <NUM> or greater such as, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, or <NUM> or greater. The average particle size of the pigment can be <NUM> or lower, such as, <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, or <NUM> or lower. The average particle size of the pigment can be in a range of <NUM> to <NUM>, such as, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. Decreasing the average particle size of the pigment can increase a ratio of reduction in NIR transmittance to reduction in visible transmittance by the pigment.

As used herein, "average particle size" refers to the z-average size measured using dynamic light scattering which is the intensity-weighted harmonic mean particle diameter. Average particle size according to the present disclosure can be measured according to ASTM E2490.

In order to make the coating composition, a pigment composition comprising the pigment can be combined with the film-forming resin. The pigment composition can be formed by at least one of grinding and milling a pigment source material in order to reduce the particle size of the pigment. For example, the average particle size of the pigment can be reduced to <NUM> or lower, such as, a reduction to <NUM> or lower, a reduction to <NUM> or lower, a reduction to <NUM> or lower, a reduction to <NUM> or lower, or a reduction to <NUM> or lower. For example, the average particle size can be reduced to a range of <NUM> to <NUM>, such as, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>.

The pigment composition and film-forming resin can be mixed to homogenize the components and form the coating composition. The coating composition can be stored before use. The coating composition can be curable.

The coating compositions of the present disclosure can be formulated with a liquid viscosity suitable for atomization and droplet formation under the high shear conditions associated with single or multiple component airless spray application techniques at a temperature -<NUM> or greater such as, a temperature of <NUM> or greater, a temperature of <NUM> or greater, a temperature of <NUM> or greater, a temperature of <NUM> or greater, or a temperature of <NUM> or greater. The compositions can be formulated with a liquid viscosity suitable for atomization and droplet formation under the high shear conditions associated with single or multiple component airless spray application techniques at a temperature of <NUM> or lower such as, <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, or <NUM> or lower. Compositions of the present disclosure can be formulated with a liquid viscosity suitable for atomization and droplet formation under the high shear conditions associated with single or multiple component airless spray application techniques in a temperature range of -<NUM> to <NUM> such as, -<NUM> to <NUM>, -<NUM> to <NUM>, -<NUM> to <NUM>, or <NUM> to <NUM>.

The coating compositions of the present disclosure can be deposited over the retroreflective substrate <NUM> either in situ, after the article <NUM> is already on location, or as part of the manufacturing process of the article <NUM>. For example, compositions of the present disclosure can be applied as an application over <NUM>% or greater of an exterior surface area of the retroreflective substrate <NUM>, such as, <NUM>% or greater, <NUM>% or greater, <NUM>% or greater, <NUM>% or greater, <NUM>% or greater, or <NUM>% or greater, of an exterior surface area of the retroreflective substrate <NUM>. For example, the coating compositions can cover <NUM>% or less of an exterior surface area of the retroreflective substrate <NUM>, such as, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, or <NUM>% or less, of an exterior surface area of the retroreflective substrate <NUM>. For example, the coating compositions can cover <NUM>% to <NUM>% of an exterior surface area of the retroreflective substrate <NUM>, such as, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, or <NUM>% to <NUM>%, of an exterior surface area of the retroreflective substrate <NUM>.

By way of example, if the article <NUM> is a street sign, the coating composition of the present disclosure may be applied on-site and form a coating over an existing and already installed street sign. Where the article <NUM> is a newly manufactured street sign, the coating composition of the present disclosure may be applied as part of the manufacturing process of the street sign prior to on-site installation of the sign. Where the article <NUM> is newly manufactured clothing, the coating composition of the present disclosure may be applied as part of the manufacturing process of the clothing. The coating composition of the present disclosure may be manufactured into a preformed film and thereafter applied to the article <NUM>.

The coating composition can be deposited by at least one of spray coating, spin coating, dip coating, roll coating, flow coating, and film coating. After deposition of the coating composition to the retroreflective substrate <NUM>, the coating composition may be allowed to coalesce to form a substantially continuous film on the retroreflective substrate <NUM> and the coating composition can be cured to form the coating <NUM>. The coating composition can be cured at a temperature of -<NUM> or greater such as, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, or <NUM> or greater. The coating composition can be cured at a temperature of <NUM> or lower such as, <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, or <NUM> or lower. The coating composition can be cured at a temperature in a range of -<NUM> to <NUM> such as, -<NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. The curing can comprise a thermal bake in an oven.

The dry film thickness of the coating <NUM> can be <NUM> or greater, such as, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, or <NUM> or greater. The dry film thickness of the coating <NUM> can be <NUM> or less, such as, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, <NUM> or less, or <NUM> or less. The dry film thickness of the coating <NUM> can be in a range of <NUM> to <NUM>, such as, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. The dry film thickness of the coating <NUM> can affect the absorption and/or scattering of NIR electromagnetic radiation by the coating <NUM>.

The coating <NUM> may be a single layer or a multilayer coating system, such as a coating system including at least two coating layers, a first coating layer and a second coating layer underneath at least a portion of the first coating layer. The retroreflective article <NUM> can comprise additional layers, such as, a clear coat, a primer, and combinations thereof. Compositions of the present disclosure can be deposited directly on a surface of the retroreflective substrate <NUM> or over a primer or other underlying layer.

The coating <NUM> can be substantially clear. As used herein, the term "substantially clear" refers to a coating that has a minimal, if any, scattering or diffuse reflection of visible electromagnetic radiation. The coating <NUM> can be colorless. The coating <NUM> may include a colorant; however, in such cases, the colorant is not present in an amount sufficient to render the coating <NUM> opaque.

As stated herein, the coating <NUM> can be suitable to reduce NIR retroreflectance of the retroreflective substrate <NUM>. For example, a source <NUM> can comprise a NIR electromagnetic radiation source 114a and emit NIR electromagnetic radiation <NUM>, which can be absorbed by the coating <NUM>, can be scattered as diffuse NIR electromagnetic radiation 108b upon traversing the coating <NUM>, and/or can reach the retroreflective substrate <NUM>. The NIR electromagnetic radiation <NUM> that reaches the retroreflective substrate <NUM> can be reflected back through the coating <NUM> to the source <NUM> as returned NIR electromagnetic radiation 108a. The returned NIR electromagnetic radiation 108a can be traveling in a first vector substantially parallel to a second vector that NIR electromagnetic radiation <NUM> is traveling. The first vector can be in a direction opposite of a direction of the second vector. The diffuse NIR electromagnetic radiation 108b may not return to source <NUM>.

The source <NUM> can comprise a NIR detector 114b. The returned NIR electromagnetic radiation 108a can be sensed by NIR detector 114b. Due to the absorption and/or scattering of the NIR electromagnetic radiation <NUM> by the coating <NUM>, the returned NIR electromagnetic radiation 108a has a reduced magnitude compared to a magnitude of the NIR electromagnetic radiation <NUM>. The reduced magnitude can prevent the NIR detector 114b from becoming saturated with NIR electromagnetic radiation.

As illustrated in <FIG>, the source <NUM> can comprise a visible electromagnetic radiation source 114c and emit visible electromagnetic radiation <NUM>, which may be substantially unaffected by the coating <NUM>. The visible electromagnetic radiation <NUM> can reach the retroreflective substrate <NUM> and can be reflected back through the coating <NUM> to the source <NUM> as returned visible electromagnetic radiation <NUM>. The returned visible electromagnetic radiation <NUM> can be traveling in a third vector substantially parallel to the direction of a fourth vector that visible electromagnetic radiation <NUM> is traveling. The third vector can be in a direction opposite of a direction of the fourth vector. The visible electromagnetic radiation source 114c can be a component of the same system as or a component of a different system from the NIR electromagnetic radiation source 114a. The source <NUM> can comprise an automobile, the visible electromagnetic radiation source 114c can comprise a headlight of the automobile, and the NIR electromagnetic radiation source 114a and NIR detector 114b can be part of a LIDAR system.

Due to the minimal, if any, absorption or scattering of the visible electromagnetic radiation <NUM> by the coating <NUM> the returned visible electromagnetic radiation <NUM> has a substantially similar magnitude compared to a magnitude of the visible electromagnetic radiation <NUM>. The substantially similar magnitude can enable observation of the retroreflective substrate <NUM> by an operator and/or a visible electromagnetic radiation detector.

The coating <NUM> can be suitable to scatter and/or absorb NIR electromagnetic radiation and reduce the NIR retroreflectance of the retroreflective substrate <NUM>. The NIR retroreflectance of the retroreflective substrate <NUM> can be reduced by <NUM>% or greater such as, reduced by <NUM>% or greater, reduced by <NUM>% or greater, reduced by <NUM>% or greater, reduced by <NUM>% or greater, reduced by <NUM>% or greater, reduced by <NUM>% or greater, reduced by <NUM>% or greater, or reduced by <NUM>% or greater. The NIR retroreflectance of the retroreflective substrate <NUM> can be reduced by <NUM>% or lower, such as, reduced by <NUM>% or lower, reduced by <NUM>% or lower, reduced by <NUM>% or lower, reduced by <NUM>% or lower, reduced by <NUM>% or lower, reduced by <NUM>% or lower, reduced by <NUM>% or lower, or reduced by <NUM>% or lower. The reduction in NIR retroreflectance of the retroreflective substrate <NUM> can be in a range of <NUM>% to <NUM>%, such as, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%, or <NUM>% to <NUM>%.

The NIR retroreflectance of the retroreflective substrate <NUM> can be reduced in a wavelength range of <NUM> to <NUM>, such as, <NUM> to <NUM>. The NIR retroreflectance of the retroreflective substrate <NUM> can be reduced at various NIR wavelengths, such as, <NUM> and/or <NUM>. The coating <NUM> can absorb and/or scatter the <NUM> wavelength and/or the <NUM> wavelength. The coating <NUM> comprises a <NUM> absorbance of <NUM> absorbance unit(s) (Au) or greater, such as, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, or <NUM> Au or greater. The coating <NUM> can comprise a <NUM> absorbance of <NUM> Au or lower, such as, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, or <NUM> Au or lower. The coating <NUM> can comprise a <NUM> absorbance in the range of <NUM> Au to <NUM> Au, such as, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, or <NUM> Au to <NUM> Au.

The coating <NUM> comprises a <NUM> absorbance of <NUM> Au or greater, such as, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, <NUM> Au or greater, or <NUM> Au or greater. The coating <NUM> can comprise a <NUM> absorbance of <NUM> Au or lower, such as, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, <NUM> Au or lower, or <NUM> Au or lower. The coating <NUM> can comprise a <NUM> absorbance in the range of <NUM> Au to <NUM> Au, such as, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, <NUM> Au to <NUM> Au, or <NUM> Au to <NUM> Au.

As used herein, an "absorbance unit" or "Au" refers to a base <NUM> logarithm of a ratio of the electromagnetic radiation received by a substance to the electromagnetic radiation transmitted by the substance.

Minimal, if any, absorption or scattering of visible electromagnetic radiation by the coating <NUM> coupled with substantial adsorption and/or scattering of NIR electromagnetic radiation by the coating <NUM>, can enable the coating <NUM> to reduce the NIR retroreflectance of the retroreflective substrate <NUM> greater than the visible retroreflectance of the retroreflective substrate <NUM>. The coating <NUM> comprises a ratio of reduction in electromagnetic radiation retroreflectance at a wavelength of <NUM> and/or <NUM> to reduction in electromagnetic radiation retroreflectance averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> or greater, such as, <NUM>:<NUM> or greater, <NUM>:<NUM> or greater, or <NUM>:<NUM> or greater. The coating <NUM> can comprise a ratio of reduction in electromagnetic radiation retroreflectance at a wavelength of <NUM> and/or <NUM> to reduction in electromagnetic radiation retroreflectance averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> or lower, such as, <NUM>:<NUM> or lower, <NUM>:<NUM> or lower, or <NUM>:<NUM> or lower. The coating <NUM> can comprise a ratio of reduction in electromagnetic radiation retroreflectance at a wavelength of <NUM> and/or <NUM> to reduction in electromagnetic radiation retroreflectance averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> to <NUM>:<NUM> such as, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>. The reduction in electromagnetic radiation retroreflectance can be based on the retroreflectance of the retroreflective substrate <NUM> devoid of the coating <NUM>. For example, the reduction in retroreflectance can be determined by measuring the retroreflectance of the retroreflective substrate <NUM> devoid of the coating <NUM>, measuring the retroreflectance of the article <NUM> comprising both the retroreflective substrate <NUM> and the coating <NUM>, and determining the difference between the two measurements.

The coating <NUM> can comprise a ratio of electromagnetic radiation extinction at a wavelength of <NUM> and/or <NUM> to electromagnetic radiation extinction averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> or greater, such as, <NUM>:<NUM> or greater, <NUM>:<NUM> or greater, or <NUM>:<NUM> or greater. The coating <NUM> can comprise a ratio of electromagnetic radiation extinction at a wavelength of <NUM> and/or <NUM> to electromagnetic radiation extinction averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> or lower, such as, <NUM>:<NUM> or lower, <NUM>:<NUM> or lower, or <NUM>:<NUM> or lower. The coating <NUM> can comprise a ratio of electromagnetic radiation extinction at a wavelength of <NUM> and/or <NUM> to electromagnetic radiation extinction averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> to <NUM>:<NUM> such as, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>.

The reduction in electromagnetic radiation retroreflectance in the NIR range and the increase in electromagnetic extinction can be a result of NIR absorption and/or NIR scattering. The coating <NUM> can comprise a ratio of electromagnetic radiation absorption at a wavelength of <NUM> and/or <NUM> to electromagnetic radiation absorption averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> or greater, such as, <NUM>:<NUM> or greater, <NUM>:<NUM> or greater, or <NUM>:<NUM> or greater. The coating <NUM> can comprise a ratio of electromagnetic radiation absorption at a wavelength of <NUM> and/or <NUM> to electromagnetic radiation absorption averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> or lower, such as, <NUM>:<NUM> or lower, <NUM>:<NUM> or lower, or <NUM>:<NUM> or lower. The coating <NUM> can comprise a ratio of electromagnetic radiation absorption at a wavelength of <NUM> and/or <NUM> to electromagnetic radiation absorption averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> to <NUM>:<NUM> such as, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>.

The coating <NUM> can comprise a ratio of electromagnetic radiation scattering at a wavelength of <NUM> and/or <NUM> to electromagnetic radiation scattering averaged over a wavelength range of <NUM> to <NUM> of at least <NUM>:<NUM>, such as, <NUM>:<NUM>, at least <NUM>:<NUM>, or at least <NUM>:<NUM>. The coating <NUM> can comprise a ratio of electromagnetic radiation scattering at a wavelength of <NUM> and/or <NUM> to electromagnetic radiation scattering averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> or lower, such as, <NUM>:<NUM> or lower, <NUM>:<NUM> or lower, or <NUM>:<NUM> or lower. The coating <NUM> can comprise a ratio of electromagnetic radiation scattering at a wavelength of <NUM> and/or <NUM> to electromagnetic radiation scattering averaged over a wavelength range of <NUM> to <NUM> of <NUM>:<NUM> to <NUM>:<NUM> such as, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, <NUM>:<NUM> to <NUM>:<NUM>, or <NUM>:<NUM> to <NUM>:<NUM>. The electromagnetic radiation absorption, electromagnetic radiation scattering, electromagnetic radiation extinction, electromagnetic radiation transmittance, and electromagnetic radiation retroreflectance of the coating <NUM> can be measured in the cured state of the coating <NUM>.

As used herein, "average over a wavelength range of <NUM> to <NUM>" can include measuring a parameter (e.g., retroreflectance, extinction, absorption, scattering, transmittance) over the wavelength range of <NUM> to <NUM> in <NUM> steps (e.g., <NUM> total measurements) and then taking an average of the measurements.

The scattering and/or absorption of visible electromagnetic radiation by the coating <NUM> can affect the observed color of the retroreflective substrate <NUM>. A visible color of the retroreflective substrate <NUM> with the coating <NUM> and a visible color of the retroreflective substrate <NUM> without the coating <NUM> can be compared to determine a color difference, ΔE. The color difference, ΔE, can be minimized in order to limit observable visible color changes to the retroreflective substrate <NUM> after deposition of the coating composition to form coating <NUM>.

The color difference, ΔE, can be measured using the International Commission on Illumination L*a*b* (CIELAB) color space. The CIELAB color difference, ΔE, values reported herein are determined using an integrating sphere with D65 Illumination, <NUM>° observer with specular component included according to ASTM E308 unless otherwise stated. The CIELAB color difference, ΔE, is the difference between two colors in the CIELAB color space based on the difference between collected values of L*, a*, and b* according to Equation <NUM>.

The coating <NUM> can have a CIELAB color difference, ΔE, of the visible color of the retroreflective substrate without the coating <NUM> compared to the visible color of the retroreflective substrate with the coating of <NUM> or lower, such as, <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, or <NUM> or lower, all as measured using an integrating sphere with D65 Illumination, <NUM>° observer with specular component included. The coating <NUM> can have a CIELAB color difference, ΔE, of the visible color of the retroreflective substrate without the coating <NUM> compared to the visible color of the retroreflective substrate with the coating <NUM> of <NUM> or greater, such as, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, <NUM> or greater, or <NUM> or greater, all as measured using an integrating sphere with D65 Illumination, <NUM>° observer with specular component included. The coating <NUM> can have a CIELAB color difference, ΔE, of the visible color of the retroreflective substrate without the coating <NUM> compared to the visible color of the retroreflective substrate with the coating <NUM> in a range of <NUM> to <NUM>, such as, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, all as measured using an integrating sphere with D65 Illumination, <NUM>° observer with specular component included.

The present disclosure will be more fully understood by reference to the following examples, which provide illustrative non-limiting aspects of the invention. It is understood that the invention described in this specification is not necessarily limited to the examples described in this section.

As used herein, the term "Mw" refers to the average molecular weight and means the theoretical value as determined by Gel Permeation Chromatography using Waters <NUM> separation module with a Waters <NUM> differential refractometer (RI detector) and polystyrene standards. The Mw values reported according to the present disclosure were determined using this method. Tetrahydrofuran was used as the eluent at a flow rate of <NUM> min-<NUM>, and two PL Gel Mixed C columns were used for separation.

As used herein, the term "parts" refers to parts by weight unless indicated to the contrary.

To prepare polymer A, charge <NUM> was added to a round bottom flask equipped with a stirrer, condenser, temperature control system, and two feeding lines under inert gas. The reaction mixture was heated to <NUM> with stirring. Charge <NUM> was mixed together and added into the reaction mixture over <NUM> minutes. At the same time, charge <NUM> was added into the reaction mixture over <NUM> minutes. When the addition of charge <NUM> and <NUM> were completed, charge <NUM> was used to rinse charge <NUM> and <NUM>. After addition of charge <NUM>, an additional spike (charge <NUM>) of initiator was added to the reaction mixture over one hour and stirring was continued for one hour at reflux conditions. After completion of stirring charge <NUM> was added and the reaction mixture was cooled to <NUM>. At <NUM>, charge <NUM> was added into reaction mixture and stirring continued for one hour. After completion of stirring, the reaction mixture was cooled to <NUM>. At <NUM>, charge <NUM> was added into the reaction mixture and the stirring continued for <NUM> minutes. After stirring at <NUM>, charge <NUM> was added into reactor over one hour. After addition of charge <NUM>, the reaction mixture was poured out. The solid of acrylic polymer A is <NUM> % by weight and the Mw of polymer A is <NUM>.

To prepare polymer B, charge <NUM> was added to a round bottom flask equipped with a stirrer, condenser, temperature control system, and two feeding lines under inert gas. <NUM> % by weight of charge <NUM> and <NUM> % by weight of charge <NUM> were added into the reaction mixture of charge <NUM> at the same time. The reaction mixture was heated to reflux (<NUM>) with stirring. The remainder of charge <NUM> and charge <NUM> were added into the reaction mixture over two hours separately. After addition of charge <NUM> and charge <NUM>, charge <NUM> was used to rinse the feed lines of both charges <NUM> and <NUM>. At reflux conditions, an additional spike (charge <NUM>) of initiator was added to the reaction mixture over three hours. After addition of charge <NUM>, charge <NUM> was used to rinse and stirring was continued for <NUM> minutes at reflux conditions. After stirring completed, heat was off and charge <NUM> was added into reaction mixture. At <NUM>, charge <NUM> was added into reactor to cool the reaction mixture to <NUM>. The solid of acrylic polymer B is <NUM> % by weight and the Mw of polymer B is <NUM>.

To prepare coating ATO-<NUM>, <NUM> parts Antimony Tin Oxide (ATO) (e.g., pigment), (SN902SD, Nano Technologies Inc. ) were mixed with <NUM> parts polymer A, <NUM> parts n-butyl acetate, and <NUM> parts Zirconox milling media (<NUM>-<NUM> Zirconox milling beads, JYOTI Ceramics. The mixture was dispersed by shaking in a DAS <NUM> disperser (Lau GmbH) for four hours, and the milling media was removed by filtering with a <NUM> paper cone filter. Then <NUM> parts of the ATO dispersion was mixed with <NUM> parts TMAC9000FR clearcoat (available from PPG, Pittsburgh, Pennsylvania) (e.g., film-forming resin) to form coating ATO-<NUM> and drawdown on a transparent Mylar film using a #<NUM> wire-wound drawdown bar from RD Specialties, Webster, New York, resulting in a wet film thickness of <NUM> mils (<NUM>).

To prepare coating ATO-<NUM>, <NUM> parts ATO (e.g., pigment) were mixed with <NUM> parts of an acrylic dispersant as described in U. Patent No. <NUM>,<NUM>,<NUM> (Synthesis Example A), <NUM> parts n-butyl acetate, and <NUM> parts glass beads (<NUM> Spheriglass, Part number <NUM> from Potters Industries, LLC). The mixture was dispersed by shaking in a DAS <NUM> disperser (Lau GmbH) for <NUM> hours, and the glass beads were removed by filtering with a <NUM> bag filter (<NUM>-NMP <NUM> X1R-B, Brown and O'Malley Co. Then, <NUM> parts of the solution was mixed with <NUM> parts TMAC9000FR clearcoat to form coating ATO-<NUM> and drawdown on a transparent Mylar film using a #<NUM> wire-wound drawdown bar from RD Specialties resulting in a wet film thickness of <NUM> mils (<NUM>).

The ATO-containing coatings ATO-<NUM> and ATO-<NUM> were tested for transmittance and extinction utilizing a Perkin Elmer Lambda 950UV-Vis NIR spectrometer, and the results of the transmittance are plotted in <FIG> and the results of the extinction are plotted in <FIG>. The coatings ATO-<NUM> and ATO-<NUM> have a strong NIR electromagnetic radiation extinction, including an extinction at <NUM> and <NUM>. The coatings ATO-<NUM> and ATO-<NUM> reduced <NUM> transmission by <NUM>% and <NUM> transmission by <NUM>% while maintaining <NUM>%-<NUM>% visible transmission averaged over the visible range of the electromagnetic spectrum.

Particle size of the milled ATO was analyzed by dynamic light scattering, using a Nano ZS instrument manufactured by Malvern, Westborough, Massachusetts. ATO-<NUM> was determined to have an average particle size of <NUM>, and ATO-<NUM> was <NUM>. Due to the use of longer grind time, finer media size, and different dispersant, ATO-<NUM> has a smaller particle size than ATO-<NUM>.

Extinction was calculated based on percent transmission, and the results are shown in Table <NUM> herein. Extinction (E) can be calculated from percent transmission (%T) according to Equation <NUM>.

Percent transmission (%T) can be calculated from Extinction (E) according to Equation <NUM>.

Coating ATO-<NUM> has a higher ratio of NIR electromagnetic extinction to visible electromagnetic extinction versus coating ATO-<NUM>. The higher ratio suggests that reducing particle size to nanoscale was effective at increasing the ratio of NIR electromagnetic radiation extinction to visible electromagnetic radiation extinction as measured at <NUM>, Ex<NUM>/Exvis, and <NUM>, Ex<NUM>/Exvis. It is believed that a further reduction in particle size may additionally increase the ratio of NIR electromagnetic radiation extinction to visible electromagnetic radiation extinction, and other pigments may exhibit an increase in the ratio of NIR electromagnetic radiation extinction to visible electromagnetic radiation extinction by reducing particle size. It is believed that coatings containing ATO have a reduced NIR transmittance via extinction of NIR electromagnetic radiation.

As used herein, "Ex<NUM>/Exvis" is defined to refer to the ratio of electromagnetic radiation extinction at <NUM> to the averaged electromagnetic radiation extinction over the visible range of <NUM> to <NUM> with measurements taken in <NUM> steps. As used herein, "Ex<NUM>/Exvis" is defined to refer to the ratio of electromagnetic radiation extinction at <NUM> to the averaged electromagnetic radiation extinction over the visible range of <NUM> to <NUM> with measurements taken in <NUM> steps.

To prepare coating LaB<NUM>-<NUM>, <NUM> parts LaB<NUM> (Skysprings Nanomaterials Inc. , <NUM>+%, average particle size (APS): <NUM>-<NUM>) was mixed with <NUM> parts polymer A and <NUM> parts n-butyl acetate and <NUM> parts Zirconox milling media (<NUM>-<NUM> Zirconox milling beads, JYOTI Ceramics. The mixture was dispersed by shaking in a DAS <NUM> disperser (Lau GmbH) for four hours, and the milling media was removed by filtering with a <NUM> paper cone filter. Then <NUM> parts of the obtained LaB<NUM> dispersion was mixed with <NUM> parts TMAC9000FR clearcoat to form coating LaB<NUM>-<NUM> and drawdown using a #<NUM> wire-wound drawdown bar from RD Specialties on a transparent Mylar film resulting in a wet film thickness of <NUM> mils (<NUM>).

To prepare coating LaB<NUM>-<NUM>, <NUM> parts LaB<NUM> (Skysprings Nanomaterials Inc. , <NUM>+%, APS: <NUM>-<NUM>) were mixed with an acrylic dispersant as described in <CIT> (Synthesis Example A), <NUM> parts n-butyl acetate, and <NUM> parts glass beads (<NUM> Spheriglass, Part number <NUM> from Potters Industries, LLC). The mixture was dispersed by shaking in a DAS <NUM> disperser (Lau GmbH) for <NUM> hours, and the media was removed by filtering with a <NUM> bag filter (<NUM>-NMP <NUM> X1R-B, Brown and O'Malley Co. Then <NUM> parts of the LaB<NUM> dispersion was mixed with <NUM> parts TMAC9000FR clearcoat to form coating LaB<NUM>-<NUM> and drawdown on a transparent Mylar film using a #<NUM> wire-wound drawdown bar from RD Specialties resulting in a wet film thickness of <NUM> mils (<NUM>).

The LaB<NUM>-containing coatings LaB<NUM>-<NUM> and LaB<NUM>-<NUM> were tested for transmittance and extinction utilizing a Perkin Elmer Lambda 950UV-Vis NIR spectrometer, and the transmittance results are plotted in <FIG> and the extinction results are plotted in <FIG>. LaB<NUM>-containing coatings LaB<NUM>-<NUM> and LaB<NUM>-<NUM> have a strong extinction near <NUM>. Due to the use of longer grind time, finer media size and different dispersant, coating LaB<NUM>-<NUM> has a smaller particle size than coating LaB<NUM>-<NUM>. Dynamic light scattering measurement, using a Nano ZS instrument, shows that LaB<NUM>-<NUM> has an average particle size of <NUM>, much smaller than LaB<NUM>-<NUM> with <NUM> particles. As shown in Table <NUM>, coating LaB<NUM>-<NUM> had a higher ratio of NIR electromagnetic radiation extinction to visible electromagnetic radiation extinction than coating LaB<NUM>-<NUM>. Similar to the case of ATO, the result demonstrates that reducing the particle size to nanoscale increases the ratio of NIR electromagnetic radiation extinction to visible electromagnetic radiation extinction as measured at <NUM>, Ex<NUM>/Exvis, and <NUM>, Ex<NUM>/Exvis.

The LaB<NUM>-<NUM> films reduced <NUM> transmission by <NUM>% while maintaining more than <NUM>% (<NUM>% reduction) visible transmission. Coating LaB<NUM>-<NUM> resulted in a ratio of reduction in NIR transmittance (e.g., LIDAR signal wavelength) to visible transmittance of <NUM>. It is believed that coatings containing LaB<NUM> reduce the NIR transmittance via extinction of NIR electromagnetic radiation.

<NUM> parts LaB<NUM> powder (e.g., pigment) (Skysprings Nanomaterials Inc. , <NUM>+%, APS: <NUM>-<NUM>) was mixed with <NUM> parts acrylic resin as described in <CIT> (Synthesis Example A), <NUM> parts glass beads (<NUM> Spheriglass, Part number <NUM> from Potters Industries, LLC), and <NUM> parts n-butyl acetate. The mixture was dispersed in a DAS <NUM> disperser (Lau GmbH) for <NUM> hours, and the glass beads were removed by filtering with a <NUM> bag filter (<NUM>-NMP <NUM> X1R-B, Brown and O'Malley Co. ) to form a LaB<NUM> dispersion.

<NUM> parts of the LaB<NUM> dispersion were mixed with <NUM> parts DC2000 refinish clearcoat (available from PPG, Pittsburgh, Pennsylvania) and <NUM> parts n-butyl acetate to formulate a coating LaB<NUM>-<NUM>. <NUM> parts of LaB<NUM> dispersion were mixed with <NUM> parts DC2000 refinish clearcoat and <NUM> parts n-butyl acetate to formulate a coating LaB<NUM>-<NUM>. Liquid coating LaB<NUM>-<NUM> and LaB<NUM>-<NUM> were each applied on a retroreflective sheet (Nikkalite <NUM>) by drawdown using a #<NUM> wire-wound drawdown bar from RD Specialties resulting in a wet film thickness of <NUM> mils (<NUM>). The coatings LaB<NUM>-<NUM> and LaB<NUM>-<NUM> were each cured on the respective retroreflective sheet at ambient conditions and were tested for LIDAR signal intensity and retroreflectivity. The LIDAR signal was tested with a LeddarVu <NUM> solid state LIDAR, which utilizes <NUM> NIR light source. The LIDAR signal was read at <NUM> detector-to-sample distance with laser intensity setting at <NUM>%. The visible retroreflectance (reflectivity) was evaluated with a <NUM> RoadVista retroreflectometer which is ASTM E1709 compliant.

For coating LaB<NUM>-<NUM> (e.g., contains <NUM>% by weight LaB<NUM>), the reduction in LIDAR signal is <NUM>% while visible retroreflectance is maintained at <NUM>% (<NUM> % reduction) with respect to uncoated retroreflective sheet. Coating LaB<NUM>-<NUM> resulted in a ratio of reduction in NIR retroreflectance (e.g., LIDAR signal) to visible retroreflectance of <NUM>. For coating LaB<NUM>-<NUM> (e.g., contains <NUM> % by weight LaB<NUM>), the reduction in LIDAR signal is <NUM>% while visible retroreflectance is maintained at <NUM>% (<NUM> % reduction) with respect to the uncoated retroreflective sheet. Coating LaB<NUM>-<NUM> resulted in a ratio of reduction in NIR retroreflectance (e.g., LIDAR signal) to visible retroreflectance of <NUM>.

To produce coating Ep-<NUM> (e.g., containing <NUM>% by weight Epolight <NUM> dye), <NUM> part Epolight <NUM> dye was dissolved in <NUM> parts methyl amyl ketone. Epolight <NUM> dye comprises a phthalocyanine dye. Then, <NUM> parts Epolight <NUM> dye solution was mixed with <NUM> parts DC2000 liquid clearcoat. The coating mixture was applied on a retroreflective sheet (Nikkalite <NUM>) via drawdown using a #<NUM> wire-wound drawdown bar from RD Specialties resulting in a wet film thickness of <NUM> mils (<NUM>). Coating EP-<NUM> was cured on the retroreflective sheet at ambient conditions and was tested for LIDAR signal intensity and retroreflectivity.

Coating Ep-<NUM> reduces <NUM>% LIDAR signal while visible retroreflectance is maintained at <NUM>% with respect to the uncoated retroreflective sheet. Coating Ep-<NUM> resulted in a ratio of reduction in NIR retroreflectance (e.g., LIDAR signal) to visible retroreflectance of greater than <NUM>.

Coating Al-<NUM> was prepared and tested for a ratio of reduction in NIR retroreflectance (e.g., LIDAR signal) to visible retroreflectance. <NUM> parts Alumina powder (<NUM> spherical particles, 26R-8S05, Inframat) (e.g., pigment) was mixed with <NUM> parts acrylic resin Polymer B and <NUM> parts n-butyl acetate solvent. The mixture was stirred for <NUM> minutes to obtain an alumina dispersion.

<NUM> parts alumina dispersion was mixed with <NUM> parts DC2000 clearcoat, and the mixture was drawdown on a retroreflective sheet using a #<NUM> wire-wound drawdown bar from RD Specialties. Coating Al-<NUM> was cured on the retroreflective sheet at ambient conditions and was tested for LIDAR signal intensity and retroreflectivity.

Coating Al-<NUM> reduces LIDAR signal by <NUM>% while visible retroreflectance is maintained at <NUM>% (<NUM>% reduction) with respect to the uncoated retroreflective sheet. Coating Al-<NUM> resulted in a ratio of reduction in NIR retroreflectance (e.g., LIDAR signal) to visible retroreflectance of <NUM>. It is believed that coating Al-<NUM> reduced the NIR retroreflectance via scattering of NIR electromagnetic radiation.

To produce coating Au-<NUM>, <NUM> parts aqueous dispersion of Au nanorods (<NUM>/mL, A12-<NUM>-<NUM>-CTAB, Nanopartz) was mixed with <NUM> part resin (<CIT> Example <NUM>). The solution was drop-cast onto a Mylar substrate. Coating Au-<NUM> was cured on the retroreflective sheet at ambient conditions.

Coating Au-<NUM> was tested for transmittance utilizing a Vernier Go Direct SpectroVis Plus spectrometer, and the transmittance results are plotted in <FIG>. The NIR transmission drops to <NUM>% (<NUM>% reduction) and visible transmission is above <NUM>% (<NUM>% reduction). The coating Au-<NUM> containing Au nanorods results in a ratio of reduction in NIR transmittance (e.g., LIDAR signal wavelength) to visible transmittance of greater than <NUM>.

Coating LaB<NUM>-<NUM> and coating Ep-<NUM> were tested for weather-ability. The coatings were cured on a white colored aluminum panel (Tru aluminum 04X12X038, unpolished, white, APT33676, Batch: <NUM>, ACT Laboratories Inc. ) and placed into a weather-o-meter (following SAE J2527) for <NUM> to <NUM> hours. Then, the film was tested for reflectivity utilizing a Perkin Elmer Lambda 950UV-Vis NIR spectrometer. The NIR electromagnetic radiation extinction of the coating Ep-1containing films deteriorated quickly such that after <NUM>, no pronounced electromagnetic radiation extinction can be seen in the NIR. After <NUM> hours of weathering, coating LaB<NUM>-<NUM> did not have an observable NIR electromagnetic radiation extinction signal deterioration as shown in <FIG>. It is believed that the pigment in LaB<NUM>-<NUM> enables the enhanced weather resistance as compared to coating Ep-<NUM> which contains a dye.

Coating LaB<NUM>-<NUM> was sprayed over stop signs (engineering-grade official MUTCD stop signs, RoadTrafficSigns. A stainless steel substrate was sprayed at the same time for determination of dry film thickness with a Deltascope MP30.

An integrating sphere spectrophotometer (Minolta CM-3600d) with D65 Illumination, <NUM>° observer with specular component included according to ASTM E308 was used to evaluate the color difference, CIELAB ΔE, of the coating LaB<NUM>-<NUM>. Values of ΔE were calculated according to Equation <NUM> and are shown in Table <NUM>.

As shown in Table <NUM>, coating LaB<NUM>-<NUM> reduced the NIR retroreflectance of the retroreflective substrate and maintained a sufficient level of visible retroreflectance and as shown in Table <NUM>. The coating LaB<NUM>-<NUM> did not significantly alter the color of the substrate (e.g., stop sign). It is believed that other coatings formulations according to the present disclosure also can achieve a reduction in NIR retroreflectance, can maintain a sufficient level of visible retroreflectance, and may not significantly alter the color of the underlying layers or substrate.

One skilled in the art will recognize that the herein described compositions, articles, methods, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken as limiting.

With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like "responsive to," "related to," or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise.

Although various examples have been described herein, many modifications, variations, substitutions, changes, and equivalents to those examples may be implemented and will occur to those skilled in the art. Also, where materials are disclosed for certain components, other materials may be used. It is therefore to be understood that the foregoing description and the appended claims are intended to cover all such modifications and variations as falling within the scope of the disclosed examples. The following claims are intended to cover all such modification and variations.

Any numerical range recited in this specification describes all sub-ranges of the same numerical precision (i.e., having the same number of specified digits) subsumed within the recited range. For example, a recited range of "<NUM> to <NUM>" describes all sub-ranges between (and including) the recited minimum value of <NUM> and the recited maximum value of <NUM>, such as, for example, "<NUM> to <NUM>," even if the range of "<NUM> to <NUM>" is not expressly recited in the text of the specification.

Also, unless expressly specified or otherwise required by context, all numerical parameters described in this specification (such as those expressing values, ranges, amounts, percentages, and the like) may be read as if prefaced by the word "about," even if the word "about" does not expressly appear before a number. Additionally, numerical parameters described in this specification should be construed in light of the number of reported significant digits, numerical precision, and by applying ordinary rounding techniques. It is also understood that numerical parameters described in this specification will necessarily possess the inherent variability characteristic of the underlying measurement techniques used to determine the numerical value of the parameters.

Notwithstanding that numerical ranges and parameters setting forth the broad scope of the invention are approximations, numerical values are set forth in the specific examples are reported precisely as possible.

The invention(s) described in this specification can comprise, consist of, or consist essentially of the various features and characteristics described in this specification. The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), "include" (and any form of include, such as "includes" and "including"), and "contain" (and any form of contain, such as "contains" and "containing") are open-ended linking verbs. Thus, a composition, coating, or method that "comprises," "has," "includes," or "contains" one or more features and/or characteristics possesses those one or more features and/or characteristics but is not limited to possessing only those one or more features and/or characteristics. Likewise, an element of a composition, coating, or process that "comprises," "has," "includes," or "contains" one or more features and/or characteristics possesses those one or more features and/or characteristics but is not limited to possessing only those one or more features and/or characteristics and may possess additional features and/or characteristics.

The grammatical articles "a," "an," and "the," as used in this specification, including the claims, are intended to include "at least one" or "one or more" unless otherwise indicated. Thus, the articles are used in this specification to refer to one or more than one (i.e., to "at least one") of the grammatical objects of the article. By way of example, "a component" means one or more components, and thus, possibly more than one component is contemplated and can be employed or used in an implementation of the described compositions, coatings, and processes. Nevertheless, it is understood that use of the terms "at least one" or "one or more" in some instances, but not others, will not result in any interpretation where failure to use the terms limits objects of the grammatical articles "a," "an," and "the" to just one. Further, the use of a singular noun includes the plural, and the use of a plural noun includes the singular, unless the context of the usage requires otherwise.

Whereas particular examples of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.

Claim 1:
A coating composition, comprising:
A film-forming resin; and
a pigment suitable to absorb and/or scatter electromagnetic radiation in a wavelength range of <NUM> to <NUM>,
wherein the pigment comprises zinc oxide, alumina, antimony tin oxide, tungsten oxide, gold nanoparticles, silver nanoparticles, copper nanoparticles, lanthanum hexaboride, dicopper hydroxide phosphate, a phthalocyanine, or a combination thereof;
wherein a coating formed from the coating composition comprises a ratio of reduction in electromagnetic radiation retroreflectance at a wavelength of <NUM> and/or <NUM> to reduction in electromagnetic radiation retroreflectance averaged over a wavelength range of <NUM> to <NUM> of at least <NUM>:<NUM>;
wherein the coating absorbs at least <NUM> absorbance units of electromagnetic radiation at a wavelength of <NUM>; and/or
wherein the coating absorbs at least <NUM> absorbance units of electromagnetic radiation at a wavelength of <NUM>.