具体实施方式：
[0005]The figures depict several examples of the present disclosure. However, it should be understood that the present disclosure is not limited to the examples depicted in the figures.
DETAILED DESCRIPTION
[0006]It is to be understood that this disclosure is not limited to the compositions or methods disclosed herein. It is also to be understood that the terminology used in this disclosure is used for describing particular examples. The terms are not intended to be limiting because the scope of the present disclosure is intended to be limited by the appended claims and equivalents thereof.
[0007]It is noted that, as used in this specification and the appended claims, the singular forms “a,”“an,” and “the” include plural referents unless the context clearly dictates otherwise.
[0008]As used in the present disclosure, “liquid vehicle” refers to a liquid in which at least one additive may be dissolved or dispersed to form an inkjet composition. A wide variety of liquid vehicles may be used with the compositions and methods of the present disclosure. A variety of different additives, including, surfactants, solvents, co-solvents, anti-kogation agents, buffers, biocides, sequestering agents, viscosity modifiers, and surface-active agents may be dispersed or dissolved in the liquid vehicle.
[0009]The term “fusing agent” is used herein to describe agents that may be applied to powder bed material, and which may assist in binding or coalescing the powder bed material to form a layer of a 3D part. Heat may be used to fuse the powder bed material, but the fusing agent can also assist in binding powder together, and/or in generating heat from electromagnetic energy (e.g. infrared and near infrared). For example, the fusing agent may become energized or heated when exposed to a frequency or frequencies of electromagnetic radiation. Any additive that assists in binding or fusing particulate powder bed material to form the 3D printed part can be used.
[0010]As used in the present disclosure, “jet,”“jettable,”“jetting,” or the like refers to compositions that are ejected from jetting architecture, such as inkjet architecture. Any suitable inkjet architecture may be used. For example, the inkjet architecture can include thermal or piezo architecture. Additionally, such architecture can be configured to print varying drop sizes, for example, less than about 50 pl, less than about 40 pl, less than about 30 pl, less than about 20 pl, less than about 10 pl. In some examples, the drop size may be about 1 to about 40 pl, for example, about 3 to about 30 pl or about 5 to about 20 picolitres.
[0011]As used in the present disclosure, the term “substantial” or “substantially” when used in reference to a quantity or amount of a material, or a specific characteristic thereof, refers to an amount that is sufficient to provide an effect that the material or characteristic was intended to provide. The exact degree of deviation allowable may in some cases depend on the specific context.
[0012]As used in the present disclosure, the term “build material” may refer to any suitable particulate build material. For example, the build material may comprise polymer, ceramic or metal particles. The build material may also comprise particles of any shape. For example, the particles may be substantially spherical, substantially ovoid, irregularly shaped and/or elongate in shape. In some examples, the particles of build material may be substantially spherical. In some examples, the particles of the build material may take the form of fibers, for instance, cut from longer strands or threads of material.
[0013]As used in the present disclosure, the term “about” is used to provide flexibility to a numerical range endpoint. The degree of flexibility of this term can be dictated by the particular variable and determined based on the associated description herein.
[0014]As used in the present disclosure, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list based on their presentation in a common group without indications to the contrary.
[0015]Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not just the numerical values explicitly recited as the limits of the range, but also to include individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of “about 1 wt % to about 5 wt %” should be interpreted to include not just the explicitly recited values of about 1 wt % to about 5 wt %, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3.5, and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc. This same principle applies to ranges reciting one numerical value. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described.
[0016]The present disclosure relates to a method for three-dimensional printing a light guide plate. The method comprises:[0017]a. forming a plate body by[0018]depositing a layer of transparent build material on a build platform; based on[0019]a 3D object model of the plate body, inkjet printing fusing agent onto at least[0020]a portion of the layer of the transparent build material; and irradiating the fusing agent to heat the transparent build material and at least partially bind the portion of the transparent build material; and[0021]b. forming light scattering features on the plate body by depositing a layer of transparent build material on the plate body; based on a 3D object model of light scattering features, inkjet printing fusing agent and scattering particles onto selected portions of the layer of transparent build material; and irradiating the fusing agent to heat the transparent build material and at least partially bind the portion of the transparent build material.
[0022]The present disclosure also provides a light guide plate obtainable by the method described herein.
[0023]Additionally, the present disclosure provides a light guide plate comprising a plate body having light scattering features, wherein the plate body comprises transparent polymer and plasmonic resonance particles. The plasmonic resonance particles may be dispersed in a matrix of the transparent polymer.
[0024]In some examples, the light scattering layer comprises surface features comprising raised and/or recessed portions and wherein the light scattering layer also comprises scattering particles incorporated therein.
[0025]The present disclosure also provides a display screen, for example, for an electronic device comprising a light guide plate described herein.
[0026]In the present disclosure, a light guide plate body is formed by depositing a layer of transparent build material on a build platform; based on a 3D object model of the plate body, inkjet printing fusing agent onto at least a portion of the layer of the transparent build material; and irradiating the fusing agent to heat the transparent build material and at least partially bind the portion of the transparent build material. For example, because the droplet size and print location of the fusing agent can be digitally controlled, a thin and uniform light guide body may be produced.
[0027]It has also been found that the scattering particles can be introduced at specific locations within the printed part by inkjet printing. For example, because droplet size and print location can be digitally controlled, inkjet compositions containing the scattering particles can be printed in selected amounts at selected locations over the layer of transparent build material. These selected locations may be controlled, such that specific voxels may be selected for printing. When the build material is bound or coalesced following irradiation of the fusing agent, the scattering particles become incorporated into the layer at the selected locations in selected amounts. Furthermore, because fusing agent can also be inkjet printed in selected amounts at selected locations over the layer of transparent build material with a high level of control, surface features can also be introduced as light scattering features with a high degree of accuracy. As a result, intricate light scattering features can be formed on the light guide plate body. These light scattering features can include surface features (e.g. recessed and/or raised portions) as well as scattering particles incorporated at specific locations on the light guide plate. These features can be reproduced with a high degree of accuracy.
[0028]In some examples, the scattering particles may be printed droplet by droplet, wherein each droplet has a volume of less than about 50 pl, for example, less than about 40 pl, less than about 30 pl or less than about 20 pl. In some examples, the scattering particles may be printed at a droplet value of at least about 1 pl, for example, at least about 2 pl or at least about 3 pl. In some examples, the scattering particles may be printed at a droplet volume of about 1 to about 50 pl, for example, about 2 to about 30 pl or about 5 to about 20 pl. This can allow the dopant to be printed, in for example, in patterns (e.g. intricate patterns) throughout the printed part.
[0029]In some examples, the fusing agent is inkjet-printed as a liquid inkjet ink composition comprising the fusing agent using a first print nozzle, and wherein the scattering particles are inkjet printed as a liquid inkjet ink composition comprising the scattering particles using a second print nozzle.
[0030]In some examples, the light scattering features comprise surface features comprising raised and/or recessed features on an outer surface of the light guide plate and scattering particles incorporated in an outer surface of the light guide plate.
[0031]In some examples, the scattering particles are selected from silica, alumina, zirconia, hollow polymer particles and/or titanic.
[0032]In some examples, the light guide plate has a maximum thickness of less than 4 mm.
[0033]In some examples, the fusing agent comprises a plasmonic resonance absorber that absorbs more than about 80% of radiation at wavelengths of about 800 nm to 4000 nm but absorb less than about 20% of radiation having wavelengths of about 400 nm to 780 nm.
[0034]In some examples, the fusing agent comprises plasmonic resonance absorber having the formula (1):
MmM′On (1)
[0035]wherein M is an alkali metal, m is greater than 0 and less than 1, M′ is any metal, and n is greater than 0 and less than or equal to 4.
[0036]M may be lithium (Li), sodium (Na), potassium (K), rubidium (Rb) and/or cesium (Cs).
[0037]In some examples, the fusing agent comprises a plasmonic resonance absorber selected from tungsten bronzes, modified iron phosphates, tetraphenyldiamine-based dyes, metal bis(dithiolene) complexes and modified copper pyrophosphates.
[0038]In some examples, the light guide plate has a refractive index of about 1.49-about 1.60. The light guide plate may have a maximum thickness of less than about 4 mm.
[0039]Build Material
[0040]Any suitable build material may be employed in the present disclosure. The build material may comprise particles or powder.
[0041]In certain examples, the build material particles can have a variety of shapes, such as substantially spherical particles or irregularly-shaped particles. In some examples, the build material particles can be capable of being formed into 3D printed parts with a resolution of about 10 to about 100 μm, for example about 20 to about 80 μm. As used herein, “resolution” refers to the size of the smallest feature that can be formed on a 3D printed part. The build material particles can form layers from about 10 to about 100 μm thick, allowing the fused layers of the printed part (light guide plate) to have roughly the same thickness. This can provide a resolution in the z-axis direction of about 10 to about 100 μm. The build material particles can also have a sufficiently small particle size and sufficiently regular particle shape to provide about 10 to about 100 μm resolution along the x-axis and y-axis.
[0042]In some examples, the particles of the build material can be colorless. For example, the particles of the build material can have a translucent, or transparent appearance. When used, for example, with a colorless fusing composition, such particles can provide a printed part that is substantially transparent.
[0043]In some examples, the build material can be selected from the group consisting of polymeric powder, polymeric-ceramic composite powder, and combinations thereof. Another example of a suitable build material may be glass.
[0044]Suitable build materials include polymer build materials, including, for example, polycarbonate, polyacrylate, cyclo-olefin polymer and polyethylene terephthalate. Examples of suitable polyacrylate include polymethylmethacrylate, PMMA.
[0045]Other examples of polymers suitable for use as the build material particles include polyethylene, polyethylene oxide, polypropylene, polyoxomethylene (i.e., polyacetals), and combinations thereof. Still other examples of suitable build material particles include polystyrene, polyester, polyurethanes, other engineering plastics, and combinations thereof. For example, the build material may be nylon 6 powder, nylon 9 powder, nylon 11 powder, nylon 12 powder, nylon 66 powder, nylon 612 powder, polyethylene powder, thermoplastic polyurethane powder, polypropylene powder, polyester powder, polycarbonate powder, polyether ketone powder, polyacrylate powder, polystyrene powder, or combinations thereof.
[0046]It should be noted that the “combinations” of the polymers described herein can include blends, mixtures, block copolymers, random copolymers, alternating copolymers, periodic polymers, and mixtures thereof.
[0047]In some examples, the build material may be a polymeric-ceramic composite powder. The “polymeric-ceramic composite” powder can include one or more of the polymers described above in combination with one or more ceramic materials in the form of a composite. The polymeric-ceramic composite can include any weight combination of polymeric material and ceramic material. For example, the polymeric material can be present in an amount of up to about 99 wt % with the balance being ceramic material or the ceramic material can be present in an amount of up to about 99 nm with the balance being polymeric material.
[0048]In some examples, the ceramic material can be selected from the group consisting of silica, fused silica, quartz, alumina silicates, magnesia silicates, boriasilicates, and mixtures thereof. Examples of ceramic materials can include metal oxides, inorganic glasses, carbides, nitrides, and borides. Some specific examples can include alumina (Al2O3), Na2O/CaO/SiO2glass (soda-lime glass), silicon nitride (Si3N4), silicon dioxide (SiO2), zirconia (ZrO2), titanium dioxide (TiO2), glass frit materials, or combinations thereof. As an example of one suitable combination, about 30 wt % glass may be mixed with about 70 wt % alumina.
[0049]The build material may be made up of similarly sized particles or differently sized particles. The term “size” or “particle size,” as used herein, refers to the diameter of a substantially spherical particle, or the average diameter of a non-spherical particle (i.e., the average of multiple diameters across the particle), or the effective diameter of a non-spherical particle (i.e., the diameter of a sphere with the same mass and density as the non-spherical particle). A substantially spherical particle (i.e., spherical or near-spherical) has a sphericity of >about 0.84. Thus, any individual particles having a sphericity of <about 0.84 are considered non-spherical (irregularly shaped).
[0050]As used in the present disclosure, “average” with respect to dimensions of particles refers to a volume average unless otherwise specified. Accordingly, “average particle size” refers to a volume average particle size. Additionally, “particle size” refers to the diameter of spherical particles, or to the longest dimension of non-spherical particles. Particle size may be determined by any suitable method, for example, by laser diffraction spectroscopy.
[0051]In some examples, the particle size of the build material particles can be from about 10 μm to about 500 μm, or less than about 450 μm, or less than about 400 μm, or less than about 350 μm, or less than about 300 μm, or less than about 250 μm, or less than about 200 μm, or less than about 150 μm, or less than about 150 μm, or less than about 90 μm, or less than about 80 μm, or at least about 10 μm, or at least about 20 μm, or at least about 30 μm, or at least about 40 μm, or at least about 50 μm, or at least about 60 μm, or at least about 70 μm, or at least about 80 μm, or at least about 90 μm, or at least about 100 μm, or at least about 110 μm, or at least about 120 μm, or at least about 130 μm, or at least about 140 μm, or at least about 150 μm, or at least about 160 μm, or at least about 170 μm, or at least about 180 μm, or at least about 190 μm.
[0052]The build material particles may have a melting point or softening point ranging from about 50° C. to about 400° C. The build material can have a melting or softening point of at least about 60° C., for example, at least about 70° C., at least about 80° C., at least about 90° C., at least about 100° C., at least about 110° C., at least about 120° C., at least about 130° C., at least about 140° C., at least about 150° C. or at least about 160° C. The melting or softening point may be at most about 350° C., for example, at most about 320° C., at most about 300° C., at most about 280° C., at most about 260° C., at most about 240° C. or at most about 220° C.
[0053]In some examples, the melting or softening point may be in the range of about 70° C. to about 350° C. In some examples, the melting or softening point may be in the range of about 80° C. to about 320° C., about 90° C. to about 300° C., about 100° C. to about 280° C., about 110° C. to about 260° C., about 120° C. to about 240° C., about 130° C. to about 220° C., or about 140° C. to about 220° C. In further examples, the polymer can have a melting or softening point from about 150° C. to about 200° C.
[0054]Fusing Agent
[0055]Any suitable fusing agent may be used. In some examples, the fusing agent imparts little or no colour to the finished product.
[0056]The fusing agent can have a temperature boosting capacity. This temperature boosting capacity may be used to increase the temperature of the build material above its melting or softening point. As used herein, “temperature boosting capacity” refers to the ability of a fusing agent to convert infrared (e.g. near-infrared) energy into thermal energy. When fusing agent is applied to the build material (e.g. by inkjet printing), this temperature boosting capacity can be used to increase the temperature of the treated (e.g. printed) portions of the build material over and above the temperature of the untreated (e.g. unprinted) portions of the build material. The particles of the build material can be at least partially bound or coalesced when the temperature increases to or above the melting point of the polymer.
[0057]As used herein, “melting point” refers to the temperature at which a polymer transitions from a crystalline phase to a pliable, amorphous phase. Some materials (e.g. polymers) do not have a single melting point, but rather have a range of temperatures over which the polymers soften. When the fusing agent is selectively applied to at least a portion of the build material layer by inkjet printing, the fusing agent can heat the treated portion to a temperature at or above the melting or softening point, while the untreated portions remain below the melting or softening point. This allows the formation of a solid 3D printed part, while the loose build material can be easily separated from the finished printed part.
[0058]In one example, the fusing agent can have a temperature boosting capacity from about 10° C. to about 70° C., for example, about 15° C. to about 60° C. for a polymer with a melting or softening point of from about 100° C. to about 350° C. If the bed of build material (or powder) is at a temperature within about 10° C. to about 70° C. of the melting or softening point, then such a fusing agent can boost the temperature of the printed powder up to the melting or softening point, while the unprinted build material remains at a lower temperature. In some examples, the build material bed can be preheated to a temperature from about 10° C. to about 70° C. lower than the melting or softening point of the polymer. The fusing agent can then be applied (e.g. printed) onto the build material and the build material bed can be irradiated with a near-infrared light to coalesce the treated (e.g. printed) portion of the build material.
[0059]In some examples, the fusing agent containing a plasmonic resonance absorber e.g. dispersed in an aqueous or non-aqueous vehicle. The plasmonic resonance absorber may absorb at wavelengths ranging from about 800 nm to about 4000 nm and may be transparent at wavelengths ranging from about 400 nm to about 780 nm. As used herein “absorption” means that at least about 80% of radiation having wavelengths ranging from about 800 nm to about 4000 nm is absorbed. As used herein “transparency” means that about 40% or less, for instance, or about 20% or less (e.g. about 15% or less, or about 10% or less) or of radiation having wavelengths ranging from about 400 nm to about 780 nm is absorbed. This absorption and transparency may allow the fusing agent to absorb enough radiation to fuse the build material in contact therewith while causing the 3D part to be substantially uncolored.
[0060]The absorption of the plasmonic resonance absorber may be the result of the plasmonic resonance effects. Electrons associated with the atoms of the plasmonic resonance absorber may be collectively excited by electromagnetic radiation, which may result in collective oscillation of the electrons. The wavelengths required to excite and oscillate these electrons collectively may be dependent on the number of electrons present in the plasmonic resonance absorber particles, which in turn may be dependent on the size of the plasmonic resonance absorber particles. The amount of energy required to collectively oscillate the particle's electrons may be low enough that very small particles (e.g., about 1-100 nm) may absorb electromagnetic radiation with wavelengths several times (e.g., from about 8 to 800 or more times) the size of the particles. The use of these particles allows the fusing agent to be inkjet jettable as well as electromagnetically selective (e.g., having absorption at wavelengths ranging fromabout 800 nm to about 4000 nm and transparency at wavelengths ranging from about 400 nm to about 780 nm).
[0061]In an example, the plasmonic resonance absorber may have an average particle diameter ranging from greater than about 0 nm to less than about 220 nm. In another example the plasmonic resonance absorber has an average particle diameter ranging from greater than about 0 nm to about 120 nm. In a still another example, the plasmonic resonance absorber has an average (e.g. mean) particle diameter ranging from about 10 nm to about 200 nm.
[0062]The amount of the plasmonic resonance absorber that is present in the fusing agent may range from about 0.5 wt % to about 30 wt %, for example, 1 to 20 wt % based on the total wt % of the fusing agent. In some examples, the amount of the plasmonic resonance absorber present in the fusing agent may range from about 1 wt % up to about 15, or, for example, about 3 to about 10 wt % or about 5 to about 8 wt %. In other examples, the amount of the plasmonic resonance absorber may be present in the fusing agent ranges from greater than about 4 wt % up to about 15 wt %. In some examples, these plasmonic resonance absorber loadings may provide a balance between the fusing agent having jetting reliability and electromagnetic radiation absorbance efficiency.
[0063]In an example, the plasmonic resonance absorber may be an inorganic pigment. Suitable plasmonic resonance absorbers are described in WO2017/069778. Examples include lanthanum hexaboride (LaB6), tungsten bronzes (AxWO3), indium tin oxide (In2O3:SnO2, ITO), aluminum zinc oxide (AZO), ruthenium oxide (RuO2), silver (Ag), gold (Au), platinum (Pt), iron pyroxenes (AxFeySi2O6 wherein A is Ca or Mg, x=1.5-1.9, and y=0.1-0.5), modified iron phosphates (AxFeyPO4), and modified copper pyrophosphates (AxCuyP2O7). Tungsten bronzes may be alkali doped tungsten oxides. Examples of suitable alkali dopants (i.e., A in AxWO3) may be cesium, sodium, potassium, or rubidium. In an example, the alkali doped tungsten oxide may be doped in an amount ranging from greater than 0 mol % to about 0.33 mol % based on the total mol % of the alkali doped tungsten oxide. Suitable modified iron phosphates (AxFeyPO4) may include copper iron phosphate (A=Cu, x=0.1-0.5, and y=0.5-0.9), magnesium iron phosphate (A=Mg, x=0.1-0.5, and y=0.5-0.9), and zinc iron phosphate (A=Zn, x=0.1-0.5, and y=0.5-0.9). For the modified iron phosphates, it is to be understood that the number of phosphates may change based on the charge balance with the cations. Suitable modified copper pyrophosphates (AxCuyP2O7) include iron copper pyrophosphate (A=Fe, x=0-2, and y=0-2), magnesium copper pyrophosphate (A=Mg, x=0-2, and y=0-2), and zinc copper pyrophosphate (A=Zn, x=0-2, and y=0-2). Combinations of the inorganic pigments may also be used.
[0064]Other examples of suitable plasmonic resonance absorbers include metal (e.g. nickel) dithiolene complexes. Suitable examples of such plasmonic resonance absorbers are described, for example, in WO 2018/144032, WO 2018/144033 and WO 2018/194542.
[0065]In some examples, the plasmonic resonance absorber may be a metal bis(dithiolene) complex. The metal bis(dithiolene) complex may have the formula:
[0066]wherein:
[0067]M is a metal selected from the group consisting of nickel, zinc, platinum, palladium, and molybdenum; and
[0068]each of W, X, Y, and Z is selected from the group consisting of H, Ph, PhR, and SR, wherein Ph is a phenyl group and R is selected from the group consisting of CnH2n+1, OCnH2+1, and N(CH3)2, wherein 2≤n≤12.
[0069]In some examples, M may be nickel.
[0070]In some examples, the metal bis(thiolene) complex may be dispersed in a polar aprotic solvent. The polar aprotic solvent may be selected from selected from 1-methyl-2-pyrrolidone, 2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and a combination thereof.
[0071]The polar aprotic solvent may be included to at least partially dissolve and reduce the metal bis(dithiolene) complex and to help to shift the absorption of the metal bis(dithiolene) complex.
[0072]In some instances, the shift can be further into the near-infrared (NIR) region (e.g., shifting from an absorption maximum of about 850 nm when the metal bis(dithiolene) complex is not reduced to an absorption maximum of about 940 nm when metal bis(dithiolene) complex is reduced (e.g., to its monoanionic form or to its dianionic form). The electron donor compound can shift the absorption maximum of the metal bis(dithiolene) complex by reducing the metal bis(dithiolene) complex to its monoanionic form or to its dianionic form. When the metal bis(dithiolene) complex is reduced to its monoanionic form or to its dianionic form, the color of the metal bis(dithiolene) complex can change. For example, the initial reduction of a nickel bis(dithiolene) complex to its monoanionic form may result in the color changing from green to reddish brown. For example, the further reduction of a nickel bis(dithiolene) complex to its dianionic form may result in the color changing to become substantially colorless. The substantially colorless complex can still absorb infrared radiation.
[0073]In some examples, the metal bis(thiolene) complex may be used used in combination with an electron donor compound. The electron donor compound may be the electron donor compound can comprise at least one hindered amine light stabilizer (HALS) compound.
[0074]The HALS term is a general term for compounds that can have a 2,2,6,6-tetramethylpiperidine skeleton and are broadly categorized according to molecular weight. An example may be bis(2,2,6,6,-tetramethyl-4-piperidyl)sebacate.
[0075]The electron donor compound can facilitate the reduction of the metal bis(dithiolene) complex in combination with a polar aprotic solvent described herein. Without wishing to be bound by theory, the electron donor compound can render the metal bis(dithiolene) complex readily reducible and thus more soluble in the polar aprotic solvent. The reduction of the metal bis(dithiolene) complex to its monoanionic form or to its dianionic form can take place in the absence of the electron donor compound. However, this may require exposure to e.g. elevated temperatures.
[0076]In other examples, the plasmonic resonance absorber may be a tetraphenyldiamine-based dye. Such dyes are described in WO 2018/144031. Such dyes may be used in combination with alkyldiphenyloxide disulfonate and 1-methyl-2-pyrrolidone.
[0077]In some examples, the plasmonic resonance absorber may comprise at least one nanoparticle comprising: at least one metal oxide. The metal oxide may absorb infrared light in a range of from about 780 nm to about 2300 nm. The metal oxide may have the formula shown in formula (1):
MmM′On (1)
[0078]wherein M is an alkali metal, m is greater than 0 and less than 1, M′ is any metal, and n is greater than 0 and less than or equal to 4. The nanoparticle may have a diameter of from about 0.1 nm to about 500 nm.
[0079]In some examples, the metal oxide can be defined as shown in formula (1) below:
MmM′On (1).
[0080]M in formula (1) above can be an alkali metal. In some examples, M can be lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), or mixtures thereof. In some examples, M can be cesium (Cs).
[0081]m in formula (1) above can be greater than 0 and less than 1. In some examples, m can be 0.33.
[0082]M′ in formula (1) above can be any metal. In some examples, M′ can be tungsten (W), molybdenum (Mb), tantalum (Ta), hafnium (Hf), cerium (Ce), lanthanum (La), or mixtures thereof. In some examples, M′ can be tungsten (W).
[0083]n in formula (1) above can be greater than 0 and less than or equal to 4. In some examples, n in formula (1) above can be greater than 0 and less than or equal to 3. The metal oxide can be an IR absorbing inorganic nanoparticle. In some examples, the metal oxide can absorb infrared light in a range of from about 780 nm to about 2300 nm, or from about 790 nm to about 1800 nm, or from about 800 nm to about 1500 nm, or from about 810 nm to about 1200 nm, or from about 820 nm to about 1100 nm, or from about 830 nm to about 1000 nm.
[0084]In some examples, the metal oxide nanoparticles can have a diameter of from about 0.01 nm to about 400 nm, or from about 0.1 nm to about 350 nm, or from about 0.5 nm to about 300 nm, or from about 0.7 nm to about 250 nm, or from about 0.8 nm to about 200 nm, or from about 0.9 nm to about 150 nm, or from about 1 nm to about 100 nm, or from about 1 nm to about 90 nm, or from about 1 nm to about 80 nm, or from about 1 nm to about 70 nm, or from about 1 nm to about 60 nm, or from about 2 nm to about 50 nm, or from about 3 nm to about 40 nm, or from about 3 nm to about 30 nm, or from about 3 to about 20 nm, or from about 3 to about 10 nm.
[0085]Unless otherwise indicated, by diameter, it is meant mean particle diameter, for example, mean particle diameter by volume or weight (e.g. by volume). The diameter may be determined by any suitable measuring method. Example