Optical device for controlling color attributes

Abstract

To provide an optical device that is engineered to address one or more, such as all, of limitations faced by the approach associated with colorants used for decorative applications, in which approach, the colorants in use come in the form of pigments that are predominantly formed by grinding or milling various colored inorganic or organic materials into desired particle sizes, resulting in the problematic limitations including, for example, that there are limited choices of materials capable of yielding pigments that combine desired colors and specific functional attributes such as lightfastness, chroma, hiding power, environmental stability and toxicity profile.SOLUTION: There is disclosed an optical device 10 comprising: a host material 20 including an optically transparent material; at least one organic colorant 30 in the host material; and at least one additive. The optical device is a particle having a lamellar shape. There are also disclosed compositions including the optical device and methods of manufacturing the optical device.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] (Related Applications) This application claims priority to U.S. Provisional Application No. 63 / 625,496, filed January 26, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to optical devices, methods of making optical devices, and compositions comprising optical devices. [Background technology]

[0003] Currently, most colorants used in decorative applications are primarily in the form of pigments, formed by grinding or milling various colored inorganic or organic materials to the desired particle size. This method has several limitations. For example, the selection of materials from which pigments can be obtained that combine the desired color and specific functional attributes, such as lightfastness, saturation, hiding power, environmental stability, and toxicity profile, is limited. In particular, the majority of pigments approved for use in various environmentally demanding applications, such as the automotive, marine, and aviation markets, cannot be used in very small particle sizes of organic pigments due to their reduced lightfastness. As understood in the pigment industry, the lightfastness of organic pigments decreases at particle sizes below approximately 100 nm. This is also the reason why dyes are not used in masstone applications, as they not only fail to achieve lightfastness targets but also exhibit many other issues, such as chemical stability and migration (bleeding) from the carrier system. This limitation on pigment particle size has a detrimental effect on the optical effects achievable with colorants, such as pigment flop, light scattering, and hiding power. Summary of the Invention [Problem to be solved by the invention]

[0004] Additionally, some historically established pigment systems have recently come under scrutiny due to their toxicity profiles and are being phased out, further limiting the colorant options available to coating companies and OEMs to create new and compelling color concepts.

[0005] What is needed is an optical device designed to address one or more of the aforementioned limitations, such as all of them. [Brief explanation of the drawings]

[0006] Features of the present disclosure are illustrated by way of example, and not by way of limitation, in the following figures, in which like numerals refer to like elements and in which: [Figure 1] 1 shows a composition including a pigment. [Figure 2] 1 shows a schematic cross-sectional view of a layered optical device in a composition according to one embodiment of the present disclosure. [Figure 3] 1 shows a schematic cross-sectional view of a layered optical device according to one aspect of the present disclosure. [Figure 4] 1 shows a schematic cross-sectional view of a layered optical device on a substrate including a release layer according to one aspect of the present disclosure. [Figure 5] 1 shows a grayscale image of a colored composition comprising a layered optical device according to one embodiment of the present disclosure. [Figure 6] 1 shows a grayscale image of a colored composition comprising a layered optical device according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0007] In one aspect, an optical device is disclosed, the optical device comprising: a host material made of an optically transparent material; at least one organic colorant in the host material; and at least one additive, the optical device being a particle having a layered shape.

[0008] In one aspect, a method of making an optical device is disclosed, the method comprising combining at least one organic colorant, at least one additive, and a liquid matrix to form a coating composition, wherein the at least one organic colorant has a D50 particle size of less than 100 nm, depositing the coating composition onto a substrate using a liquid coating process, solidifying the matrix to form a solid layer, detaching the substrate from the solid layer, and separating the solid layer into particles.

[0009] In another aspect, an optical device is disclosed, the optical device comprising: a matrix in layered form having a first major surface and a second major surface opposite the first major surface, the matrix comprising an optically transparent material; at least one organic colorant in the matrix; and at least one additive, wherein the at least one organic colorant has a D50 particle size of less than 100 nm.

[0010] Additional features and advantages of various embodiments will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of various embodiments. The objectives and other advantages of the various embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the description herein.

[0011] (Detailed explanation) For purposes of simplicity and illustration, the present disclosure will be described primarily with reference to its exemplary embodiments. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be readily apparent that the present disclosure may be practiced without being limited to these specific details. In other instances, some methods and structures have not been described in detail so as not to unnecessarily obscure the present disclosure.

[0012] Additionally, the elements depicted in the accompanying figures may include additional components, and some of the components depicted in these figures may be removed and / or modified without departing from the scope of the present disclosure. Additionally, the elements depicted in the figures may not be drawn to scale, and therefore, elements may have a different size and / or configuration than that shown in the figures.

[0013] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide explanations of various embodiments of the present teachings.

[0014] The present application is directed to optical devices that include a host material, where the morphology of the host material can determine the shape and dimensions of the optical device. For example, the host material can be configured in the form of layered particles (e.g., flakes or platelets) to form a layered optical device of the same shape and size as the configured host material. The optical devices of the present application can incorporate one or more features into their structure that enhance their optical and non-optical properties. For example, the optical devices can be engineered at the particle level to provide one or more of lightfast pigments, high chroma pigments, pigments with high hiding power, and other advantages, as described in more detail herein. The optical devices of the present application provide an alternative to traditionally used powdered, high-performance organic and inorganic pigments. Other advantages of the optical devices of the present application include one or more of: controlling color properties at the particle level of the designed optical device; controlling light scattering at the particle level of the designed optical device in visible and / or invisible (UV, IR) wavelengths; controlling flop characteristics at the particle level of the designed optical device; controlling the hiding power of the designed layered optical device by adjusting particle thickness, colorant loading level in the host matrix material and / or colorant particle size; controlling adhesion of flakes to paint systems by introducing reactive functionality (e.g., adhesion improving compounds) into the host matrix material; providing stabilization functionality at the flake level that is not available at the paint system level; and / or providing stability and reliability at the optical device level for colorants that are not stable when placed in a paint or other composition without being incorporated into the host material of the optical device.

[0015] Referring to FIG. 2 , the present disclosure is directed to an optical device 10 that includes a host material 20. The host material 20 includes an optically transparent material. At least one organic colorant 30 is included in the host material 20. The optical device further includes at least one additive (not shown), which may be included in or otherwise adhered to the host material 20. The phrase “at least one” is equivalent to the phrase “one or more,” and either phrase can be substituted for the other throughout this application (e.g., “at least one colorant” is intended to mean the same as “one or more colorants”).

[0016] The matrix 20 can be an optically transparent material that can be configured to define the shape of the optical device 10. In one embodiment, the matrix 20 can be in the form of layered particles, such as flakes or platelets. The layered particles can include one or more layers of matrix, as described in detail herein. As described herein, the matrix 20 can act as a matrix into which at least one organic colorant 30 is mixed and / or dispersed. At least one additive can also be included in or attached to the surface of the matrix 20.

[0017] The matrix 20 can be in the form of a solid layer having a first major surface 40 and a second major surface 40 opposite the first major surface. In one embodiment, the first major surface and the second major surface are the outermost surfaces of the optical device 10. In one embodiment, the optical device 10 has the same matrix throughout the entire thickness "a" of the optical device 10 (see, e.g., FIG. 3). For example, the optical device 10 can include only a single layer of matrix 20, e.g., the single layer can have the same at least one colorant and at least one additive dispersed throughout the single layer, and the thickness of the single layer is the same as the entire thickness of the optical device 10.

[0018] Alternatively, optical device 10 further comprises at least one additional solid layer comprising a matrix. The at least one additional solid layer and the first solid layer form stack 68, with each layer of the stack disposed on a major surface of an adjacent layer, as illustrated, for example, by layers 62, 64, and 66 in FIG. 4 . In one embodiment, stack 68 includes two or more adjacent layers of matrix 20 that make up the total thickness "a" of optical device 10. Matrix 20 may be the same or different for any two or more layers of the stack. For example, all layers of the stack may have the same matrix. In one embodiment, optical device 10 includes only the layers of stack 68, with the combined thickness of the layers (e.g., layers 62, 64, and 66) being the same as the total thickness of optical device 10.

[0019] The matrix 20 may be a dielectric material, such as at least one of an organic polymer, an inorganic polymer, and a composite material. Dielectric materials are electrically insulating and non-metallic. In one embodiment, the organic material may be at least one material selected from thermoplastics, thermosetting materials, and energy-curable materials. Non-limiting examples of organic polymers include thermoplastics, such as polyesters, polyolefins, polycarbonates, polyamides, polyimides, polyurethanes, acrylics, acrylates, polyvinyl esters, polyethers, polythiols, silicones, fluorocarbons, polyvinyl chloride, polystyrene, polyvinyl acetate, polyvinyl alcohol, and copolymers (e.g., styrene / acrylic copolymers), or blends thereof; thermosetting resins, such as acrylic / nitrocellulose blends and acrylic / epoxy hybrids, epoxies, polyurethanes, acrylates, melamine formaldehyde, urea formaldehyde, phenol formaldehyde, and copolymers or blends thereof; and energy-curable materials, such as acrylates, epoxies, vinyls, vinyl esters, styrenes, silanes, and copolymers or blends thereof. In one embodiment, the thermoplastic material can be selected from acrylic polymers, polyvinyl chloride, polystyrene, acrylic / nitrocellulose blends, acrylic / epoxy hybrids, styrene / acrylic, polyvinyl acetate, and polyvinyl alcohol. Non-limiting examples of inorganic polymers include silanes, siloxanes, titanates, zirconates, aluminates, silicates, phosphazanes, polyborazylenes, and polythiazyls. In some embodiments, the matrix comprises one or more polymers, such as any of the organic or inorganic polymers described herein for use as the matrix. In some embodiments, the one or more polymers are selected from acrylates, epoxies, and polyurethanes, and copolymers or blends thereof.

[0020] The host material can be present in the optical device in any suitable amount that provides the desired structural integrity, light resistance, optical properties, and / or other characteristics. In one embodiment, the host material 20 can be present in the optical device 10 in an amount ranging from about 5% to about 95% by weight, such as from about 10% to about 80% by weight, and as a further example, from about 20% to about 70% by weight, based on the weight of the optical device 10.

[0021] The function of the matrix 20 is to provide the body of the final layered optical device 10 with mechanical integrity. The matrix 20 also serves as a substrate in which the colorant 30 can be contained and additives can be dispersed or attached. Furthermore, by controlling moisture and oxygen permeability, the matrix protects the colorant 30 from harmful hydrolytic and oxidative attack. In some embodiments, the matrix 20 can provide a level of internal UV filtering to protect the organic colorant 30 from photochemical degradation. By appropriately matching the chemistry of the matrix with that of at least one organic colorant 30, such as the organic dyes and / or organic nanopigments described herein, the optical device 10 can reduce or prevent colorant leaching from the matrix system and / or reduce issues with colorant bleeding.

[0022] The selection of the host material can also affect the spectral characteristics, refractive index, mechanical properties, thermal properties, thermomechanical properties, environmental durability, chemical properties, and / or optical properties of the optical device 10. For example, the selection of the chemistry of the host material can engineer the loading level and degree of dispersion of colorants 30, such as organic dyes and nano-dispersed pigments, in the optical device 10. This can control the hiding power of optical devices with layered, engineered structures. It is worth noting that, if desired, the host material can be made of a material that meets stringent regulatory requirements and offers an attractive biocompatibility profile. As an example, the host material can be selected based on one or more of the following: cure mechanism, refractive index, hardness, thermomechanical properties, hydrolytic stability, chemical affinity for various organic dyes and / or pigment nanoparticles, and compatibility with different coating systems. As another example, the host material can be selected to provide protection against UV exposure and / or reduce moisture and oxygen ingress into the bulk of the optical device, thereby protecting the colorants incorporated therein. In another example, the engineered optical device 10 can be formed from a host material having a refractive index higher than the refractive index of a composition, such as a paint or other color composition, into which the engineered optical device is incorporated as a colorant. In one example, the host material can be employed to control the dispersion of the nanopigments within the engineered optical device and / or to control the dispersion of the engineered optical device within a composition, such as a paint or other color composition, into which the engineered optical device is to be incorporated.

[0023] The matrix 20 includes at least one organic colorant 30, such as an organic dye, an organic nanopigment (also referred to herein as an organic nano-dispersed pigment), or a combination thereof. Optionally, inorganic pigments can be employed in addition to the organic colorant, as described in more detail below. The at least one organic colorant 30 provides the desired color characteristics of the resulting optical device 10. By incorporating the at least one organic colorant 30 into the matrix 20, the lightfastness and / or environmental reliability of the at least one organic colorant 30 can be improved compared to using the same at least one organic colorant 30 directly in a matrix-free color composition 50, as shown in FIG. 1 . The at least one organic colorant 30 can include multiple (e.g., two, three, four, five, or more) different colorants with different hues in the matrix 20. For example, multiple organic nanopigments with different hues, multiple different organic dyes with different hues, or a combination of one or more organic nanopigments and one or more organic dyes can be employed in a single layer of the matrix 20.

[0024] In one aspect, the optical device 10 of the present application employs organic nanopigments as color-introducing materials. Organic nanopigments can have one or more advantages, such as well-defined spectral characteristics offering a wide selection of available colors and hiding powers, attractive pricing, multiple supply sources, known and well-understood chemistry / photochemistry, availability in nanoparticle form with different size ranges and size distribution specifications, wide acceptance across various markets, and known regulatory and ecological related profiles.

[0025] In one aspect of the present invention, dyes can be employed instead of or in addition to organic nanopigments. For example, for certain colors, such as yellow, orange, or red, a mixture of appropriate organic dyes combined with selected nano-sized pigments can be employed to enhance the lightfastness of the resulting optical device 10. There is a long list of organic dyes known for their attractive hues that can be used for this application. The organic dyes can be introduced and dispersed in the matrix at the molecular level or in a manner that allows the formation of aggregates of controlled shape and size.

[0026] As will be appreciated by those skilled in the art, the same colorant material can often be used as either a dye or a pigment, depending on whether the material is soluble in the solution used to fabricate optical device 10. If the colorant material is soluble in the solution employed to fabricate optical device 10, the colorant is considered a dye and may be included as dye molecules and / or aggregates of dye molecules in a host material. Alternatively, if the colorant material is insoluble in the solution employed to fabricate optical device 10, the colorant is considered a pigment and may be included as nanoparticles in a host material.

[0027] Any suitable organic colorant may be employed that is capable of providing the desired color effect and is compatible with the host material 20. Non-limiting examples of organic dye and organic nanopigment materials include perylenes, perinones, quinacridones, quinacridonequinones, anthrapyrimidines, anthraquinones, anthanthrones, benzimidazolones, disazo condensation pigments, disazo dyes, azo dyes, azo pigments, quinolones, xanthenes, azomethinequinophthalones, indanthrones, phthalocyanines, triarylcarboniums, dioxazines, aminoanthraquinones, isoindolines, diketopyrrolopyrroles (DPP), thioindigo, thiazineindigo, isoindolines, isoindolinones, pyranthrones, isoviolanthrones, miyoshimethane, triarylmethanes, and mixtures of two or more thereof.

[0028] In one embodiment, the organic nanopigments are selected from the following classes of compounds: benzimidazolone-derived pigments, diketopyrrolopyrrole (DPP) pigments, disazo condensation pigments, isoindoline, perylene pigments, and phthalocyanine pigments, and combinations thereof. These pigments can provide enhanced color and saturation. For example, benzimidazolone-derived pigments can be employed in a wide range of yellow and red hues; diketopyrrolopyrrole (DPP) pigments can be employed in reds as well as yellows and oranges; disazo condensation pigments can be employed in yellows, oranges, and reds; isoindoline pigments can be employed in lightfast yellows; perylene pigments can be employed in various red hues and blacks; and phthalocyanine pigments can be employed in lightfast blues and greens. These pigments offer excellent color space selectivity, chromaticity, and / or saturation. As an example, commercially available benzimidazolone-derived pigments such as PY151, PY154, PY181, PO36, PO181, and PY191 can provide a variety of attractive yellow and orange hues when used as single components or in mixtures. Examples of organic dyes include polymethine dyes, phthalocyanines, porphyrins, azo dyes, anthraquinone dyes, and combinations thereof. Any one or more of the dyes described above can be included in the host material of the optical device 10 in combination with any one or more of the organic nanopigments described above. The dyes and / or pigments can be employed to provide any desired hue, such as red, orange, yellow, green, and blue (e.g., hue angles from 0 to 360 on the CIELab color scale), as well as achromatic colors such as black, gray, and white.

[0029] In one embodiment, the organic colorants have a particle size of less than 100 nm. While the optical devices of the present invention can have certain advantages when very small organic colorant particle sizes, such as less than 100 nm, are employed, colorants outside this range can also be employed. For example, organic pigments with submicron particle sizes, such as 50 nm to 0.5 microns, can be employed. However, particles larger than 0.5 microns can cause undesirable light scattering effects. Therefore, in some embodiments, the organic colorants have a D99 of 0.5 microns or less (e.g., 99% or more of the organic colorant particles are 0.5 microns or less). The D99 size can generally be determined using the same equipment used to determine the D50 size of a colorant, as discussed herein.

[0030] In one embodiment, the organic colorants, such as any particles formed by nanopigments and / or dye aggregates, have a D50 particle size of less than 100 nm. In one embodiment, the D50 of nanoparticles can be smaller than the wavelength of light in their intended application. Any dye colorant can be in molecular form, such as individual dye molecules. Colorants in molecular form are understood to have a size of less than 100 nm. When the colorant is in particle form (e.g., nanopigments or aggregate dye particles), the colorant can have a D50 particle size of, for example, about 1 nm to less than 100 nm, or about 5 nm to about 90 nm, or about 10 nm to about 80 nm, or about 50 nm to less than 100 nm. Particle sizes, including D50 or D99 particle sizes, of the organic colorants herein can be measured using a Malvern Zetasizer, available from Malvern Panalytical, headquartered in Malvern, UK. TM In one embodiment, any of the organic colorants described herein can have both a D50 and a D99 selected from any of the D50 and D99 ranges described herein (e.g., a D50 of less than 100 nm and a D99 of 0.5 microns or less).

[0031] Any suitable organic colorant concentration can be employed in the host 20. For example, the at least one organic colorant 30 can have a total organic colorant concentration in the host 20 of from about 0.1% to about 50% by weight, such as from about 5% to about 40% by weight, or from about 10% to about 30% by weight, based on the total weight of the optical device. The total organic colorant concentration includes the total concentration of all organic colorants in the host, including organic dyes and organic pigments.

[0032] In one embodiment, the layered optical device 10 can also include nanoparticles of inorganic pigments or other inorganic colorants, for example, as a color balancing means and / or as a pigment extender. Non-limiting examples of inorganic pigments include metal pigments such as Ag, Au, Cu, Fe, Pb, Pd, and Pt; metal oxide pigments such as Al2O3, Fe2O3, Fe3O4, Cr2O3, CuO, Cu2O, In2O3, Mn2O3, PbO, PdO, SnO2, TiO2, ZnO, and ZrO2; metal halides such as AgCl, AgBr, AgClxBr1-x, and CuCl; TiC; Suitable inorganic pigments include metal carbides such as BC and BC, metal nitrides such as BN and TiN, metal arsenides such as CdAs, metal phosphides such as CdP, metal chalcogenides (sulfides, selenides, tellurides) such as AgS, CdS, HgS, PbS, FeS, MoS, and ZnS, CdSe, ZnSe, and CdTe, as well as mixed phases such as ZnSe / PbS and CdS / PbS. Additional groups of suitable inorganic pigments include non-metallic pigments, primarily carbon in the form of graphite or carbon black, non-metallic oxide pigments such as SiO, and minerals such as mica, spinels such as magnetite or copper chromium spinel, heavy spar (BaSO), or fluorite (CaF). The inorganic pigment nanoparticles can optionally be present in the composition in any suitable amount, such as from about 0.1% to about 50% by weight based on the total weight of the optical device. In one embodiment of the present invention, the inorganic pigment is employed at a lower wt % concentration than the concentration of the organic colorant 30, or is not employed at all. For example, the inorganic pigment can be employed at a concentration of 0 wt % to about 10 wt %, e.g., about 0.001 wt % to about 5 wt %, or about 0.1 wt % to about 1 wt %, based on the total weight of the optical device. In some embodiments, the inorganic pigment can have any of the D50 or D99 particle size ranges taught herein for organic colorants. In one embodiment, carbon black is not employed as the inorganic pigment.

[0033] Any one or more of the inorganic pigments described above can be included in combination with any one or more of the organic colorants described above (e.g., dyes and / or organic nanopigments) in the matrix of optical device 10. When a multi-layer stack of matrix materials is employed, one or more layers of stack 68 (FIG. 4) can include at least one organic colorant 30, optionally in combination with at least one inorganic pigment, while one or more other layers of stack 68 include only at least one organic colorant 30, only at least one inorganic pigment, or no organic or inorganic pigments. Alternatively, optical device 10 does not include an inorganic pigment (e.g., all layers of optical device 10 include at least one organic colorant 30).

[0034] As an example, inorganic pigments can be employed as internal light filters in combination with organic colorants 30, thereby protecting the organic colorants from light degradation and improving their lightfastness. Inorganic pigments generally have higher lightfastness than organic colorants. The overall lightfastness of the optical device 10 can be enhanced by including a combination of at least one organic colorant 30 and at least one inorganic pigment, with the at least one inorganic pigment functioning as an internal light filter for the host material 20. Examples of suitable inorganic pigments that can function as light filters include metal nanoparticles or other UV-reflecting or absorbing particles, indium tin oxide (ITO) particles, zinc oxide particles, and carbon black particles. The inorganic pigment can be included in the same layer as the organic colorant or in a different layer. For example, referring to FIG. 4, layer 64 can include at least one organic colorant 30, and layers 62 and 66 can include at least one inorganic pigment functioning as a light filter. At least one organic pigment 30 in layer 64 can be protected from light degradation by including light-filtering inorganic pigments in layers 62 and 66 on either side of layer 64 in the final optical device 10. As explained in more detail below, the final optical device 10 does not include substrate 26 and optional release layer 28, which are shown in FIG.

[0035] The optical device 10 can be designed to include various additives. For example, at least one additive can be selected from UV stabilizers, antioxidants, structural fillers, functional fillers, pigment extenders, surface modifiers, and coupling agents. Examples of structural fillers include inorganic nanoparticles used as mechanical tougheners and / or to enhance hardness, such as nanoparticles of various oxides, such as SiO2, ZrO2, and minerals such as kaolinite and mica. Examples of functional fillers include nanoparticles such as ZnO and TiO2, silsesquioxanes, and indium tin oxide (ITO). Examples of surface modifiers include chemically modified polyalcohols, acrylate-modified glycols, and hydroxyaminopolysiloxanes. Examples of coupling agents include organosilanes containing one or more functional groups selected from amino, epoxy, vinyl, and acrylate groups.

[0036] The role of these additives is to design and / or adjust one or more performance attributes of the optical device 10. Below is a list of some exemplary functional additives, along with the properties of the optical device they are designed to affect or improve: UV stabilizers to improve lightfastness; antioxidants to improve environmental stability and durability; structural and / or functional fillers to control hardness / brittleness, aid in manufacturing (e.g., release from the substrate and / or sizing of the final optical device 10), adjust heat transfer, and / or increase refractive index; pigment extenders to improve color and lightfastness; and coupling agents to adjust compatibility with various paint systems. In one embodiment, each additive of the at least one additive can be present in the optical device 10 in any amount sufficient to provide a desired effect, such as any of the effects for the specific additive described herein. For example, a UV stabilizer can be provided in an amount sufficient to increase lightfastness when compared to an identical optical device without the UV stabilizer. One skilled in the art would be able to determine the effective amount of each additive, which amount can vary based on the type of additive and the desired effect. The optimal amount of each additive can range, for example, from about 0.1% to about 50% by weight, for example, from about 1% to about 40% by weight, and as a further example, from about 2% to about 30% by weight, based on the mass of the optical device 10.

[0037] By appropriately selecting the chemistries of the matrix 20, colorants, and additives, as well as their ratios, the optical device 10 can be designed to have a variety of desired properties and / or attributes. Such properties and / or attributes may include, for example, hue, chromaticity, hiding power, lightfastness, flop, chemical and mechanical stability, environmental stability, optical special effects, compatibility with various paint systems or other compositions discussed herein, cost, and / or regulatory compliance. This allows a layered optical device 10, such as an optical device in flake or platelet form, to be designed with any selected organic colorant 30, as described herein, to provide a selected hue, while the optical device 10 incorporates application-specific stabilization features, such as those for enhancing the lightfastness, chemical stability, and / or thermal stability of the particular colorant 30 used. These stabilization features can be incorporated into the matrix 20 of the optical device 10. This can also allow for the use of different matrixes and / or additives for different colorants in a single final composition, such as a paint. This can also allow for improved tailoring of the matrix and additives for a given colorant in an economical and efficient manner.

[0038] Furthermore, the engineered optical device 10 of the present invention allows for increased flexibility in selecting optical and other properties. For example, flop is controlled by the colorant particle size (preferably <100 nm, low visible light scattering), flake flatness, specular properties, and planar alignment of the flakes in the coating to achieve the desired "flop" effect (e.g., the color appears darker under increasing viewing angles). On the other hand, the lightfastness and durability of a colorant, or a composition incorporating a colorant, generally increase as the colorant particle size increases; therefore, as the colorant particle size decreases, such as particle sizes below 100 nm, the lightfastness and durability decrease. The optical device 10 of the present invention can be designed to provide good flop properties by employing very small colorants 30 with low visible light scattering, while at the same time, better lightfastness and durability can be achieved by employing an optical device 10 having small colorants 30 in the color composition 50 than would be achieved by using the same colorant 30 directly in the color composition 50 without embedding it in the optical device 10.

[0039] 2, the optical device 10 can be constructed from a single free-standing layer of host material 20. The at least one organic colorant 30 can be uniformly dispersed throughout the host material 20, or can have a non-uniform distribution.

[0040] The layered geometry of optical device 10 allows for manipulation of the surface topography of the flakes. By way of example, the surfaces can be planar and optically specular. For example, as shown in FIG. 2, both major facing surfaces 40 of optical device 10 are planar. Major facing surfaces 40 can be sufficiently flat to provide specular reflection of visible and / or UV light.

[0041] Alternatively, as shown in FIG. 3, optical device 10 can include a textured surface 40 for light scattering or diffraction. For example, it is possible to control the diffusion properties of layered optical device 10 by molding one or more major surfaces 40 with a controlled degree of roughness. In one embodiment, optical device 10 has at least one, two, or more major surfaces 40 with a non-planar topography configured to diffuse light (e.g., visible or UV light) rather than provide specular reflection. In one embodiment, the non-planar topography can have a surface roughness ranging from about 0.25 μm RMS to about 2 μm RMS, for example.

[0042] In one embodiment, the non-planar topography is a surface textured with a diffraction grating, which, combined with a sufficiently high refractive index of the host material, can result in an optical device 10 that is a special effect diffractive pigment. The refractive index of the host material 20 can be higher than the refractive index of the color composition (e.g., paint) into which the optical device 10 is to be incorporated, for example, about 1.5 or higher, e.g., about 1.65 to about 2. Any suitable diffraction grating can be employed, for example, a diffraction grating having a feature distance of about 500 lines / mm to about 4000 lines / mm and an amplitude of about 50 nm to about 200 nm.

[0043] In one embodiment, the optical device 10 can include multiple adjacent layers of a matrix, as shown in FIG. 4. While FIG. 4 illustrates an example having three distinct layers 62, 64, and 66, any number of layers, such as two to ten layers, can be employed. The adjacent layers can be arranged in a stack 68. The layers can be the same or different. If the layers are different, the layer can have at least one component that is different from another layer in the stack, where the at least one component is selected from a different matrix, a different colorant, and / or a different additive. By way of example, the same or different matrix can be used for different layers in the stack 68, and a different colorant 30 can be used for each layer in the stack.

[0044] In some embodiments, all layers in stack 68 can have both major opposing surfaces 40 that are planar (i.e., none of the surfaces are configured to have a non-planar topography, such as might be formed by embossing). For example, in some embodiments, the optical device does not include an embossed layer. Alternatively, one or more layers of stack 68 can be configured to include a non-planar topography, such as a diffraction grating or any of the other non-planar topographies described herein. As shown in FIG. 3 , major opposing surfaces 40 are two opposing surfaces having a width dimension “b” that is orthogonal to a thickness dimension “a,” which generally corresponds to the thickness of the matrix layer formed on substrate 26 ( FIG. 4 ) after final processing of matrix 20 (e.g., final drying, curing, and optional embossing).

[0045] In one embodiment, optical device 10 does not include a metal layer, such as a metal reflective layer or a metal absorbing layer, as a layer in stack 68, where metal is defined to include both elemental metals and metal alloys. Reflective layers, as disclosed herein, are generally thick enough to be opaque to visible light, while absorbing layers are thin enough (e.g., transparent or translucent) for all transmission of visible light through the layer. In some embodiments, optical device 10 does not include a metal layer; instead, the metal layer is a continuous metal layer having a first major surface and an opposing second major surface, each having the same or approximately the same surface area as major surface 40 of layered optical device 10, where “approximately” is defined as a difference in surface area of 20% or less, based on the surface area of major surface 40. In one embodiment, optical device 10 does not include an opaque layer (i.e., a layer that does not transmit visible light), such as an opaque metal layer or a non-metallic layer with reflective properties. As an example, optical device 10 does not include an aluminum layer or an aluminum alloy. In embodiments where a metallic reflective layer or other opaque layer is not present, optical device 10 may optionally be transparent or translucent to visible light.

[0046] In one aspect, the color provided by optical device 10 alone is not the result of interference effects. Rather, the color provided by optical device 10 is primarily or entirely the result of selective absorption within the visible light spectrum by organic colorant 30 and any inorganic colorants employed. That said, when optical device 10 is incorporated into a color composition 50, the option of engineering a refractive index differential into color composition 50 (e.g., paint, ink, or varnish) allows the ability to provide diffractive / reflective effects, if desired, based on the difference between the refractive index of optical device 10 and the refractive index of the substrate material of the paint or other color composition 50 (after drying) in which optical device 10 is incorporated.

[0047] In one embodiment of an optical device 10 including a stack of layers 68, the refractive index of the matrix 20 alone, or the combination of the matrix and colorant 30, optional inorganic colorants, and additives, of each layer (e.g., layers 62, 64, 66) of the stack 68, is the same or substantially similar to the refractive index of adjacent layers in the stack so as not to provide significant interference color effects (e.g., no interference color effects, or no noticeable interference color effects). For example, the refractive index of the matrix alone, or the combination of the matrix and colorant 30, optional inorganic colorants, and additives, of each layer in the stack has a refractive index difference of 0.1 or less compared to other layers in the stack adjacent to that layer. In one embodiment, the refractive index of each layer in the stack is 1.65 or less, or alternatively, the refractive index of each layer in the stack is 1.65 or greater.

[0048] The optical device 10 of the present application can have any suitable size. For example, the width "b" of the optical device can range from about 0.2 μm to about 500 μm, such as from about 0.5 μm to about 100 μm, or from about 1 μm to about 50 μm. Those skilled in the art will readily appreciate that the population width of the optical device 10 can be determined as a D50 value, as is well known in the art. The optical device 10 can have a D50 of, for example, from about 1 μm to about 100 μm, such as from about 10 μm to about 30 μm. The optical device 10 can have a D50 of, for example, from about 1 μm to about 100 μm, such as from about 10 μm to about 30 μm. The population D50 of the optical device 10 can be determined using a Malvern Mastersizer 3000, available from Malvern Panalytical, headquartered in Malvern, UK. TM The thickness "a" of the optical device 10 can range from about 0.2 microns to about 10 microns, or from about 1 micron to about 5 microns.

[0049] As described herein, the optical device 10 can be in the form of a layered form factor particle, as shown, for example, in FIGS. 2 and 3. The layered form factor of the optical device 10 described herein allows for control of the thickness and aspect ratio of the optical device. In one embodiment, the matrix 20 is configured so that the optical device 10 has an aspect ratio of width "b" to thickness "a," as shown in FIG. 3. The aspect ratio b:a can range from about 2:1 to about 10,000:1, e.g., from about 5:1 to about 5000:1, or from about 10:1 to about 1000:1. In other examples, the aspect ratio can be about 1:1 or greater, e.g., about 2:1 or greater, or about 5:1 or greater, e.g., from about 1:1 to about 500:1, e.g., from about 2:1 to about 250:1, from about 2:1 to about 100:1, or from about 2:1 to about 50:1.

[0050] In one embodiment, the layered form factor and the method employed to fabricate the optical device 10 may allow for precise thickness control of the optical device 10, thereby allowing for precise color control. As an example, the population of optical devices 10 incorporated into the color composition 50 may be almost all, substantially all, or all have a uniform thickness (e.g., may vary in thickness by less than 3%, less than 2%, or less than 1%), where "almost all" refers to 75% or more of the optical devices in the population and "substantially all" refers to 90% or more of the optical devices in the population. In some embodiments, the population of optical devices 10 in the color composition are of the same hue and material (e.g., have the same organic colorant, host material, and additives). In embodiments, two or more different populations of optical devices 10 are incorporated into the color composition, each population having a different hue and / or material (e.g., different organic colorant, host material, and / or additives). Each of the different populations of optical devices 10 can be nearly all, substantially all, or all have a uniform thickness (e.g., can differ in thickness by less than 3%, less than 2%, or less than 1%). The ability to provide a relatively uniform thickness within each of one or more populations of optical devices 10 can also allow for more uniform control of aspect ratios.

[0051] The present disclosure is also directed to a method of making the optical device 10. The method includes combining at least one organic colorant 30, at least one additive, and a liquid matrix to form a coating composition. The at least one organic colorant 30 can be any of the colorants 30 described herein, such as an organic dye, an organic nanopigment, or a combination thereof. In one embodiment, the at least one organic colorant has any of the particle sizes and / or aspect ratios described herein.

[0052] 4, a coating composition is deposited on substrate 26 using a liquid coating process. The coating composition is then solidified to form a solid layer, such as any of the matrix 20 layers described herein. Optionally, additional layers of the same or different coating composition can be deposited to form a stack 68 of any of the solid layers described herein, as exemplified by layers 62, 64, and 66. Substrate 26 is released from solid layer or stack 68. In one embodiment, the method further includes separating solid layer or layer stack 68 into particles to form optical device 10 using any suitable sizing technique, as described in more detail herein below.

[0053] Any of the optical devices 10 described herein can be made by the method of the present application. In one embodiment, the method includes depositing only a single layer such that the final optical device includes only a single layer of a base material 20, the single layer including at least one colorant and at least one additive, as described herein. Alternatively, the optical device 10 can include two or more adjacent layers of a base material in a stack, such as any of the multilayer optical devices 10 described herein. Any of the base materials, colorants, and additives described herein can be employed in the method of the present application.

[0054] The method may include combining at least one colorant, at least one additive, and a liquid matrix to form a coating composition. The liquid matrix may be an aqueous-based composition or an organic solution-based composition (e.g., a composition comprising primarily an organic carrier and / or solvent) containing matrix precursors such as monomers, oligomers, and other components. Any suitable technique for forming the coating composition may be employed. The matrix components, at least one organic colorant, and at least one additive may be added to the coating composition in any suitable order. An example of a suitable technique includes forming the matrix by a sol-gel process using precursors of various metal oxides, and the at least one colorant and / or at least one additive may be added during or after the formation of the liquid matrix. As an example, the colorant may be incorporated into the matrix by dispersion or dissolution, optionally with the aid of an aqueous or organic-based processing solution, such as any of the organic or aqueous-based solvents disclosed herein. Any other suitable technique may be employed.

[0055] The coating composition can have a solids content ranging from about 0.01% to about 100%, such as from about 0.05% to about 80%, and as a further example, from about 1% to about 30%. In some embodiments, the solids content can be greater than 3%. In some embodiments, the coating composition can have a solids content ranging from about 3% to about 100%, such as from about 4% to about 50%.

[0056] In some embodiments, the at least one organic colorant and any inorganic colorant can be part of a selective light modulator system (SLMS). The SLMS can include at least one coating component other than the colorant, such as at least one coating composition component selected from a curing agent and a coating aid. The components of the SLMS can be combined with other components of the coating composition together as a combined SLMS or individually in any desired order.

[0057] A curing agent can be a compound or material that can initiate the hardening, vitrification, crosslinking, or polymerization of a host material. Non-limiting examples of curing agents include solvents, radical generators (energetic or chemical), acid generators (energetic or chemical), condensation initiators, and acid / base catalysts.

[0058] Non-limiting examples of coating aids include leveling agents, wetting agents, defoamers, cure inhibition mitigators, stain repellents, corrosion inhibitors, photosensitizers, secondary crosslinkers, infrared absorbers for infrared drying enhancement, and adhesion promoters. In one embodiment, the antioxidant may be present in the coating composition in an amount ranging from about 25 ppm to about 5 wt. %.

[0059] As described above, the coating compositions for one or more layers of optical device 10 can each independently comprise an organic or aqueous-based solvent. Non-limiting examples of solvents include acetates such as ethyl acetate, propyl acetate, and butyl acetate, acetone, water, ketones such as dimethyl ketone (DMK), methyl ethyl ketone (MEK), secbutyl methyl ketone (SBMK), terbutyl methyl ketone (TBMK), cyclopentanone, and anisole, glycols and glycol derivatives such as propylene glycol methyl ether and propylene glycol methyl ether acetate, alcohols such as isopropyl alcohol and diacetone alcohol, esters such as malonates, heterocyclic solvents such as n-methylpyrrolidone, hydrocarbons such as toluene and xylene, coalescing solvents such as glycol ethers, and mixtures thereof. In one embodiment, the solvent can be present in the coating composition in an amount ranging from about 0% to about 99.9%, such as from about 0.005% to about 99%, and as a further example, from about 0.05% to about 90%, based on the total weight of the coating composition.

[0060] In some examples, the coating composition may include at least one component selected from (i) a photoinitiator, (ii) an oxygen inhibition mitigation composition, (iii) a leveling agent, and (iv) an antifoaming agent.

[0061] The oxygen inhibition mitigation composition can be used to mitigate oxygen inhibition of free radical materials. Molecular oxygen can quench the triplet state of a photoinitiator sensitizer or scavenge free radicals, resulting in a deterioration of coating properties and / or the uncured liquid surface. The oxygen inhibition mitigation composition can reduce oxygen inhibition or improve the cure of the base material.

[0062] The oxygen inhibition mitigation composition can include one or more compounds. The oxygen inhibition mitigation composition can include at least one acrylate, such as at least one acrylate monomer and at least one acrylate oligomer. In one embodiment, the oxygen inhibition mitigation composition can include at least one acrylate monomer and two acrylate oligomers. Non-limiting examples of acrylates for use in the oxygen inhibition mitigation composition can include acrylates, methacrylates, epoxy acrylates such as modified epoxy acrylates, polyester acrylates such as acid-functional polyester acrylates, tetrafunctional polyester acrylates, modified polyester acrylates, and bio-based polyester acrylates, polyether acrylates such as amine-modified polyether acrylates containing amine-functional acrylate co-initiators and tertiary amine co-initiators, urethane acrylates such as aromatic urethane acrylates, modified aliphatic urethane acrylates, aliphatic urethane acrylates, and aliphatic allophanate-based urethane acrylates, and monomers and oligomers thereof. In one embodiment, the oxygen inhibition mitigation composition can include at least one acrylate oligomer, for example, two oligomers. The at least one acrylate oligomer can be selected from polyester acrylates and polyether acrylates, such as mercapto-modified polyester acrylates and amine-modified polyether tetraacrylates. The oxygen inhibition mitigation composition can also include at least one monomer, such as 1,6-hexanediol diacrylate. The oxygen inhibition mitigation composition can be present in the liquid coating composition in an amount ranging from about 5% to about 95%, for example, from about 10% to about 90%, and further example, from about 15% to about 85%, based on the total weight of the liquid coating composition.

[0063] In some instances, the base material may utilize a non-radical curing system, such as a cationic system. Cationic systems are less susceptible to mitigation of oxygen inhibition of free radical processes and therefore may not require an oxygen inhibition mitigation composition. As an example, the use of the monomer 3-ethyl-3-hydroxymethyloxetane does not require an oxygen inhibition mitigation composition.

[0064] In one embodiment, the coating composition of each layer of the substrate employed in the optical device 10 can independently include at least one photoinitiator, e.g., two photoinitiators, or three photoinitiators. Photoinitiators can be used for shorter wavelengths. Photoinitiators can be active at actinic wavelengths. The photoinitiators can be Type I or Type II photoinitiators. The coating composition can include only Type I photoinitiators, only Type II photoinitiators, or a combination of both Type I and Type II photoinitiators. The photoinitiator can be present in the coating composition in an amount ranging from about 0.25% to about 15%, for example, from about 0.5% to about 10%, and further example, from about 1% to about 5%, based on the total weight of the liquid coating composition.

[0065] The photoinitiator can be a phosphine oxide. Phosphine oxides can include, but are not limited to, monoacylphosphine oxides and bisacylphosphine oxides. The monoacylphosphine oxide can be diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide. The bisacylphosphine oxide can be bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. In one embodiment, at least one phosphine oxide can be present in the coating composition. For example, two phosphine oxides can be present in the composition.

[0066] A sensitizer can be present in the coating composition and can act as a sensitizer for the Type I and / or Type II photoinitiator. The sensitizer can also act as a Type II photoinitiator. In one embodiment, the sensitizer can be present in the coating composition in an amount ranging from about 0.05% to about 10%, for example, from about 0.1% to about 7%, and as a further example, from about 1% to about 5%, based on the total weight of the coating composition. The sensitizer can be a thioxanthone, such as 1-chloro-4-propoxythioxanthone.

[0067] In one embodiment, the coating composition can include a leveling agent. The leveling agent can be a polyacrylate. The leveling agent can eliminate crater rings in a layer of a base material deposited using the coating composition. The leveling agent can be present in the coating composition in an amount ranging from about 0.05% to about 10%, for example, from about 1% to about 7%, and further example, from about 2% to about 5%, based on the total weight of the coating composition.

[0068] The coating composition may also include an antifoaming agent. The antifoaming agent may reduce surface tension. The antifoaming agent may be a silicone-free liquid organic polymer. The antifoaming agent may be present in the coating composition in an amount ranging from about 0.05% to about 5%, for example, from about 0.2% to about 4%, and further for example, from about 0.4% to about 3%, based on the total weight of the coating composition.

[0069] The coating composition is deposited on the substrate 26 using a liquid coating process. The substrate 26 can have any suitable configuration and can be either flexible or rigid. In one embodiment, the substrate 26 can be made of a flexible material present in a roll configuration so that the layers of the diffractive optical device 10 are deposited on the substrate 26 as it moves from an unwind roll configuration to a rewind roll configuration, as is well known in the art. The wavy edges of the substrate 26, release layer 28, and stack 68 in FIG. 4 are intended to illustrate that the substrate and the layers deposited thereon can expand in both directions along the length of the substrate during the deposition process. The substrate 26 can be any suitable material capable of receiving multiple layers deposited during the manufacturing process. Non-limiting examples of suitable substrate materials include polymer webs such as polyethylene terephthalate (PET), glass foils, glass sheets, polymer foils, polymer sheets, metal foils, metal sheets, ceramic foils, ceramic sheets, ionic liquids, paper, silicon wafers, etc. As noted above, the substrate 26 can be made of a flexible material. In embodiments where embossing is employed to shape a layer of optical device 10, substrate 26 can comprise a material having a Tg temperature higher than the Tg of the embossed layer and / or other layers of optical device 10. In certain embodiments, the substrate comprises a heat-resistant material such as polyester, polyamide, polyvinyl chloride, or propylene. The substrate can have any suitable thickness, such as, for example, from about 6 μm to about 200 μm, and as a further example, from about 10 μm to about 50 μm.

[0070] In some embodiments, the substrate is temporary and is removed from the optical device layer as described below. For example, the coating composition can be coated onto a temporary substrate, optionally including an optional release layer 28.

[0071] The coating composition is deposited by a wet coating method. For example, the coating composition for one or more optical device layers can be coated / applied / deposited using a liquid coating process. Non-limiting examples of liquid coating processes include slot die, comma bar, knife, spray, gravure, microgravure, inkjet, curtain coating, metering rod, Mayer rod coating, flexography, offset printing, slot bead, slide bead, slot curtain, slide curtain, tension web, and reverse roll, as well as other liquid coating and printing processes that apply a liquid onto a substrate or a previously deposited layer to form a liquid layer or film that is subsequently dried and / or cured. In one embodiment, the deposition method is selected from slot die, slot bead, slide bead, slot curtain, and slide curtain.

[0072] Liquid coating processes allow for the deposition of optical device coatings at faster rates than other deposition techniques, such as vapor deposition. Furthermore, liquid coating processes allow for a wider variety of materials to be used in layers, with simpler equipment setup than vapor deposition methods. It is believed that layers formed using liquid coating processes can exhibit improved optical performance.

[0073] After deposition, the coating composition can be solidified to form a solid layer. Solidifying the coating composition can include evaporating the processing solvent and converting the liquid matrix into a solid layer by any suitable technique, such as additional drying and / or curing techniques. Curing can be employed to crosslink the polymer precursors of the matrix and can be carried out by any desired technique, including any of the techniques discussed herein.

[0074] After the wet coating composition is deposited on the substrate 26, the solvent present in the wet coating composition can be evaporated. The liquid coating process continues curing the wet coating composition, resulting in a cured, self-leveling optical device layer having a desired thickness. It is believed that the ability of the optical device layer to self-level results in a layer with reduced optical thickness variation throughout the layer. Ultimately, an article 10, such as an optical device, including a self-leveling optical device layer can exhibit increased optical accuracy. For ease of understanding, the term "wet film" refers to the wet coating composition, and "dry film" refers to the final dried / cured layer of the optical device 10 after final drying / curing. Unless otherwise specified, "coating composition" generally refers to the coating composition before drying or curing occurs.

[0075] The solvent can be evaporated from the wet film, such as before curing the wet film. In one embodiment, about 100%, such as about 99.9%, and as a further example, about 99.8%, of the solvent can be evaporated from the coating composition before curing. In further embodiments, trace amounts of solvent can be present in the cured / dried layer. In some embodiments, a wet film with a greater original weight percent of solvent can result in a dried film with a reduced film thickness H. In particular, a wet film with a high weight percent of solvent and deposited at a high wet film thickness D can result in layer 10 of the optical device with a low dry film thickness H. It is important to note that after solvent evaporation, the wet film remains liquid, thereby avoiding problems such as skinning and island formation during the subsequent curing step in the liquid coating process.

[0076] For example, the dynamic viscosity of the wet film before drying can range from about 0.5 to about 50 cP, such as from about 1 to about 45 cP, and as a further example, from about 2 to about 40 cP. The viscosity measurement temperature is 25°C, and the rheology can be measured with an Anton Paar MCR101 rheometer equipped with a solvent trap using a cone / plate with a 40 mm diameter, a 0.3° angle, and a 0.025 mm gap setting.

[0077] In some embodiments, the matrix precursor and solvent can be selected to provide a wet film exhibiting Newtonian behavior for precision coating using a liquid coating process. The wet film can exhibit Newtonian behavior at shear rates of 10,000 / s or greater. For example, the shear rate for a liquid coating process can be 1000 / s for coating speeds up to 25 m / min, 3900 / s for coating speeds up to 100 m / min, and 7900 / s for coating speeds up to 200 m / min. It is understood that the maximum shear rate occurs at very thin wet films, such as those with a thickness of 1 μm. As the thickness of the wet film increases, the shear rate is expected to decrease, for example, by 15% for a 10 μm wet film, and as a further example, by 30% for a 20 μm wet film.

[0078] Evaporation of solvent from the wet film can cause a change in viscosity behavior to pseudoplastic, which can be beneficial for achieving layers of precision optical device 10. The dynamic viscosity of the deposited coating composition after any solvent has evaporated can range from about 10 cP to about 3000 cP, such as from about 20 cP to about 2500 cP, and as a further example, from about 30 cP to about 2000 cP. If solvent is present, there can be an increase in viscosity to pseudoplastic behavior as it evaporates from the wet film. The pseudoplastic behavior can allow for self-leveling of the wet film.

[0079] In one embodiment, the method can include evaporating the solvent present in the wet film using known techniques. The time required to evaporate the solvent can depend on the speed of the web / substrate and the capacity of the dryer. In one example, the temperature of the dryer (not shown) can be less than about 120°C, such as less than about 100°C, or as a further example, less than about 80°C.

[0080] Wet films deposited using liquid coating processes can be cured using known techniques. In some embodiments, the wet film can be cured using a curing agent that utilizes at least one of ultraviolet light, visible light, infrared light, or an electron beam. Curing can proceed in an inert atmosphere or an ambient atmosphere. In some embodiments, the curing step utilizes an ultraviolet light source having a wavelength of about 395 nm. The ultraviolet light source can be applied to the wet film at a dose ranging from about 200 mJ / cm to about 1000 mJ / cm, such as from about 250 mJ / cm to about 900 mJ / cm, and further example from about 850 mJ / cm.

[0081] The wet film can be crosslinked by known techniques, non-limiting examples of which include photoinduced polymerization such as free radical polymerization, spectrally sensitized photoinduced free radical polymerization, photoinduced cationic polymerization, spectrally sensitized photoinduced cationic polymerization, and photoinduced cycloaddition, electron beam induced polymerization such as electron beam induced free radical polymerization, electron beam induced cationic polymerization, and electron beam induced cycloaddition, and thermally induced polymerization such as thermally induced cationic polymerization.

[0082] The method further includes releasing substrate 26 from the solidified optical device layer (e.g., monolayer or stack 68). The solidified layer can be released from substrate 26 by mechanical processes, such as high-velocity air impingement, scraping, or, if present, chemical solvent-based dissolution / weakening or swelling of the release layer. Optional release layer 28 (FIG. 4) can have lower adhesion to adjacent solidified optical device layers (e.g., layer 62) compared to substrate 26. In one embodiment, release layer 28 is soluble in organic solvents or water and can be partially or completely dissolved or weakened to aid in separation of the solid coating from the substrate. After release, the solid layer is recovered and prepared for sizing.

[0083] The method further includes sizing the solid layer to form an optical device. Sizing generally involves sizing in the lateral, or width, dimension. Any sizing technique, such as grinding or other methods, can be employed. As an example, sizing the coating into flakes of a desired size can be achieved by mechanical air-assisted impaction and sieving, or directed energy beam (laser) sizing, or cutting or punching the desired flake size. The aspect ratio can be relatively tightly controlled to fall within a desired range. In some embodiments, the particle size can be made monodisperse, but this can be more expensive than using techniques such as mechanical grinding, which do not provide a monodisperse particle size.

[0084] In one embodiment, optical device 10 is mechanically sized (e.g., ground, such as by mechanical air-assisted impingement, or cut) and therefore has rough and / or cut edges 42 (FIGS. 2-4) that expose an internal layer (e.g., layer 64 in FIG. 4). This distinguishes the present optical device from pigments that do not have rough or cut edges, such as pigment particles that are grown in solution to a desired particle size or pigment particles that have a layer deposited on a core particle to completely surround or encapsulate the core particle.

[0085] Prior to releasing the substrate 26 from the layers of the optical device 10, one or more surfaces of the optical device can be optionally shaped to provide a desired topography, as shown in FIG. 3 . Any suitable technique can be employed to provide the desired topography, such as embossing. In one embodiment, the optical device 10 is embossed on opposing major surfaces of the layers of the matrix 20 as shown in FIG. 3 . In a multilayer stack such as that shown in FIG. 4 , one or more surfaces of one or more layers of the stack can be embossed, for example, partially or completely. For example, a first major surface of a layer can be embossed, and a second major surface of the layer can be embossed or non-embossed. Additionally and / or alternatively, one or more surfaces of one or more layers of the stack can be non-embossed. Non-embossed surfaces and / or layers can be smooth, such as flat, due to, for example, self-smoothing of a liquid-deposited coating composition. If desired, the release layer 28 can be embossed to provide a desired topography on a first surface of the optical device, followed by deposition of the coating composition. A second surface of the optical device opposite the first surface can also be embossed to provide a desired topography on the second surface. Embossing can impart any desired pattern, such as a suitable microstructure (e.g., a diffraction grating), to the deposited layer or any of the topographical configurations described herein.

[0086] Embossing of the coating composition can occur before the substrate 20 is fully solidified, for example, after partial drying and / or partial curing of the substrate. After depositing a layer of the coating composition using a liquid coating process, time is allowed for any solvent in the layer to evaporate. Additionally, the deposited layer can be subjected to a curing step. In one embodiment, embossing can be performed before the deposited layer is fully cured. In this manner, the embossing step can utilize less pressure and / or temperature compared to embossing a fully cured layer and / or a layer applied using a vacuum deposition process.

[0087] The present disclosure is also directed to a color composition 50, such as a paint, ink, varnish, or any other composition in which pigments may be employed, comprising a liquid medium and a plurality of optical devices 10 dispersed therein. As an example, the color composition is a paint used in automobiles, aircraft, boats, residential exteriors, or other outdoor applications where lightfastness is desired.

[0088] The colored composition can be employed with any of the optical devices 10 described herein. For example, the optical devices 10 can be made of any of the same materials, such as host materials, colorants, additives, etc., and can have any of the same properties, characteristics, sizes, shapes, etc., as described herein for any of the optical devices 10.

[0089] In one embodiment, the plurality of optical devices 10 have a uniform thickness "a" from optical device to optical device in a given optical device population. Either optical devices or optical device populations having a uniform thickness as described herein can be employed. For example, the plurality of optical devices of the color composition 50 can include a population of optical devices having the same colorant, with 75% or more of the optical devices in the population having a uniform thickness from optical device to optical device. As described above herein, the average thickness variation between optical devices can be less than 5%, e.g., less than 3% or less than 1%. Multiple different optical device populations, each having a uniform thickness from optical device to optical device, can be employed in the same composition 50, as described in more detail herein.

[0090] In one embodiment, the matrix 20 of the optical device 10 can have a refractive index that is the same as or different from the refractive index of the substrate material surrounding the optical device 10 in the dry color composition 50, where "dry color composition" refers to the color composition 50 after final drying and / or curing of the color composition. As an example, an optical device can be designed with a matrix 20 having a refractive index that is higher than the refractive index of the substrate material of the dry color composition 50 to provide a desired optical effect, such as reflection, diffraction, and / or an opalescent effect. As an example, the matrix 20 can have a refractive index that is at least 0.1 greater than the refractive index of the substrate material surrounding the optical device in the dry color composition 50. [Example]

[0091] 5 and 6 show dry color compositions 50 formed into layers comprising a layered optical device 10 according to the present application. The optical device 10 of FIG. 5 comprises a single layer of an acrylate matrix having mixed therein an organic molecular yellow dye and leveling agent additive (BYK-361N available from BYK). The optical device 10 of FIG. 6 comprises a single layer of an acrylate matrix having mixed therein an organic nano-sized cyan pigment and leveling agent (BYK-361N available from BYK).

[0092] From the foregoing description, those skilled in the art will appreciate that the present teachings can be embodied in a variety of forms. Accordingly, although these teachings have been described with reference to specific embodiments and examples thereof, the true scope of the present teachings should not be so limited. Various changes and modifications can be made without departing from the scope of the teachings herein.

[0093] The scope of the present disclosure should be construed broadly. The present disclosure is intended to disclose equivalents, means, systems, and methods for achieving the devices, acts, and mechanical functions disclosed herein. For each device, article, method, means, mechanical element, or mechanism disclosed, the present disclosure is intended to encompass and teach equivalents, means, systems, and methods for implementing the many aspects, mechanisms, and devices disclosed herein. The claims of this application should likewise be construed broadly. The description of the invention in its many embodiments herein is merely exemplary in nature, and thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not considered to depart from the spirit and scope of the invention.

Claims

1. 1. An optical device, comprising: a host material comprising an optically transparent material; at least one organic colorant in said matrix; and at least one additive; Equipped with The optical device is a particle having a layered shape.

2. 10. The optical device of claim 1, wherein the base material has a first major surface and a second major surface opposite the first major surface, the first major surface and the second major surface being outermost surfaces of the optical device.

3. The optical device of claim 1 , wherein the matrix comprises one or more polymers.

4. 10. The optical device of claim 1, wherein the at least one organic colorant comprises an organic nanopigment or dye.

5. 10. The optical device of claim 1, wherein the at least one organic colorant comprises a nanopigment selected from benzimidazolone-derived pigments, diketopyrrolopyrrole (DPP) pigments, disazo condensation pigments, isoindolines, perylene pigments, and phthalocyanine pigments.

6. 10. The optical device of claim 1, wherein the at least one organic colorant comprises a dye selected from polymethine dyes, phthalocyanine dyes, porphyrin dyes, azo dyes, and anthraquinone dyes.

7. 10. The optical device of claim 1, wherein the at least one additive is selected from UV stabilizers, antioxidants, structural fillers, functional fillers, pigment extenders, surface modifiers, and binders.

8. A coating system comprising the optical device of claim 1.

9. A color composition comprising: a liquid medium; and a plurality of optical devices according to claim 1 dispersed in the liquid medium; A color composition comprising:

10. 10. The composition of claim 9, wherein the plurality of optical devices comprises a population of optical devices having the same colorant, and wherein 75% or more of the optical devices in the population have a uniform thickness from optical device to optical device.

11. 10. The composition of claim 9, wherein the composition is an ink, varnish, or paint.

12. 1. A method of making an optical device, comprising: combining at least one organic colorant, at least one additive, and a liquid matrix to form a coating composition, wherein the at least one organic colorant has a D50 particle size of less than 100 nm; depositing the coating composition onto a substrate using a liquid coating process; solidifying the base material to form a solid layer; Separating the substrate from the solid layer; and separating the solid layer into particles; A method comprising:

13. 1. An optical device, comprising: a base material in the form of a layer having a first major surface and a second major surface opposite the first major surface, the base material comprising an optically transparent material; at least one organic colorant in said matrix; and at least one additive; Equipped with An optical device, wherein the at least one organic colorant has a D50 particle size of less than 100 nm.

14. 14. The optical device of claim 13, wherein the optical device has an aspect ratio of about 2:1 to 10,000:

1.

15. 14. The optical device of claim 13, wherein the layer having a first major surface and a second major surface is a first layer, and the optical device further comprises at least one additional layer comprising a base material, the at least one additional layer and the first layer forming a stack.

16. 14. The optical device of claim 13, wherein the optical device does not include a metal layer.

17. 14. The optical device of claim 13, wherein the optical device does not include an embossed layer.

18. 14. The optical device of claim 13, wherein the host material is an organic polymer and the at least one organic colorant is a nanopigment or dye, the nanopigment or dye comprising perylene, perinone, quinacridone, quinacridonequinone, anthrapyrimidine, anthraquinone, anthanthrone, benzimidazolone, disazo condensation pigment, disazo dye, azo dye, azo pigment, quinolone, xanthene, azomethine, quinophthalone, indanthrone, phthalocyanine, triarylcarbonium, dioxazine, aminoanthraquinone, isoindoline, diketopyrrolopyrrole (DPP), thioindigo, thiazineindigo, isoindoline, isoindolinone, pyranthrone, isoviolanthrone, miyoshimethane, triarylmethane, and mixtures of two or more thereof.

19. 14. The optical device of claim 13, wherein the first major surface and the second major surface are textured for light scattering or diffraction.

20. 14. The optical device of claim 13, wherein the first major surface and the second major surface are configured to be optically specular.

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