Patent Description:
A variety of optical devices, including flakes are used as a feature of consumer applications with enhanced optical properties. In some consumer applications, a metallic effect with low to no color shift and an optically varying effect is desirable. Unfortunately, present manufacturing methods, result in optical devices that are not sufficiently chromatic and/or do not provide a sufficiently strong metallic flop. Other methods require a multilayer paint system which increases the cost of manufacturing and does not to work within the industry's standard manufacturing equipment.

<CIT> and <CIT> are useful in understanding the present invention.

According to the claimed invention, there is disclosed a sheet comprising: a reflector having a first surface, a second surface opposite the first surface, and a third surface;.

In another aspects, there are disclosed an optical device comprising portions of the sheet defined herein, and an article comprising the optical device Additional features and advantages of various embodiments will be set forth, in part, in the description that follows, and will, in part, be apparent from the description, or can be learned by the practice of various embodiments. The objectives and other advantages of various embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the description herein.

The present disclosure in its several aspects and embodiments can be more fully understood from the detailed description and the accompanying drawings, wherein:.

Throughout this specification and figures like reference numbers identify like elements.

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 an explanation of various embodiments of the present teachings. In its broad and varied embodiments, disclosed herein are articles, such as optical devices, for example, in the form of foils, sheets, and flakes; and a method of manufacturing the article. In an example, the article can be a sheet including a reflector and at least one selective light modulator layer (SLML).

In some examples, the article <NUM> can exhibit optical interference. Alternatively, in some examples, the article <NUM> can not exhibit optical interference. In an aspect, the article <NUM> can exploit interference to generate color. In another aspect, the article <NUM> can not exploit interference to generate color. For example, as described in further detail below, the appearance of color can be generated by including a selective light modulator system (SLMS), such as an additive, a selective light modulator particle (SLMP) or a selective light modulator molecule (SLMM) in the SLML.

In an aspect, as shown in <FIG>, the article <NUM> can be in a form of a sheet that can be used on an object or a substrate <NUM>. In another aspect, the article <NUM> can be in a form of a foil or flake. In an aspect, an optical device can include portions of a sheet. In another aspect, an article <NUM> can include an optical device and a liquid medium. In another aspect, the article <NUM> is an optical device in the form of a flake, for example having <NUM> to <NUM> in thickness and <NUM> to <NUM> in size. The article <NUM> can be a color shifting colorant, or can be used as a security feature for currency. Some attributes common to use of the article <NUM> can include high chromaticity (or strong color), color change with respect to viewing angle (also known as goniochromaticity or iridescence), and flop (a specular and metallic appearance that varies in lightness, hue, or chromaticity as the viewing angle varies). Additionally, the article <NUM> can be metallic in color and can not exploit interference to generate color.

<FIG> illustrate a sheet including a reflector <NUM> having a first surface, a second surface opposite the first surface; and a third surface; a first selective light modulator layer <NUM> external to of the first surface of the reflector; and a second selective light modulator layer <NUM>' external to of the second surface of the reflector; wherein the third surface (the left and/or right side of reflector <NUM>) of the reflector is open. Although <FIG> illustrate an article <NUM>, such as an optical device, in the form of a sheet, the article <NUM>, such as an optical device can also be in a form of a flake, and/or a foil, according to various examples of the present disclosure. Although, <FIG> illustrate specific layers in specific orders, one of ordinary skill in the art would appreciate that the article <NUM> can include any number of layers in any order. Additionally, the composition of any particular layer can be the same or different from the composition of any other layer.

The article <NUM>, such as an optical device in the form of a sheet, flake, or foil, can include at least one dielectric layer, such as a first SLML <NUM>, a second SLML <NUM>', a third SLML <NUM>", a fourth SLML <NUM>‴, and etc. If more than one SLML <NUM>, <NUM>' is present in an optical device, each SLML can be independent in terms of their respective compositions and physical properties. For example, a first SLML <NUM> can have a composition with a first refractive index, but a second SLML <NUM>' in the same optical device can have a different composition with a different refractive index. As another example, a first SLML <NUM> can have a composition at a first thickness, but the second SLML <NUM>' can have the same composition at a second thickness different from the first thickness. Additionally or alternatively, the article <NUM> in the form of a flake, sheet, or foil can also include a hard coat or protective layer on the surfaces of SLML <NUM> and/or SLML <NUM>'. In some examples, these layers (hard coat or protective layer) do not require optical qualities.

As shown in <FIG>, at least two surfaces/sides of reflector <NUM>, for example, the right and left surface/side as shown, can be free of SLMLs <NUM>, <NUM>'. In an aspect, if the article <NUM> is in the form of a flake or foil, then reflector <NUM> can include more than the four surfaces exemplified in <FIG>. In those instances, for example, one, two, three, four, or five surfaces of reflector <NUM> can be free of SLMLs <NUM>. In some examples, one, two, three, four, or five surfaces of reflector <NUM>, and therefore article <NUM>, can be open to the air. In an example, open sides, i.e., surfaces of the reflector that do not contain an external SLML, can be an advantage for flop.

Reflector <NUM> can be a wideband reflector, e.g., spectral and Lambertian reflector (e.g., white TiO<NUM>). Reflector <NUM> can be a metal, non-metal, or metal alloy. In one example, the materials for the at least one reflector <NUM> can include any materials that have reflective characteristics in the desired spectral range. For example, any material with a reflectance ranging from <NUM>% to <NUM>% in the desired spectral range. An example of a reflective material can be aluminum, which has good reflectance characteristics, is inexpensive, and is easy to form into or deposit as a thin layer. Other reflective materials can also be used in place of aluminum. For example, copper, silver, gold, platinum, palladium, nickel, cobalt, niobium, chromium, tin, and combinations or alloys of these or other metals can be used as reflective materials. In an aspect, the material for the at least one reflector <NUM> can be a white or light colored metal. In other examples, reflector <NUM> can include, but is not limited to, the transition and lanthanide metals and combinations thereof; as well as metal carbides, metal oxides, metal nitrides, metal sulfides, a combination thereof, or mixtures of metals and one or more of these materials.

The thickness of the at least one reflector <NUM> can range from about <NUM> to about <NUM>, although this range should not be taken as restrictive. For example, the lower thickness limit can be selected so that reflector <NUM> provides a maximum transmittance of <NUM>. Additionally or alternatively, for a reflector <NUM> including aluminum the optical density (OD) can be from about <NUM> to about <NUM> at a wavelength of about <NUM>.

In order to obtain a sufficient optical density and/or achieve a desired effect, a higher or lower minimum thicknesses can be required depending of the composition of reflector <NUM>. In some examples, the upper limit can be about <NUM>, about <NUM>, about <NUM>, about1500 nm, about <NUM>, and/or about <NUM>. In one aspect, the thickness of the at least one reflector <NUM> can range from about <NUM> to about <NUM> for example, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, such as from about <NUM> to about <NUM> or from about <NUM> to about <NUM>.

The article <NUM>, for example, in the form of a sheet, of <FIG> can include a first selective light modulator layer (SLML) <NUM> and a second selective light modulator layer <NUM>'. The SLML is a physical layer comprising a plurality of optical functions aiming at modulating (absorbing and or emitting) light intensity in different, selected regions of spectrum of electromagnetic radiation with wavelengths ranging from about <NUM> to about <NUM>.

SLMLs <NUM>, <NUM>' (and/or the materials within the SLMLs <NUM>, <NUM>') can selectively modulate light. For example, an SLML can control the amount of transmission in specific wavelengths. In some examples, the SLML can selectively absorb specific wavelengths of energy (e.g., in the visible and/or non-visible ranges). For example, the SLML <NUM>, <NUM>' can be a "colored layer" and/or a "wavelength selective absorbing layer. " In some examples, the specific wavelengths absorbed can cause the article <NUM>, for example, in the form of a flake, to appear a specific color. For example, the SLML <NUM>, <NUM>' can appear red to the human eye (e.g., the SLML can absorb wavelengths of light below approximately <NUM> and thus reflect or transmit wavelengths of energy that appear red). This can be accomplished by adding SLMPs that are colorants to a host material, such as a dielectric material, including but not limited to a polymer. For example, in some instances, the SLML can be a colored plastic.

In some examples, some or all of the specific wavelengths absorbed can be in the visible range (e.g., the SLML can be absorbing throughout the visible, but transparent in the infrared). The resulting article <NUM>, for example in the form of a flake, would appear black, but reflect light in the infrared. In some examples described above, the wavelengths absorbed (and/or the specific visible color) of the article <NUM> and/or SLML <NUM>, <NUM>' can depend, at least in part, on the thickness of the SLML <NUM>, <NUM>'. Additionally or alternatively, the wavelengths of energy absorbed by the SLML <NUM>, <NUM>' (and/or the color in which these layers and/or the flake appears) can depend in part on the addition of certain aspects to the SLML. In addition to absorbing certain wavelengths of energy, the SLML <NUM>, <NUM>' can achieve at least one of bolstering the reflector <NUM> against degradation; enabling release from a substrate; enabling sizing; providing some resistance to environmental degradation, such as oxidation of aluminum or other metals and materials used in the reflector <NUM>; and high performance in transmission, reflection, and absorption of light based upon the composition and thickness of the SLML <NUM>, <NUM>'.

In some examples, in addition to or as an alternative to the SLMLs <NUM>, <NUM>' selectively absorbing specific wavelengths of energy and/or wavelengths of visible light, the SLMLs <NUM>, <NUM>' of the article <NUM>, for example in the form of a sheet, can control the refractive index and/or the SLMLs <NUM>, <NUM>' can include SLMPs that can control refractive index. SLMPs that can control the refractive index of the SLML <NUM>, <NUM>' can be included with the host material in addition to or as an alternative to an absorption controlling SLMPs (e.g., colorants). In some examples, the host material can be combined with both absorption controlling SLMPs and refractive index SLMPs in the SLMLs <NUM>, <NUM>'. In some examples, the same SLMP can control both absorption and refractive index.

The performance of the SLML <NUM>, <NUM>' can be determined based upon the selection of materials present in the SLML14, <NUM>'. In an aspect, the SLML <NUM>, <NUM>' can improve at least one of the following properties: flake handling, corrosion, alignment, and environmental performance of any other layers within article <NUM>, e.g., the reflector <NUM>.

The first and second SLML <NUM>, <NUM>' can each independently comprise a host material alone, or a host material combined with a selective light modulator system (SLMS). In an aspect, at least one of the first SLML <NUM> and the second SLML <NUM>' includes a host material. In another aspect, at least one of the first SLML <NUM> and the second SLML <NUM>' includes a host material and a SLMS. The SLMS can include a selective light modulator molecule (SLMM), a selective light modulator particle (SLMP), an additive, or combinations thereof.

The composition of the SLML <NUM>, <NUM>' can have a solids content ranging from about <NUM>% to about <NUM>%, for example from about <NUM>% to about <NUM>%, and as a further example from about <NUM>% to about <NUM>%. In some aspects, the solids content can be greater than <NUM>%. In some aspects, the composition of the SLMLs <NUM>, <NUM>' can have a solids content ranging from about <NUM>% to about <NUM>%, for example from about <NUM>% to <NUM>%.

The host material of each of the first and/or second SLMLs <NUM>, <NUM>' can independently be a film forming material applied as a coating liquid and serving optical and structural purposes. The host material can be used as a host (matrix) for introducing, if necessary, a guest system, such as the selective light modulator system (SLMS), for providing additional light modulator properties to the article <NUM>.

The host material can be a dielectric material. Additionally or alternatively, the host material can be at least one of an organic polymer, an inorganic polymer, and a composite material. Non-limiting examples of the organic polymer include thermoplastics, such as polyesters, polyolefins, polycarbonates, polyamides, polyimides, polyurethanes, acrylics, acrylates, polyvinylesters, polyethers, polythiols, silicones, fluorocarbons, and various co-polymers thereof; thermosets, such as epoxies, polyurethanes, acrylates, melamine formaldehyde, urea formaldehyde, and phenol formaldehyde; and energy curable materials, such as acrylates, epoxies, vinyls, vinyl esters, styrenes, and silanes. Non-limiting examples of inorganic polymers includes silanes, siloxanes, titanates, zirconates, aluminates, silicates, phosphazanes, polyborazylenes, and polythiazyls.

Each of the first and second SLMLs <NUM>, <NUM>' can include from about <NUM>% to about <NUM>% by weight of a host material. In an aspect, the host material can be present in the SLML in an amount ranging from about <NUM>% to about <NUM>% by weight, for example from about <NUM>% to about <NUM>%, and as a further example from about <NUM>% to about <NUM>% by weight of the SLML.

The SLMS, for use in the SLMLs <NUM>, <NUM>' with the host material, can each independently comprise selective light modulator particles (SLMP). The SLMS can also comprise other materials. The SLMS can provide modulation of the amplitude of electromagnetic radiation (by absorption, reflectance, fluorescence etc.) in a selective region or the entire spectral range of interest (<NUM> to <NUM>).

The first and second SLMLs <NUM>, <NUM>' can each independently include in an SLMS a SLMP. The SLMP can be a particle combined with the host material to selectively control light modulation The SLMP include: quantum dots, nanoparticles (selectively reflecting and/or absorbing), micelles. The nanoparticles can include, but are not limited to organic and metalorganic materials having a high value of refractive index (n > <NUM> at wavelength of about <NUM>); metal oxides, such as TiO<NUM>, ZrO<NUM>, In<NUM>O<NUM>, In<NUM>O<NUM>-SnO, SnO<NUM>, FexOy (wherein x and y are each independently integers greater than <NUM>), and WOs; metal sulfides, such as ZnS, and CuxSy (wherein x and y are each independently integers greater than <NUM>); chalcogenides, quantum dots, metal nanoparticles; carbonates; fluorides; and mixtures thereof.

The SLMS can include selective light modulator molecules (SLMM) including organic dyes, inorganic dyes, micelles.

In some aspects, SLMS of each of the first and second SLMLs <NUM>, <NUM>' can include at least one additive, such as a curing agent, and a coating aid.

The curing agent can be a compound or material that can initiate hardening, vitrification, crosslinking, or polymerizing of the host material. Non-limiting examples of a curing agent include solvents, radical generators (by energy or chemical), acid generators (by energy or chemical), condensation initiators, and acid/base catalysts.

The levelling agent may be a coating aid. Non-limiting examples of the coating aid include wetting agents, defoamers, adhesion promoters, antioxidants, UV stabilizers, curing inhibition mitigating agents, antifouling agents, corrosion inhibitors, photosensitizers, secondary crosslinkers, and infrared absorbers for enhanced infrared drying. In an aspect, the antioxidant can be present in the composition of the SLML <NUM>, <NUM>' in an amount ranging from about <NUM> ppm to about <NUM>% by weight.

The first and second SLMLs <NUM>, <NUM>' can each independently comprise a solvent. Non-limiting examples of solvents can include acetates, such as ethyl acetate, propyl acetate, and butyl acetate; acetone; water; ketones, such as dimethyl ketone (DMK), methylethyl ketone (MEK), secbutyl methyl ketone (SBMK), ter-butyl methyl ketone (TBMK), cyclopenthanon, and anisole; glycol 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-methyl pyrrolidone; hydrocarbons, such as toluene, and xylene; coalescing solvents, such as glycol ethers; and mixtures thereof. In an aspect, the solvent can be present in each of the first and second SLML <NUM>, <NUM>' in an amount ranging from about <NUM>% to about <NUM>%, for example from about <NUM>% to about <NUM>%, and as a further example from about <NUM>% to about <NUM>% by weight relative to the total weight of the SLML <NUM>, <NUM>'.

In some examples, the first and second SLML <NUM>, <NUM>' can each independently include a composition having at least one of (i) a photoinitiator, (ii) an oxygen inhibition mitigation composition, and (iii) a defoamer.

The oxygen inhibition mitigation composition can be used to mitigate the oxygen inhibition of the free radical material. The molecular oxygen can quench the triplet state of a photoinitiator sensitizer or it can scavenge the free radicals resulting in reduced coating properties and/or uncured liquid surfaces. The oxygen inhibition mitigation composition can reduce the oxygen inhibition or can improve the cure of any SLML <NUM>, <NUM>'.

The oxygen inhibition composition can comprise more than one compound. The oxygen inhibition mitigation composition can comprise at least one acrylate, for example at least one acrylate monomer and at least one acrylate oligomer. In an aspect, the oxygen inhibition mitigation composition can comprise at least one acrylate monomer and two acrylate oligomers. Non-limiting examples of an acrylate for use in the oxygen inhibition mitigation composition can include acrylates; methacrylates; epoxy acrylates, such as modified epoxy acrylate; polyester acrylates, such as acid functional polyester acrylates, tetra functional polyester acrylates, modified polyester acrylates, and bio-sourced polyester acrylates; polyether acrylates, such as amine modified polyether acrylates including amine functional acrylate co-initiators and tertiary amine co-initiators; urethane acrylates, such aromatic urethane acrylates, modified aliphatic urethane acrylates, aliphatic urethane acrylates, and aliphatic allophanate based urethane acrylates; and monomers and oligomers thereof. In an aspect, the oxygen inhibition mitigation composition can include at least one acrylate oligomer, such as two oligomers. The at least one acrylate oligomer can be selected/chosen from a polyester acrylate and a polyether acrylate, such as a mercapto modified polyester acrylate and an amine modified polyether tetraacrylate. The oxygen inhibition mitigation composition can also include at least one monomer, such as <NUM>,<NUM>-hexanediol diacrylate. The oxygen inhibition mitigation composition can be present in the first and/or second SLML <NUM>, <NUM>' in an amount ranging from about <NUM>% to about <NUM>%, for example from about <NUM>% to about <NUM>%, and as a further example from about <NUM>% to about <NUM>% by weight relative to the total weight of the SLML <NUM>, <NUM>'.

In some examples, the host material of the SLML <NUM>, <NUM>' can use a non-radical cure system such as a cationic system. Cationic systems are less susceptible to the mitigation of the oxygen inhibition of the free radical process, and thus may not require an oxygen inhibition mitigation composition. In an example, the use of the monomer <NUM>-Ethyl-<NUM>-hydroxymethyloxetane does not require an oxygen mitigation composition.

In an aspect, the first and second SLML <NUM>, <NUM>' can each independently include at least one photoinitiator, such as two photoinitiators, or three photoinitiators. The photoinitiator can be used for shorter wavelengths. The photoinitiator can be active for actinic wavelength. The photoinitiator can be a Type <NUM> photoinitiator or a Type II photoinitiator. The SLML <NUM>, <NUM>' 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 composition of the SLML <NUM>, <NUM>' in an amount ranging from about <NUM>% to about <NUM>%, for example from about <NUM>% to about <NUM>%, and as a further example from about <NUM>% to about <NUM>% by weight relative to the total weight of the composition of the SLML <NUM>, <NUM>'.

The photoinitiator can be a phosphineoxide. The phosphineoxide can include, but is not limited to, a monoacyl phosphineoxide and a bis acyl phosphine oxide. The mono acyl phosphine oxide can be a diphenyl (<NUM>,<NUM>,<NUM>- trimethylbenzoyl)phosphineoxide. The bis acyl phosphine oxide can be a bis (<NUM>,<NUM>,<NUM>-trimethylbenzoyl)phenylphosphineoxide. In an aspect, at least one phosphineoxide can be present in the composition of the SLML <NUM>, <NUM>'. For example, two phosphineoxides can be present in the composition of the SLML <NUM>, <NUM>'.

A sensitizer can be present in the composition of the SLML <NUM>, <NUM>' and can act as a sensitizer for Type <NUM> and/or a Type II photoinitiators. The sensitizer can also act as a Type II photoinitiator. In an aspect, the sensitizer can be present in the composition of the SLML <NUM>, <NUM>' in an amount ranging from about <NUM>% to about <NUM>%, for example from about <NUM>% to about <NUM>%, and as a further example from about <NUM>% to about <NUM>% by weight relative to the total weight of the composition of the SLML <NUM>, <NUM>'. The sensitizer can be a thioxanthone, such as <NUM>-chloro-<NUM>-propoxythioxanthone.

At least one of the SLML <NUM>, <NUM>' include a levelling agent. In an aspect, the SLML <NUM>, <NUM>' can both include a leveling agent. The leveling agent can be a polyacrylate. The leveling agent can eliminate cratering of the composition of the SLML <NUM>, <NUM>'. The leveling agent can be present in the composition of the SLML <NUM>, <NUM>' in an amount ranging from about <NUM>% to about <NUM>%, for example from about <NUM>% to about <NUM>%, and as a further example from about <NUM>% to about <NUM>% by weight relative to the total weight of the composition of the SLML <NUM>, <NUM>'.

The SLML <NUM>, <NUM>' can also include a defoamer. The defoamer can reduce surface tension. The defoamer can be a silicone free liquid organic polymer. The defoamer can be present in the composition of the SLML <NUM>, <NUM>' in an amount ranging from about <NUM>% to about <NUM>%, for example from about <NUM>% to about <NUM>%, and as a further example from about <NUM>% to about <NUM>% by weight relative to the total weight of the composition of the SLML <NUM>, <NUM>'.

The first and second SLML <NUM>, <NUM>' can each independently have a refractive index of greater or less than about <NUM>. For example, each SLML <NUM>, <NUM>' can have a refractive index of approximately <NUM>. The refractive index of each SLML <NUM>, <NUM>' can be selected to provide a degree of color travel required wherein color travel can be defined as the change in hue angle measured in L*a*b* color space with the viewing angle. In some examples, each SLMLs <NUM>, <NUM>' can include a refractive index in a range of from about <NUM> to about <NUM>, about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In some examples, the refractive index of each SLMLs <NUM>, and <NUM>' can be less than about <NUM>, less than about <NUM>, or less than about <NUM>. In some examples, SLML <NUM> and SLML <NUM>' can have substantially equal refractive indexes or different refractive indexes one from the other.

The first and second SLML <NUM>, <NUM>' can each independently have a thickness ranging from about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM>, to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>. In an aspect, the article <NUM>, such as an optical device, can have an aspect ratio of <NUM>:<NUM> to <NUM>:<NUM> thickness to width.

One of the benefits of the articles <NUM> described herein, however, is that, in some examples, the optical effects appear relatively insensitive to thickness variations. Thus, in some aspects, each SLML <NUM>, <NUM>' can independently have a variation in optical thickness of less than about <NUM>%. In an aspect, each SLML <NUM>, <NUM>' can independently include an optical thickness variation of less than about <NUM>% across the layer. In an aspect, each SLML <NUM>, <NUM>' can independently have less than about <NUM>% variation in optical thickness across the layer having a thickness of about <NUM>.

In an aspect, the article <NUM>, such as an optical device in the form of a flake, foil or sheet, can also include a substrate <NUM> and a release layer <NUM> as shown in <FIG>. In an aspect, the release layer <NUM> can be disposed between the substrate <NUM> and the first SLML <NUM>.

The article <NUM>, such as optical devices, described herein can be made in any way. For example, a sheet (e.g., article <NUM> of <FIG>) can be made and then divided, broken, ground, etc. into smaller pieces forming an optical device. In some examples, the sheet (e.g., article <NUM> of <FIG>) can be created by a liquid coating process, including, but not limited the processes described below and/or with respect to <FIG>.

There is disclosed a method for manufacturing an article <NUM>, for example in the form of a sheet, flake, or foil, as described herein. The method can comprise depositing on a substrate a first SLML; depositing on the first SLML at least one reflector; and depositing on the at least one reflector a second SLML; wherein at least one of the first SLML and the second SLML is deposited using a liquid coating process.

With respect to the aspects shown in <FIG>, article <NUM>, such as an optical device, in the form of a flake, sheet, or foil, can be created by depositing the first SLML <NUM> on a substrate <NUM>. The substrate <NUM> can comprise a release layer <NUM>. In an aspect, as shown in <FIG>, the method can include depositing on the substrate <NUM>, having release layer <NUM>, the first SLML <NUM>, and depositing on the first SLML <NUM> at least one reflector <NUM>. The method further includes depositing on the at least one reflector <NUM>, a second SLML <NUM>'. In some examples, the at least one reflector <NUM> can be applied to the respective layers by any known conventional deposition process, such as physical vapor deposition, chemical vapor deposition, thin-film deposition, atomic layer deposition, etc., including modified techniques such as plasma enhanced and fluidized bed.

The substrate <NUM> can be made of a flexible material. The substrate <NUM> can be any suitable material that can receive the deposited layers. Non-limiting examples of suitable substrate materials include polymer web, such as polyethylene terephthalate (PET), glass foil, glass sheets, polymeric foils, polymeric sheets, metal foils, metal sheets, ceramic foils, ceramic sheets, ionic liquid, paper, silicon wafers, etc. The substrate <NUM> can vary in thickness, but can range for example from about <NUM> to about <NUM>, and as a further example from about <NUM> to about <NUM>.

The first SLML <NUM> can be deposited on the substrate <NUM> by a liquid coating process, such as a slot die process. Once the first SLML <NUM> has been deposited and cured, the at least one reflector <NUM> can be deposited on the first SLML <NUM> using any conventional deposition processes described above. After the at least one reflector <NUM> has been deposited on the first SLML <NUM>, the second SLML <NUM>' can be deposited on the at least one reflector <NUM> via a liquid coating apparatus, such as a slot die apparatus. The liquid coating process includes, but is not limited to: slot-bead, slide bead, slot curtain, slide curtain, in single and multilayer coating, tensioned web slot, gravure, roll coating, and other liquid coating and printing processes that apply a liquid on to a substrate to form a liquid layer or film that is subsequently dried and/or cured to the final SLML layer.

The substrate <NUM> can then be released from the deposited layers to create the article <NUM>, for example as shown in <FIG>. In an aspect, the substrate <NUM> can be cooled to embrittle the associated release layer <NUM>. In another aspect, the release layer <NUM> could be embrittled for example by heating and/or curing with photonic or e-beam energy, to increase the degree of cross-linking, which would enable stripping. The deposited layers can then be stripped mechanically, such as sharp bending or brushing of the surface. The released and stripped layers can be sized into article <NUM>, such as an optical device in the form of a flake, foil, or sheet, using known techniques.

In another aspect, the deposited layers can be transferred from the substrate <NUM> to another surface. The deposited layers can be punched or cut to produce large flakes with well-defined sizes and shapes.

As stated above, each of the first and second SLML <NUM>, <NUM>' can be deposited by a liquid coating process, such as a slot die process. However, it was previously believed that liquid coating processes, such as a slot die process, could not operate stably at optical thicknesses, such as from about <NUM> to about <NUM>. In particular thin, wet films have commonly formed islands of thick areas where solids have been wicked away from the surrounding thin areas by capillary forces as solvents evaporate. This reticulated appearance is not compatible with optical coatings as the variable thickness can result in a wide range of optical path lengths, such as a side range of colors resulting in a speckled/textured appearance, as well as reduced color uniformity of the optical coating and low chromaticity.

In an aspect of the present disclosure, the SLML <NUM>, <NUM>' can be formed using a liquid coating process, such as a slot die process. In an aspect, the liquid coating process includes, but is not limited to: slot-bead, slide bead, slot curtain, slide curtain, in single and multilayer coating, tensioned web slot, gravure, roll coating, and other liquid coating and printing processes that apply a liquid on to a substrate to form a liquid layer or film that is subsequently dried and/or cured to the final SLML layer. The liquid coating process can allow for the transfer of the composition of the SLML <NUM>, <NUM>' at a faster rate as compared to other deposition techniques, such as vapor deposition.

Additionally, the liquid coating process can allow for a wider variety of materials to be used in the SLML <NUM>, <NUM>' with a simple equipment set up. It is believed that the SLML <NUM>, <NUM>' formed using the disclosed liquid coating process can exhibit improved optical performance.

<FIG> illustrates the formation of the SLML <NUM>, <NUM>' using a liquid coating process. The composition of the SLML (a liquid coating composition) can be inserted into a slot die <NUM> and deposited on a substrate <NUM> resulting in a wet film. With reference to the processes disclosed above, the substrate <NUM> can include the substrate <NUM>, with or without a release layer <NUM>; the substrate <NUM> can include the substrate <NUM>, with or without a release layer <NUM>, a first SLML <NUM>, and the at least one reflector <NUM>; or the substrate <NUM> can include any combination of substrate <NUM>, release layer <NUM>, and deposited layers. The distance from the bottom of the slot die <NUM> to the substrate <NUM> is the slot gap G. As can be seen in <FIG>, the liquid coating composition can be deposited at a wet film thickness D that is greater than a dry film thickness H. After the wet film of the SLML <NUM>, <NUM>' has been deposited on the substrate <NUM>, any solvent present in the wet film of the SLML <NUM>, <NUM>' can be evaporated. The liquid coating process continues with curing of the wet film of the SLML <NUM>, <NUM>' to result in a cured, self-leveled SLML <NUM>, <NUM>' having the correct optical thickness H (ranging from about <NUM> to about <NUM>). It is believed that the ability of the SLML <NUM>, <NUM>' to self-level results in a layer having a reduced optical thickness variation across the layer. Ultimately, an article <NUM>, such as an optical device, comprising the self-leveled SLML <NUM>, <NUM>' can exhibit increased optical precision. For ease of understanding, the terms "wet film" and "dry film" will be used to refer to the composition at various stages of the liquid coating process that results in the SLML <NUM>, <NUM>'.

The liquid coating process can comprise adjusting at least one of a coating speed and a slot gap G to achieve a wet film with a predetermined thickness D. The SLML <NUM>, <NUM>' can be deposited having a wet film thickness D ranging from about <NUM> to about <NUM>, for example from about <NUM> to about <NUM>. The SLML <NUM>,<NUM>' formed with a wet film thickness D in the disclosed range can result in a stable SLML layer, such as a dielectric layer, i.e., without breaks or defects such as ribbing or streaks. In an aspect, the wet film can have a thickness of about <NUM> for a stable wet film using a slot die bead mode with a coating speed up to about <NUM>/min. In another aspect, the wet film can have a thickness of about <NUM>-<NUM> for a stable wet film using a slot die curtain mode with a coating speed up to about <NUM>/min.

The liquid coating process can include a ratio of slot gap G to wet film thickness D of about <NUM> to about <NUM> at speeds from about <NUM> to about <NUM>/min. In an aspect, the ratio is about <NUM> at a coating speed of about <NUM>/min. In an aspect, the ratio can be about <NUM> at a coating speed of about <NUM>/min. The liquid coating process can have a slot gap G ranging from about <NUM> to about <NUM>. A smaller slot gap G can allow for a reduced wet film thickness. In slot-bead mode higher coating speeds can be achieved with a wet film thickness greater than <NUM>.

The liquid coating process can have a coating speed ranging from about <NUM> to about <NUM>/min, for example from about <NUM>/min to about <NUM>/min, for example from about <NUM>/min to about <NUM>/min, and as a further example from about <NUM>/min to about <NUM>/min. In an aspect, the coating speed is greater than about <NUM>/min, and in a further example is greater than about <NUM>/min.

In an aspect, the coating speed for a bead mode liquid coating process can range from about <NUM>/min to about <NUM>/min, and for example from about <NUM> to about <NUM>/min. In another aspect, the coating speed for a curtain mode liquid coating process can range from about <NUM>/min to about <NUM>/min, and for example from about <NUM>/min to about <NUM>/min.

As shown in <FIG> the solvent can be evaporated from the wet film, such as before the wet film is cured. In an aspect, about <NUM>%, for example about <NUM>%, and as a further example about <NUM>% of the solvent can be evaporated from the composition of the SLML <NUM>, <NUM>', prior to curing of the SLML <NUM>, <NUM>'. In a further aspect, trace amounts of solvent can be present in a cured/dry SLML <NUM>, <NUM>'. In an aspect, a wet film having a greater original weight percent of solvent can result in a dry film having a reduced film thickness H. In particular, a wet film having a high weight percent of solvent and being deposited at a high wet film thickness D can result in a SLML <NUM>, <NUM>' having a low dry film thickness H. It is important to note, that after evaporation of the solvent, the wet film remains a liquid thereby avoiding problems such as skinning, and island formation during the subsequent curing steps in the liquid coating process.

The dynamic viscosity of the wet film can range from about <NUM> to about <NUM> cP, for example from about <NUM> to about <NUM> cP, and as a further example from about <NUM> to about <NUM> cP. The viscosity measurement temperature is <NUM>, the rheology was measured with an Anton Paar MCR <NUM> rheometer equipped with a solvent trap using a cone/plate <NUM> diameter with <NUM>° angle at a gap setting of <NUM>.

In an aspect, the composition of the SLML <NUM>, <NUM>' and the solvent can be selected so that the wet film exhibits Newtonian behavior for precision coating of the SLMLs using the liquid coating process. The wet film can exhibit Newtonian behavior shear rates up to <NUM>,<NUM>-<NUM> and higher. In an aspect, the shear rate for the liquid coating process can be <NUM>-<NUM> for a coating speed up to <NUM>/min, for example <NUM>-<NUM> for a coating speed up to <NUM>/min, and as a further example <NUM>-<NUM> for a coating speed up to <NUM>/min. It will be understood that a maximum shear rate can occur on a very thin wet film, such as <NUM> thick.

As the wet film thickness is increased, the shear rate can be expected to decrease, for example decrease <NUM>% for a <NUM> wet film, and as a further example decrease <NUM>% for a <NUM> wet film.

The evaporation of the solvent from the wet film can cause a change in viscosity behavior to pseudoplastic, which can be beneficial to achieve a precision SLML. The dynamic viscosity of the deposited first and second SLML <NUM>, <NUM>', after any solvent has been evaporated, can range from about <NUM> cP to about <NUM> cP, for example from about <NUM> cP to about 2500cP, and as a further example from about <NUM> cP to about <NUM> cP. When evaporating the solvent, if present, from the wet film there can be an increase in viscosity to the pseudoplastic behavior. The pseudoplastic behavior can allow for self-leveling of the wet film.

In an aspect, the method can include evaporating the solvent present in the wet film using known techniques. The amount of time required to evaporate the solvent can be dependent upon the speed of the web/substrate and the dryer capacity. In an aspect, the temperature of the dryer (not shown) can be less than about <NUM>° C, for example less than about <NUM>° C, and as a further example less than about <NUM>° C.

The wet film deposited using a liquid coating process can be cured using known techniques. In an aspect, the wet film can be cured using a curing agent utilizing at least one of a ultraviolet light, visible light, infrared, or electron beam. Curing can proceed in an inert or ambient atmosphere. In an aspect, the curing step utilizes an ultraviolet light source having a wavelength of about <NUM>. The ultraviolet light source can be applied to the wet film at a dose ranging from about <NUM> mJ/cm<NUM> to about <NUM> mJ/cm<NUM>, for example ranging from about <NUM> mJ/cm<NUM> to about <NUM> mJ/cm<NUM>, and as a further example from about mJ/cm<NUM> to about <NUM> mJ/cm<NUM>.

The wet film can crosslink by known techniques. Non-limiting examples 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.

A SLML <NUM>, <NUM>' formed using the liquid coating process can exhibit improved optical performance, i.e., be a precision SLML. In some examples, a precision SLML <NUM>, <NUM>' can be understood to mean a SLML having less than about <NUM>% optical thickness variation, about <NUM>% optical thickness variation, or about <NUM>% optical thickness variation across the layer.

In an aspect, the liquid coating process can include adjusting at least one of speed from about <NUM> to about <NUM>/min and a coating gap from about <NUM> to about <NUM> to deposit a wet film from about <NUM> to <NUM> of the selective light modulator layer with a predetermined thickness from about <NUM> to about <NUM>. In a further aspect, the process can include a speed of <NUM>/min, a <NUM> gap, <NUM> wet film, dry film thickness <NUM>.

In an example, the SLML includes a alicyclic epoxy resin host using a solvent dye as the SLMM, the reflector includes aluminum.

In an example, the SLML includes a alicyclic epoxy resin host using a Diketopyrrolopyrrole insoluble red dye as the SLMP, the reflector includes aluminum.

In an example, the SLML includes an acrylate oligomer resin host using white pigment (Titania) as the SLMP.

In an example, the SLML includes an acrylate oligomer resin host using black IR transparent pigment as the SLML, the reflector includes aluminum.

A method for manufacturing a sheet comprising: depositing on a substrate a first selective light modulator layer; depositing on the first selective light modulator layer at least one reflector; and depositing on the at least one reflector a second selective light modulator layer; wherein at least one of the first selective light modulator layer and the second selective light modulator layer is deposited using a liquid coating process.

The method of claim <NUM>, wherein at least one side of the at least one reflector is free of a selective light modulator layer. The method of claim <NUM>, wherein the at least one reflector is a metallic. The method of claim <NUM>, wherein the liquid coating process comprises adjusting at least one of speed from about <NUM> to about <NUM>/min and a coating gap from about <NUM> to about <NUM> to deposit a wet film from about <NUM> to <NUM> of the selective light modulator layer with a predetermined thickness from about <NUM> to about <NUM>. The method of claim <NUM>, wherein the liquid coating process comprises depositing each of the first and second light modulator layers at a rate of from about <NUM> to about <NUM>/min.

From the foregoing description, those skilled in the art can appreciate that the present teachings can be implemented in a variety of forms. Therefore, while these teachings have been described in connection with particular 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.

Claim 1:
A sheet (<NUM>) comprising:
a reflector (<NUM>) having a first surface, a second surface opposite the first surface, and a third surface;
a first selective light modulator layer (<NUM>) deposited on the first surface of the reflector; and
a second selective light modulator layer (<NUM>') deposited on the second surface of the reflector;
wherein the third surface of the reflector is open; and
wherein at least one of the first selective light modulator layer and the second selective light modulator layer includes a host material and a selective light modulator system including selective light modulator particles including a color shifting particle, a reflective pigment, quantum dots, fluorides, or mixtures thereof, characterized in that
said at least one of the first selective light modulator layer and the second selective light modulator layer further includes a leveling agent.