Method of three-dimensional printing, jettable antioxidant formulation, multi-fluid kit

Abstract

One example of a jettable antioxidant formulation is used for three-dimensional (3D) printing. The jettable antioxidant formulation includes an antioxidant blend; a surfactant, a dispersant, or a combination thereof; a water-soluble or water-miscible organic co-solvent; and water. The antioxidant blend consists of a primary antioxidant and a secondary antioxidant.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to methods of three-dimensional printing, jettable antioxidant formulations, multi-fluid kits. BACKGROUND

[0002] Three-dimensional (3D) printing can be an additive printing method for making three-dimensional solid parts from a digital model. 3D printing is often used for rapid product prototyping, mold generation, mold master generation, and small batch manufacturing. Some 3D printing techniques are considered additive processes because they involve the application of successive layers of material, which in some instances can include a build material, a binding agent, and / or one or more other printing liquids or combinations thereof. This is in contrast to traditional machining processes, which generally rely on the removal of material to create the final part. Some 3D printing methods use a chemical binding agent or glue to bind the build material together. Other 3D printing methods involve at least partial solidification, thermal fusing / merging, melting, sintering, etc. of the build material, and the material coalescence mechanism can depend on the type of build material used. For some materials, at least partial melting can be achieved using heat-assisted extrusion, and for other materials, such as polymerizable materials, solidification or fusing can be achieved using, for example, ultraviolet or infrared light. SUMMARY

[0003] A method of three-dimensional (3D) printing, comprising: applying a polymeric build material composition to form a build material layer; selectively applying a fusing agent on at least a portion of the build material layer based on a 3D object model; selectively applying an antioxidant formulation on at least the portion of the build material layer based on the 3D object model, wherein the antioxidant formulation comprises: water; a water-soluble or water-miscible organic co-solvent; a surfactant, a dispersant, or a combination thereof; and an antioxidant blend consisting of a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant is a hydrogen atom or an electron donor and the secondary antioxidant is a peroxide scavenger; and exposing the build material layer to electromagnetic radiation to coalesce at least the portion to form a layer of a 3D object.

[0004] SUMMARY

[0005] The features of the examples of the present disclosure will be apparent to those skilled in the art, from the following detailed description and drawings, wherein like reference numerals refer to like but possibly not identical components. For the sake of brevity, the description of a feature or component of a drawing can not be repeated at every occurrence of such feature or component.

[0006] Figure 1 is a flowchart depicting one example of a 3D printing method;

[0007] Figure 2 is a schematic diagram of one example of a 3D printing method of Figure 1 ;

[0008] Figure 3 is a flow chart depicting another example of a 3D printing method;

[0009] Figure 4 is a schematic diagram of one example of a 3D printing method; Figure 3

[0010] Figure 5 is a cross-sectional view of an example 3D object;

[0011] Figure 6 is a flow chart depicting another example of a 3D printing method;

[0012] Figure 7 is a cross-sectional view of another example 3D object;

[0013] Figure 8 is a graph depicting b* of a fresh (unaged) build material, and one example build material and two comparative build materials after exposure to an oven aging test; and

[0014] Figures 9A to 9D is a black and white reproduction of a color photograph depicting a fresh (unaged) build material, and one example build material and two comparative build materials after exposure to an oven aging test. DETAILED DESCRIPTION

[0015] Some examples of three-dimensional (3D) printing can utilize a fusing agent (comprising an electromagnetic radiation absorber) to pattern a polymeric build material. In these examples, an entire layer of polymeric build material is exposed to electromagnetic radiation, but a patterned area of the polymeric build material (which in some cases is less than the entire layer) fuses / coalesces and hardens to become a layer of a 3D part. In the patterned area, the fusing agent can at least partially infiltrate the voids between the polymeric build material particles, and can also spread onto the outer surfaces of the polymeric build material particles. This fusing agent can absorb radiation and convert the absorbed radiation into thermal energy, which in turn fuses / coalesces the polymeric build material in contact with the fusing agent. The fusing / coalescing causes the polymeric build material to connect or blend to form a single entity (i.e., a layer of a 3D part). The fusing / coalescing can involve at least partial thermal bonding, melting, adhesion, and / or some other mechanism of coalescing the polymeric build material to form a layer of a 3D part.

[0016] ​These examples of three-dimensional (3D) printing can also include a pre-heat process, in which an entire layer of the polymeric build material is heated (e.g., to a temperature that is about 5 °C to about 50 °C below the melting point or melting range of the polymeric build material) prior to electromagnetic radiation exposure. Pre-heating increases the build material temperature, thereby reducing the amount of thermal energy expended in subsequent processing to raise the polymeric build material above its melting point.

[0017] Throughout the printing cycle (i.e., patterning and fusing), the polymeric build material can be exposed to high temperatures for long periods of time. Moreover, the high temperature exposure can occur in an air environment (i.e., an environment containing 20% or more oxygen by volume) or another oxygen-containing environment. Long-term exposure to high temperatures in an oxygen-containing environment can cause thermal degradation of the polymeric build material. For example, exposure to high temperatures in an oxygen-containing environment can cause chain scission to occur at the amide functionality of a polyamide build material. Thermal degradation can cause discoloration (e.g., yellowing or browning) of the 3D object and / or can reduce the quality of the 3D object. Thermal degradation can also cause discoloration of the non-patterned polymeric build material and thereby can reduce the reusability / recyclability of the non-patterned polymeric build material.

[0018] Disclosed herein are antioxidant formulations that can be used throughout a 3D printing process. The antioxidant formulations are jettable, such that the formulations can be applied at a voxel level in a controlled (and possibly varying) manner. The ability to jet the antioxidant formulations during a 3D printing process can help to stabilize the polymeric build material as printing is being performed, and thereby can reduce discoloration of the 3D printed object and improve the quality of the 3D printed object, and / or can reduce discoloration of the non-patterned polymeric build material and improve the reusability / recyclability of the non-patterned polymeric build material.

[0019] Throughout the present disclosure, weight percent as "wt. % active" refers to the loading of the active component of a dispersion or other formulation, e.g., antioxidant formulation, fusing agent, detailing agent, etc. For example, an energy absorber, such as carbon black, can be present in a water-based formulation (e.g., stock solution or dispersion) prior to incorporation into a fusing agent vehicle. In this example, the wt. % active of the carbon black accounts for the loading (as wt. %) of the carbon black solids present in the fusing agent, and does not account for the weight of other components (e.g., water, etc.) present in the stock solution or dispersion with the carbon black. The term "wt. %" without the term "active" refers to i) the loading of 100% active component (in the antioxidant formulation, fusing agent, etc.) exclusive of other non-active components therein, or ii) the loading of a material or component (in the antioxidant formulation, fusing agent, etc.) used "as is," such that the wt. % accounts for active and non-active components.

[0020] 3D printing multi-fluid kits and 3D printing kits

[0021] Examples disclosed herein include multi-fluid kits and 3D printing kits for 3D printing.

[0022] One example of a multi-fluid kit for 3D printing includes a fusing agent comprising water and an electromagnetic radiation absorber; and an antioxidant formulation comprising water and an antioxidant blend consisting of a primary antioxidant and a secondary antioxidant. Some examples of the multi-fluid kit further include a colorant selected from a black ink, a cyan ink, a magenta ink, or a yellow ink; or a detailing agent comprising a surfactant, a co-solvent, and water; or both a colorant and a detailing agent.

[0023] Any example of a multi-fluid kit can also be part of a 3D printing kit. In addition to the fluids of the multi-fluid kit, the 3D printing kit includes a polymeric build material composition.

[0024] It is understood that the fluids of the multi-fluid kit or the fluids and composition of the 3D printing kit can be stored separately until used together in an example of a 3D printing method disclosed herein. The fluids and / or composition can each be contained in one or more containers prior to and during printing, but can be combined together during the printing process. The containers can be any type of vessel (e.g., reservoir), box, or receptacle made of any material.

[0025] As used herein, it is understood that the term "material set" or "kit" is synonymous with "composition" in some instances.

[0026] As mentioned, various fluids and / or one or more compositions can be included in the fluid kits and / or 3D printing kits disclosed herein. Exemplary compositions of antioxidant formulations, fusing agents, detailing agents, colorants, and build material compositions will now be described.

[0027] Antioxidant Formulation

[0028] The antioxidant formulation includes an antioxidant blend consisting of a primary antioxidant and a secondary antioxidant; a surfactant, a dispersant, or a combination thereof; a water-soluble or water-miscible organic co-solvent; and water. In some examples, the antioxidant formulation consists of these components. In other examples, the antioxidant formulation can include other additives, such as a buffer.

[0029] The antioxidant formulation can be prepared by first preparing a dispersion of the primary antioxidant and the secondary antioxidant and then combining the dispersion with other liquid components, such as the co-solvent, water, etc.

[0030] The antioxidant dispersion includes a primary antioxidant; a secondary antioxidant; a surfactant, dispersant, or combination thereof; and water.

[0031] The primary antioxidant is a free radical scavenger that acts as a hydrogen atom or electron donor to quench polymer free radicals (reactive radicals such as carbon-centered radicals and peroxy radicals). Quenching the free radicals of the polymer build material destroys their ability to continue the free radical chain growth process and thereby stabilizes the polymer build material.

[0032] In one example, the primary antioxidant can be a hindered phenol, such as a bis-hindered phenol. Examples of suitable bis-hindered phenols include 245 (ethylene bis (oxyethylene) bis- (3- (5-tert-butyl-4-hydroxy-m-tolyl) -propionic acid), having the following structure:

[0033]

[0034] 1098 (benzenepropanamide, N,N'-1,6-hexanediylbis(3,5-bis(1,1-dimethylethyl)-4- hydroxy)); 254 (a mixture of 40% triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl), polyvinyl alcohol, and deionized water); and 2,2'-methylenebis(6-tert-butyl-4-methylphenol).

[0035] The secondary antioxidant reacts with intermediate degradation products of polymer free radicals and molecular oxygen (e.g., hydroperoxides) to stabilize the polymer build material. For example, the secondary antioxidant is a peroxide scavenger. Peroxides are prone to decompose into free radicals that can further oxidize the polymer build material. The secondary antioxidant can prevent this degradation pathway by reacting with the peroxide and decomposing it into non-reactive products before the peroxide decomposes into alkoxy and hydroxyl radicals.

[0036] Various examples of secondary antioxidants can include thioethers, thioesters, and phosphites.

[0037] In one example, the thioether can be dilauryl thiodipropionate, which is also known as dilaurylthiodipropionate (DLTDP). DLTDP is sometimes also described as a thioester. Dilauryl thiodipropionate has the following chemical formula:

[0038]

[0039] and under the trade name DLTDP is available from Struktol Company of America. In another example, the thioether can be 3,3'-thiodipropionic acid di-octadecyl ester (DSTDP). 3,3'-thiodipropionic acid di-octadecyl ester has the following chemical formula:

[0040]

[0041] and under the trade name DSTDP is available from Struktol Company of America. Still other examples of thioethers include pentaerythritol tetrakis(β-laurylthiopropionate) and thio-bis[2-(l,l-dimethylethyl)-5-methyl-4,l-phenylene] bis[3-(dodecylthio)propionate]. Although some examples of thioethers have been provided, it is believed that other thioesters or thioethers can be used.

[0042] Examples of suitable inorganic phosphites include tris(2,4-di-tert- butylphenyl) phosphite, 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphospha- spiro[5.5]undecane, or combinations thereof. One commercially available example includes H10 (an inorganic phosphite available from Bruggemann Chemical).

[0043] The primary antioxidant and the secondary antioxidant together comprise an antioxidant blend. In one example of the antioxidant blend, the primary antioxidant is a hindered phenol; and the secondary antioxidant is selected from the group consisting of a thioether, a thioester, a phosphite, and combinations thereof.

[0044] Without being bound by any theory, it is believed that the antioxidant blend exhibits a synergistic effect that helps to reduce degradation of the polymeric build material. In particular, hydrogen bonding between the hydroxyl groups of the primary antioxidant and the oxygen of the secondary antioxidant can contribute to the synergistic effect of the antioxidant blend. The hydrogen bonding can ensure that the functional group(s) of the secondary antioxidant are in the vicinity when the functional group(s) of the primary antioxidant fulfill their function.

[0045] In the antioxidant formulation, it is desirable for the antioxidant blend (i.e., the primary antioxidant and the secondary antioxidant) to be present in an amount of about 1 wt.% active to about 15 wt.% active of the total weight of the antioxidant formulation. In some examples, the antioxidant blend is present in the antioxidant formulation in an amount of about 2 wt.% active to about 10 wt.% active of the total weight of the antioxidant formulation. In still other examples, the antioxidant blend is present in the antioxidant formulation in an amount of about 2 wt.% active to about 5 wt.% active, or about 3 wt.% active to about 4 wt.% active of the total weight of the antioxidant formulation.

[0046] The desired amount of antioxidant blend in the final antioxidant formulation will be determined in part by the amount of each of the primary antioxidant and the secondary antioxidant used in the dispersion. When preparing a dispersion of a primary antioxidant and a secondary antioxidant, the respective amounts of the primary antioxidant and the secondary antioxidant used will depend at least in part on how much of the dispersion is included in the antioxidant formulation and the percent of active of the antioxidant raw material. In the dispersion, the antioxidant blend (i.e., both the primary antioxidant and the secondary antioxidant) can be present in an amount of about 5 wt. % active to about 30 wt. % active of the total weight of the dispersion.

[0047] In the dispersion and in the final antioxidant formulation, it can be desirable for the primary antioxidant and the secondary antioxidant to be present in a weight ratio of about 1 : 1 to about 1 :5. In some examples, it can be desirable to use the secondary antioxidant in an amount that exceeds the primary antioxidant, such that the weight ratio of the primary antioxidant to the secondary antioxidant is about 1 :2 to about 1 :5, or about 1 : 1.5 to about 1 :4, or about 1 :2 to about 1 :3, and the like.

[0048] The dispersion includes the primary antioxidant and the secondary antioxidant in water. Many secondary antioxidants can not be miscible with water. Accordingly, a surfactant, a dispersant, or a combination thereof can be included in the dispersion to aid in dispersing the secondary antioxidant.

[0049] The surfactant can be any anionic, cationic, or non-ionic surfactant that can sufficiently disperse the antioxidant in water. In one example, the surfactant included in the dispersion is sodium stearate, stearyl alcohol, or a combination thereof. These surfactants can also aid in the dispersibility.

[0050] The dispersant can be selected from styrene acrylic copolymers, poly(vinyl alcohol), vinyl alcohol copolymers, and combinations thereof. Some specific examples of suitable dispersants include water-soluble styrene-acrylic copolymers / resins, such as 296、 671、 678、 680、 683、 690 and the like, and poly(vinyl alcohol), such as those in the series available from Kuraray Europe GmbH. Examples of suitable vinyl alcohol copolymers include poly(vinyl alcohol-co-ethylene) (e.g., 27 mol% or 32 mol% ethylene).

[0051] In one example, the dispersion (and thus the final formulation) includes a surfactant and a dispersant; the surfactant is a mixture of stearyl alcohol and sodium stearate; and the dispersant is selected from the group consisting of styrene acrylic, poly(vinyl alcohol), ethylene vinyl alcohol copolymer, and combinations thereof.

[0052] Regardless of whether the surfactant or dispersant is used alone or in combination, the total amount of surfactant(s) and / or dispersant(s) can be from about 0.01 wt% to about 10 wt% based on the total weight of the dispersion. In some specific examples, the surfactant(s) and / or dispersant(s) can be from about 0.5 wt% to about 5 wt%, or from about 0.1 wt% to about 2 wt% based on the total weight of the dispersion.

[0053] In one example of a method of making the dispersion, the primary antioxidant and the secondary antioxidant are combined and melted with the surfactant and / or dispersant. The primary antioxidant and the secondary antioxidant can have a relatively low melting point such that the antioxidants can be melted. The melted antioxidants can then be emulsified in water. In certain examples, each antioxidant has a melting point of from about 30 °C to about 150 °C. In other examples, each antioxidant has a melting point of from about 40 °C to about 120 °C, or from about 50 °C to about 100 °C. The melting temperature will depend on the antioxidants used, but in one example is from about 100 °C to about 150 °C.

[0054] The melted mixture can then be cooled to a temperature of, for example, from about 60 °C to about 80 °C.

[0055] The mixture can also be stirred throughout the melting and cooling processes.

[0056] Water and a basic aqueous solution can then be added to the cooled mixture to form a relatively viscous, but still stirrable, paste. Any basic aqueous solution can be used, including potassium hydroxide (KOH) solution, sodium hydroxide (NaOH) solution, and the like. The concentration of the basic aqueous solution can be from about 10% to about 60%. In some examples, the concentration of the basic aqueous solution can be from about 20% to about 50%, or from about 40% to about 60%. In one example, the basic aqueous solution is a 50% KOH solution. The basic aqueous solution can be added in an amount of from about 0.01 wt% active to about 0.5 wt% active based on the total weight of the dispersion.

[0057] Additional water can then be added to form an emulsion of the melted antioxidants. The emulsion can then be cooled to form a dispersion of solid antioxidant blend particles.

[0058] While exemplary emulsification conditions have been described, it is to be understood that the conditions can vary depending on the primary antioxidant and secondary antioxidant used.

[0059] The particle size of the antioxidant blend particles in the dispersion can be reduced by milling. It can be desirable to reduce the particle size of the antioxidant blend particles so that they are small enough to be easily jettable (e.g., using a thermal inkjet print head or a piezoelectric inkjet print head). As one example, the particles can have an average particle size of about 10 nm to about 800 nm. In other examples, the antioxidant blend particles can have an average particle size of about 10 nm to about 500 nm, or about 20 nm to about 100 nm. The particle size of the antioxidant blend particles can be reduced, for example, by grinding or milling. As used herein, the term "average particle size" refers to the number- or volume-weighted average diameter of the particle distribution.

[0060] The dispersion is then combined with other liquid components to form an antioxidant formulation. These other liquid components can include additional water, a water-soluble or water-miscible organic co-solvent (e.g., selected to aid in jetability), and in some examples, a surfactant and / or a buffer.

[0061] Classes of water-soluble or water-miscible organic co-solvents that can be used include aliphatic alcohols, aromatic alcohols, glycols, glycol ethers, polyglycol ethers, lactams, formamides (substituted and unsubstituted), acetamides (substituted and unsubstituted), glycols, and long chain alcohols. Examples of these co-solvents include aliphatic primary alcohols, aliphatic secondary alcohols, 1,2-alcohols, 1,3-alcohols, 1,5-alcohols, 1,6-hexanediol or other glycols (e.g., 1,2-propanediol, 1,5-pentanediol, 2-methyl-1,3-propanediol, etc.), higher homologs of ethylene glycol alkyl ethers (C6-C 12 ), triethylene glycol, tetraethylene glycol, tripropylene glycol methyl ether, N-alkyl caprolactam, unsubstituted caprolactam, 2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, and the like. Other examples of organic co-solvents include dimethyl sulfoxide (DMSO), isopropyl alcohol, ethanol, amyl alcohol, acetone, and the like.

[0062] The one or more co-solvents can be present in the antioxidant formulation in a total amount of about 1 wt% to about 20 wt%, based on the total weight of the antioxidant formulation. In one example, the antioxidant formulation comprises about 2 wt% to about 15 wt%, or about 5 wt% to about 10 wt%, of one or more co-solvents.

[0063] One or more surfactants suitable for the antioxidant formulation include nonionic, anionic, or cationic surfactants. Some exemplary surfactants include alkyl polyethylene oxide, alkyl phenyl polyethylene oxide, polyethylene oxide block copolymer, acetylenic polyethylene oxide, polyethylene oxide (di)esters, polyethylene oxide amine, protonated polyethylene oxide amine, protonated polyethylene oxide amide, dimethicone copolyol, substituted amine oxide, fluorosurfactant, and the like. Some specific examples include self-emulsifiable nonionic wetting agents based on acetylenic diol chemistry (e.g., DYNOL® SEF from Evonik Degussa), nonionic fluorosurfactants (e.g., ZONYL® FS- 10 from DuPont), fluorosurfactants (e.g., FLUORAD® FS-35 from Chemours), ethoxylated low foam wetting agents (e.g., DYNOL® 440 or DYNOL® 460 from Evonik Degussa), ethoxylated wetting agents and molecular defoamers (e.g., DYNOL® 420 from Evonik Degussa), nonionic wetting agents and molecular defoamers (e.g., DYNOL® 104E from Evonik Degussa), and / or water soluble nonionic surfactants (e.g., TERGITOL™N-6, TERGITOL™ 15-S-7, or TERGITOL™ 15-S-9 (secondary alcohol ethoxylate) from The Dow Chemical Company, or DOWFAX® Wet 510 (organic surfactant) available from Evonik Degussa). Yet another suitable (anionic) surfactant includes alkyl diphenyloxide disulfonate (e.g., DOWFAX® series, such as 2A1, 3B2, 8390, C6L, C10L, and 30599 from The Dow Chemical Company). TM TM TM TM

[0064] Regardless of whether a single surfactant or a combination of surfactants is used, the total amount of the one or more surfactants in the antioxidant formulation can be from about 0.01 wt. % active to about 3 wt. % active, based on the total weight of the antioxidant formulation. In one example, the total amount of the one or more surfactants in the antioxidant formulation can be about 0.07 wt. % active, based on the total weight of the antioxidant formulation.

[0065] ​​​​​​​​​​​​The antioxidant formulation can also include a buffer to prevent undesirable changes in pH. In one example, the antioxidant formulation can have a pH of about 6 to about 10. In another example, the antioxidant formulation can have a pH of about 6.5 to about 9.5. Examples of buffers include TRIS (tris(hydroxymethyl)aminomethane or ), TRIS or hydrochloride, bis-tris propane, TES (2-[(2-hydroxy-1,1 -bis(hydroxymethyl)ethyl)amino]ethanesulfonic acid), MES (2-mesethanesulfonic acid), MOPS (3-(N-morpholino)propanesulfonic acid), HEPES (4-(2-hydroxyethyl)-1 -piperazineethanesulfonic acid), DIPSO (3-(N,N-bis[2-hydroxyethyl]amino)-2-hydroxypropanesulfonic acid), Tricine (N-[tris(hydroxymethyl)methyl]glycine), HEPPSO (beta-hydroxy-4-(2-hydroxyethyl)-1 -piperazinepropanesulfonic acid monohydrate), POPSO (piperazine-1,4-bis(2-hydroxypropanesulfonic acid) dihydrate), EPPS (4-(2-hydroxyethyl)-1 -piperazinepropanesulfonic acid, 4-(2-hydroxyethyl)piperazine-1 -propanesulfonic acid), TEA (triethanolamine buffer solution), Gly-Gly (diglycine), bicine (N,N-bis(2-hydroxyethyl)glycine), HEPBS (N-(2-hydroxyethyl)piperazine-N'-(4-butanesulfonic acid)), TAPS ([tris(hydroxymethyl)methylamino]propanesulfonic acid), AMPD (2-amino-2-methyl-1,3-propanediol), TABS (N-tris(hydroxymethyl)methyl-4-aminobutanesulfonic acid), and the like.

[0066] Regardless of whether one buffer or a combination of buffers is used, the total amount of the one or more buffers in the antioxidant formulation can be greater than 0 wt. % active to about 1 wt. % active, based on the total weight of the antioxidant formulation. In another example, the buffer is present in other amounts, such as about 0.25 wt. % active to about 0.75 wt. %, based on the total weight of the antioxidant formulation. In one example, the one or more buffers are present in the antioxidant formulation in an amount of about 0.5 wt. % active, based on the total weight of the antioxidant formulation.

[0067] The antioxidant formulation can also include ingredients that improve jetting through an applicator, such as an inkjet printhead. In some examples, the antioxidant formulation can include jetting-imparting ingredients, such as those described above in the fusing agents. These ingredients can include one or more antimicrobial agents, one or more viscosity modifiers, one or more sequestering or chelating agents, and the like. These ingredients can be included in any amounts described above in the fusing agents.

[0068] Fusing agent

[0069] One or more fluid sets and / or one or more 3D printing sets disclosed herein include one or more fusing agents.

[0070] Some examples of fusing agents have significant absorption (e.g., 80%) at least in the visible region (400 nm - 780 nm). These examples of fusing agents are referred to as core fusing agents, or in some cases, black fusing agents. As described herein, the energy absorbers (or active materials) in core fusing agents can also absorb energy in the infrared region (e.g., 800 nm to 4000 nm). This absorption generates heat suitable for coalescing / fusing the build material composition in contact therewith during a 3D printing process, which results in 3D objects (or regions of 3D objects) having mechanical integrity and relatively uniform mechanical properties (e.g., strength, elongation at break, etc.). However, this absorption also results in strongly colored, e.g., black, 3D objects (or regions of 3D objects).

[0071] Other examples of fusing agents include energy absorbers that have absorption at wavelengths from 800 nm to 4000 nm and transparency at wavelengths from 400 nm to 780 nm. These examples of fusing agents are referred to as primer fusing agents, or in some cases, low-color fusing agents. This absorption and transparency enable primer fusing agents to absorb sufficient radiation to coalesce / fuse the build material composition in contact therewith while resulting in 3D objects (or regions of 3D objects) that are white or light-colored.

[0072] Still other examples of energy absorbers absorb at least some wavelengths in the range from 400 nm to 4000 nm. Examples include glass fibers, titanium dioxide, clays, mica, talc, barium sulfate, calcium carbonate, phosphate pigments, silicate pigments, and / or natural filler materials such as nanocellulose. These energy absorbers are typically white or light-colored and can be used in core fusing agents or primer fusing agents.

[0073] Phosphates can have a variety of counterions such as copper, zinc, iron, magnesium, calcium, strontium, and the like, and combinations thereof. Examples of phosphates can include M2P2O7, M4P2O9, M5P2O 10 , M3(PO4)2, M(PO3)2, M2P4O 12and combinations thereof, where M represents a counterion having an oxidation state of +2, such as those listed above or combinations thereof. For example, M2P2O7 can include compounds such as Cu2P2O7, Cu / MgP2O7, Cu / ZnP2O7, or any other suitable combination of counterions. Silicates can have the same or similar counterions as the phosphates. Exemplary silicates can include M2SiO4, M2Si2O6, and other silicates where M is a counterion having an oxidation state of +2. For example, the silicate M2Si2O6 can include Mg2Si2O6, Mg / CaSi2O6, MgCuSi2O6, Cu2Si2O6, Cu / ZnSi2O6, or other suitable combinations of counterions. It is noted that the phosphates and silicates described herein are not limited to counterions having an oxidation state of +2, other counterions can also be used to make other suitable near-infrared pigments.

[0074] As used herein, “absorbs” means absorbing at least 80% of radiation having a wavelength within a specified range. As used herein, “transparent” means absorbing 25% or less of radiation having a wavelength within a specified range.

[0075] Core fusing agent

[0076] In some examples, the fusing agent is a core fusing agent and the electromagnetic radiation absorber has an absorption at least at wavelengths from 400 nm to 780 nm. Some examples of core fusing agents are dispersions containing an electromagnetic radiation absorber (i.e., an active material). In some examples, the active material can be an infrared absorbing colorant. In one example, the active material is a near-infrared absorbing colorant. Any near-infrared colorant can be used in a core fusing agent, such as those produced by Fabricolor, Eastman Kodak, BASF, or Yamamoto. As one example, the core fusing agent can be a print liquid formulation containing carbon black as the active material. Examples of such print liquid formulations are commercially known as CM997A, 516458, C18928, C93848, C93808, and the like, all available from HP Inc.

[0077] As another example, the core fusing agent can be a print liquid formulation containing a near-infrared absorbing dye as the active material. Examples of such print liquid formulations are described in U.S. Patent 9,133,344, which is incorporated herein by reference in its entirety. Some examples of near-infrared absorbing dyes are water-soluble near-infrared absorbing dyes selected from the group consisting of:

[0078]

[0079]

[0080]

[0081]

[0082] and mixtures thereof. In the above formulations, M can be a divalent metal atom (e.g., copper, etc.), or if the metal is more than divalent (e.g., indium, etc.), can have OSO3Na axial groups filling any unfilled valence state, R can be hydrogen or any Ci-C8alkyl group (including substituted and unsubstituted alkyl groups), and Z can be a counterion such that the overall charge of the near infrared absorbing dye is neutral. For example, the counterion can be sodium, lithium, potassium, NH4 + and the like.

[0083] Other examples of near infrared absorbing dyes are hydrophobic near infrared absorbing dyes selected from the group consisting of:

[0084]

[0085]

[0086]

[0087] and mixtures thereof. For the hydrophobic near infrared absorbing dyes, M can be a divalent metal atom (e.g., copper, etc.), or if the metal is more than divalent, can include metals having Cl, Br, or OR' (R' = H, CH3, COCH3, COCH2COOCH3, COCH2COCH3) axial groups filling any unfilled valence state, and R can be hydrogen or any Ci-C8alkyl group (including substituted and unsubstituted alkyl groups).

[0088] Other near infrared absorbing dyes or pigments can be used in the core fusing agent. Some examples include anthraquinone dyes or pigments, metal dithiolene dyes or pigments, cyanine dyes or pigments, perylene diimine dyes or pigments, croconium dyes or pigments, pyrilium or thiopyrilium dyes or pigments, boron-dipyrromethene dyes or pigments, or azaboron-dipyrromethene dyes or pigments.

[0089] Anthraquinone dyes or pigments and metal (e.g., nickel) dithiolene dyes or pigments can have the following structures, respectively:

[0090]

[0091] wherein R in the anthraquinone dye or pigment can be hydrogen or any Ci-C8alkyl group (including substituted and unsubstituted alkyl groups), and R in the dithiafulvene can be hydrogen, COOH, SO3, NH2, any Ci-C8alkyl group (including substituted and unsubstituted alkyl groups), and the like.

[0092] The cyanine dye or pigment and the perylene diimide dye or pigment can have the following structures, respectively:

[0093]

[0094] wherein R in the perylene diimide dye or pigment can be hydrogen or any Ci-C8alkyl group (including substituted and unsubstituted alkyl groups).

[0095] The croconium dye or pigment and the pyrylium or thiapyrylium dye or pigment can have the following structures, respectively:

[0096]

[0097] The boron-dipyrromethene dye or pigment and the aza-boron-dipyrromethene dye or pigment can have the following structures, respectively:

[0098]

[0099] Other suitable near-infrared absorbing dyes can include aminium dyes, tetraaryl diamine dyes, phthalocyanine dyes, and the like.

[0100] Other near-infrared absorbing materials include conjugated polymers (i.e., polymers having a backbone with alternating double and single bonds), such as poly(3,4- ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), polythiophene, poly(p- phenylene sulfide), polyaniline, poly(pyrole), poly(ethyne), poly(p-phenylene vinylene), polyparaphenylene, or combinations thereof.

[0101] The amount of energy absorbing / active material present in the core fusing agent is greater than 0 wt% active to about 40 wt% active, based on the total weight of the core fusing agent. In other examples, the amount of active material in the core fusing agent is about 0.3 wt% active to 30 wt% active, about 1 wt% active to about 20 wt% active, about 1.0 wt% active to about 10.0 wt% active, or greater than 4.0 wt% active to about 15.0 wt% active. It is believed that these active material loadings provide a balance between jetting reliability and thermal and / or radiation absorption efficiency in the core fusing agent.

[0102] Base fusing agent

[0103] In some instances, the flux is a base flux, and the electromagnetic radiation absorber is a plasmon resonance absorber with absorption at wavelengths from 800 nm to 4000 nm and transparency at wavelengths from 400 nm to 780 nm. Therefore, the absorption of this energy absorber is a result of the plasmon resonance effect. Electrons associated with the atoms of the energy absorber can be collectively excited by radiation, resulting in collective oscillations of the electrons. The wavelength at which these electrons can be collectively excited and oscillated depends on the number of electrons present in the energy absorber particles, which in turn depends on the size of the energy absorber particles. The energy of the electrons in the collectively oscillating particles is low enough that extremely small particles (e.g., 1–100 nm) can absorb radiation with wavelengths several times (e.g., 8 to 800 times or more) larger than the particle size. The use of these particles makes the base flux inkjet-electro-selective and electromagnetically selective (e.g., with absorption at wavelengths from 800 nm to 4000 nm and transparency at wavelengths from 400 nm to 780 nm).

[0104] In one example, the energy absorber of the underlayer flux has an average particle size (e.g., volume-weighted average diameter) greater than 0 nm to less than 220 nm. In another example, the energy absorber has an average particle size greater than 0 nm to 120 nm. In yet another example, the energy absorber has an average particle size of approximately 10 nm to approximately 200 nm.

[0105] In one instance, the energy absorber in this primer is an inorganic pigment. Examples of suitable inorganic pigments include lanthanum hexaboride (LaB6) and tungsten bronze (A). x WO3), indium tin oxide (In2O3:SnO2, ITO), antimony tin oxide (Sb2O3:SnO2, ATO), titanium nitride (TiN), aluminum zinc oxide (AZO), ruthenium oxide (RuO2), silver (Ag), gold (Au), platinum (Pt), ferropyroxene (A x Fe y Si₂O₆, where A is Ca or Mg, x = 1.5-1.9 and y = 0.1-0.5), and modified iron phosphate (A x Fe y PO4), modified copper phosphate (A) x Cu y PO z ) and modified copper pyrophosphate (A x Cu y P2O7). Tungsten bronze can be alkali metal-doped tungsten oxide. Suitable alkali metal dopants (i.e., A...) xExamples of WO3 (A) can be cesium, sodium, potassium, or rubidium. In one example, alkali metal-doped tungsten oxide can be doped in an amount greater than 0 mol% to about 0.33 mol% based on the total mol% of alkali metal-doped tungsten oxide. Suitable modified iron phosphate (A) x Fe y PO4 can include copper ferric phosphate (A = Cu, x = 0.1–0.5 and y = 0.5–0.9), magnesium ferric phosphate (A = Mg, x = 0.1–0.5 and y = 0.5–0.9), and zinc ferric phosphate (A = Zn, x = 0.1–0.5 and y = 0.5–0.9). For modified ferric phosphate, it is important to understand that the amount of phosphate can be varied based on the charge balance with the cations. Suitable modified copper pyrophosphate (A... x Cu y P2O7 includes copper iron pyrophosphate (A = Fe, x = 0-2 and y = 0-2), copper magnesium pyrophosphate (A = Mg, x = 0-2 and y = 0-2), and copper zinc pyrophosphate (A = Zn, x = 0-2 and y = 0-2). Combinations of inorganic pigments can also be used.

[0106] The amount of energy absorber present in the undercoat flux is greater than 0% by weight of active material to about 40% by weight of active material based on the total weight of the undercoat flux. In other instances, the amount of energy absorber in the undercoat flux is about 0.3% by weight of active material to 30% by weight of active material, about 1% by weight of active material to about 20% by weight of active material, about 1.0% by weight of active material to about 10.0% by weight of active material, or greater than 4.0% by weight of active material to about 15.0% by weight of active material. It is believed that these energy absorber loadings provide a balance between injection reliability and thermal and / or radiation absorption efficiency in the undercoat flux.

[0107] In some cases, the energy absorber in a base coat of the filler can be dispersed using a dispersant. Therefore, the dispersant helps to evenly distribute the energy absorber throughout the base coat. Examples of suitable dispersants include polymeric or small molecule dispersants, charged groups attached to the surface of the energy absorber, or other suitable dispersants. Some specific examples of suitable dispersants include water-soluble acrylic polymers (e.g., those available from Lubrizol). K7028), water-soluble styrene-acrylic acid copolymer / resin (e.g., available from BASF Corp.) 296、 671. 678、 680 683、 690, etc.), high molecular weight block copolymers with pigment affinity groups (e.g., those available from BYK Additives and Instruments). -190) or water-soluble styrene-maleic anhydride copolymer / resin.

[0108] Whether a single dispersant or a combination of dispersants is used, the total amount of the one or more dispersants in the primer fusing agent can be about 10 wt.% to about 200 wt.% of the energy absorber in the primer fusing agent.

[0109] Silane coupling agents can also be added to the primer fusing agent to aid in bonding organic materials (e.g., dispersants) and inorganic materials (e.g., pigments). Examples of suitable silane coupling agents include Momentive Silquest® A series.

[0110] Whether a single silane coupling agent or a combination of silane coupling agents is used, the total amount of the one or more silane coupling agents in the primer fusing agent can be about 0.1 wt.% to about 50 wt.% of the energy absorber in the primer fusing agent. In one example, the total amount of the one or more silane coupling agents in the primer fusing agent is about 1 wt.% to about 30 wt.% of the energy absorber. In another example, the total amount of the one or more silane coupling agents in the primer fusing agent is about 2.5 wt.% to about 25 wt.% of the energy absorber.

[0111] One example of the primer fusing agent includes cesium tungsten oxide (CTO) nanoparticles as the energy absorber. The CTO nanoparticles have the formula Cs x WO3, where 0 < x < 1. The cesium tungsten oxide nanoparticles can impart a light blue color to the primer fusing agent. The intensity of the color can depend at least in part on the amount of CTO nanoparticles in the primer fusing agent. When it is desired to form a white outer layer on the 3D object, less CTO nanoparticles can be used in the primer fusing agent to achieve a white color. In one example, the CTO nanoparticles can be present in the primer fusing agent in an amount of about 1 wt.% to about 20 wt.% (based on the total weight of the primer fusing agent).

[0112] The average particle size (e.g., volume weighted average diameter) of the CTO nanoparticles can be about 1 nm to about 40 nm. In some examples, the average particle size of the CTO nanoparticles can be about 1 nm to about 15 nm or about 1 nm to about 10 nm. The upper end of the particle size range (e.g., about 30 nm to about 40 nm) can be less desirable because these particles can be more difficult to stabilize.

[0113] This example of a primer fusing agent can also include a zwitterionic stabilizer. The zwitterionic stabilizer can improve the stabilization of this example of a primer fusing agent. Although the zwitterionic stabilizer has an overall neutral charge, at least one region of the molecule has a positive charge (e.g., an amino group) and at least one other region of the molecule has a negative charge. The CTO nanoparticles can have a slight negative charge. The zwitterionic stabilizer molecule can orient around the slightly negatively charged CTO nanoparticles with the positively charged region of the zwitterionic stabilizer molecule closest to the CTO nanoparticles and the negatively charged region of the zwitterionic stabilizer molecule farthest from the CTO nanoparticles. Subsequently, the negative charge of the negatively charged region of the zwitterionic stabilizer molecule can push the CTO nanoparticles away from each other. The zwitterionic stabilizer molecule can form a protective layer around the CTO nanoparticles and prevent them from directly contacting each other and / or increase the distance between the particle surfaces (e.g., by about 1 nm to about 2 nm). Thus, the zwitterionic stabilizer can prevent the CTO nanoparticles from agglomerating and / or settling in the primer fusing agent.

[0114] Examples of suitable zwitterionic stabilizers include C2 to C8 betaines, C2 to C8 amino carboxylic acids having a solubility of at least 10 grams in 100 grams of water, taurine, and combinations thereof. Examples of C2 to C8 amino carboxylic acids include beta-alanine, gamma-aminobutyric acid, glycine, and combinations thereof.

[0115] The zwitterionic stabilizer can be present in the primer fusing agent in an amount of about 2 wt% to about 35 wt% (based on the total weight of the primer fusing agent). When the zwitterionic stabilizer is a C2 to C8 betaine, the C2 to C8 betaine can be present in an amount of about 8 wt% to about 35 wt% of the total weight of the primer fusing agent. When the zwitterionic stabilizer is a C2 to C8 amino carboxylic acid, the C2 to C8 amino carboxylic acid can be present in an amount of about 2 wt% to about 20 wt% of the total weight of the primer fusing agent. When the zwitterionic stabilizer is taurine, the taurine can be present in an amount of about 2 wt% to about 35 wt% of the total weight of the primer fusing agent.

[0116] In this example, the weight ratio of CTO nanoparticles to zwitterionic stabilizer can be 1 : 10 to 10: 1; or the weight ratio of CTO nanoparticles to zwitterionic stabilizer can be 1 : 1.

[0117] Carrier for fusing agent

[0118] Any of the examples of fusing agents (core fusing agents or priming fusing agents) include a liquid carrier. A fusing agent carrier or "FA carrier" can refer to a liquid in which an energy absorber is dispersed or dissolved to form the corresponding fusing agent. A wide variety of FA carriers can be used in fusing agents, including aqueous and non-aqueous carriers. In some examples, the FA carrier can include only water or only a non-aqueous solvent without other components. In other examples, the FA carrier can include other components, depending in part on the applicator used to dispense the fusing agent. Examples of other suitable fusing agent components include one or more co-solvents, one or more surfactants, one or more antimicrobial agents, one or more anti-kogation agents, one or more chelating agents, and / or one or more wetting agents.

[0119] It is to be understood that any of the one or more co-solvents and / or one or more surfactants described herein for the antioxidant formulation can be used in any of the examples of fusing agents in any of the amounts provided, just with the percentages being relative to the total weight of the fusing agent.

[0120] The FA carrier can also include one or more antimicrobial agents. Antimicrobial agents are also known as biocides and / or fungicides. Examples of suitable antimicrobial agents include UCARCIDE® (The Dow Chemical Company), TM or KORDEK® (Thor Chemicals), TM or ROCIMA® (Arch Chemicals), TM BIOBAN® (The Dow Chemical Company), the DOWFAX® series of surfactants (The Dow Chemical Company), B20 and B30 (BASF), M20 and M30 (BASF), MBL (a blend of 2-methyl-4-isothiazolin-3-one (MIT), 1,2-benzisothiazolin-3-one (BIT), and Bronopol) (Thor Chemicals), AXIDE® (Planet Chemical), TM NIPACIDE® (Clariant), TM the trademark KATHON® (E.I. du Pont de Nemours and Company), TM a blend of 5-chloro-2-methyl-4-isothiazolin-3-one (CIT or CMIT) and MIT (The Dow Chemical Company), and combinations thereof.

[0121] In one example, the total amount of the one or more antimicrobial agents in the fusing agent is from about 0.01 wt. % active to about 0.05 wt. % active (based on the total weight of the fusing agent). In another example, the total amount of the one or more antimicrobial agents in the fusing agent is about 0.04 wt. % active (based on the total weight of the fusing agent).

[0122] The FA carrier can also include one or more anti-kogation agents to be jetted using thermal inkjet printing. Kogation refers to the deposition of dried printing liquid (e.g., fusing agent) on the heating elements of a thermal inkjet printhead. The one or more anti-kogation agents are included to help prevent the build-up of kogation.

[0123] Examples of suitable anti-kogation agents include Oily Polyoxethylene (3) Ether-Phosphate (available as CRODAFOS® O3A or CRODAFOS® N-3A) or Dextran 500k. Other suitable examples of anti-kogation agents include CRODAFOS® HCE (phosphate ester from Croda Int.), CRODAFOS® O10A (oily polyoxethylene (10) ether-phosphate from Croda Int.), and TM CRODAS® O3A or CRODAFOS® N-3A) or Dextran 500k. Other suitable examples of anti-kogation agents include CRODAFOS® HCE (phosphate ester from Croda Int.), CRODAFOS® O10A (oily polyoxethylene (10) ether-phosphate from Croda Int.), and TM CRODAS® O3A or CRODAFOS® N-3A) or Dextran 500k. Other suitable examples of anti-kogation agents include CRODAFOS® HCE (phosphate ester from Croda Int.), CRODAFOS® O10A (oily polyoxethylene (10) ether-phosphate from Croda Int.), and TM CRODAS® HCE (phosphate ester from Croda Int.), CRODAFOS® O10A (oily polyoxethylene (10) ether-phosphate from Croda Int.), and CRODAS® HCE (phosphate ester from Croda Int.), CRODAFOS® O10A (oily polyoxethylene (10) ether-phosphate from Croda Int.), and CRODAS® HCE (phosphate ester from Croda Int.), CRODAFOS® O10A (oily polyoxethylene (10) ether-phosphate from Croda Int.), and

[0124] The anti-kogation agent can be present in the fusing agent in an amount of from about 0.1 wt. % active to about 1.5 wt. % active based on the total weight of the fusing agent. In one example, the anti-kogation agent is present in an amount of about 0.5 wt. % active based on the total weight of the fusing agent.

[0125] A chelating agent (or sequestering agent) can be included in the aqueous liquid carrier of the fusing agent to eliminate the deleterious effects of heavy metal impurities. In one example, the chelating agent is selected from the group consisting of trisodium methylglycinediacetic acid salt; disodium 4,5-dihydroxy-1,3-benzenedisulfonate monohydrate; ethylenediaminetetraacetic acid (EDTA); potassium hexamethylenedi-amine tetra(methylene phosphonate); and combinations thereof. Trisodium methylglycinediacetic acid salt (Na3MGDA) is commercially available as TIRON® M from BASF Corp. Disodium 4,5-dihydroxy-1,3-benzenedisulfonate monohydrate is commercially available as TIRON® 4M from BASF Corp. Ethylenediaminetetraacetic acid (EDTA) is commercially available as TM TIRON® 4M from BASF Corp. Ethylenediaminetetraacetic acid (EDTA) is commercially available as TIRON® 2054 from Italmatch Chemicals.

[0126] Whether a single chelant is used or a combination of chelants is used, the total amount of the one or more chelants in the fusing agent can be greater than 0 wt. % active to about 0.5 wt. % active, based on the total weight of the fusing agent. In one example, the chelant is present in an amount of about 0.05 wt. % active to about 0.2 wt. % active, based on the total weight of the fusing agent. In another example, the one or more chelants are present in the fusing agent in an amount of about 0.05 wt. % active, based on the total weight of the fusing agent.

[0127] The FA carrier can also include one or more wetting agents. One example of a suitable wetting agent is an ethoxylated glycerol having the following formula:

[0128]

[0129] where the sum of a+b+c is about 5 to about 60, or in other examples, about 20 to about 30. One example of an ethoxylated glycerol is EG-1 (LEG-1, glycerol polyoxoethylene (26) ether, a+b+c = 26, available from Lipo Chemicals).

[0130] In one example, the total amount of the one or more wetting agents present in the fusing agent is about 3 wt. % active to about 10 wt. % active, based on the total weight of the fusing agent.

[0131] The balance of the one or more fusing agents is water (e.g., deionized water, purified water, etc.), which can vary depending on the other components in the one or more fusing agents, as described herein.

[0132] Refining agent

[0133] Some examples of multi-fluid kits and / or 3D printing kits include a refining agent. The refining agent can include a surfactant, a co-solvent, and a balance of water. In some examples, the refining agent consists of these components, and no other components. In other examples, the refining agent can further include a colorant. In yet other examples, the refining agent consists of a colorant, a surfactant, a co-solvent, and a balance of water, and no other components. In still other examples, the refining agent can further include additional components, such as one or more anti-foaming agents, one or more antimicrobial agents, and / or one or more chelants (each described above with reference to the fusing agent).

[0134] The one or more surfactants that can be used in the refining agent include any of the surfactants listed herein with respect to the antioxidant formulation. The total amount of the one or more surfactants in the refining agent can be about 0.10 wt. % to about 5 wt. % of the total weight of the refining agent.

[0135] One or more co-solvents that can be used in the detailing agent include any of the co-solvents listed above with respect to the antioxidant formulation. The total amount of one or more co-solvents in the detailing agent can be from about 1 wt% to about 65 wt% of the total weight of the detailing agent.

[0136] In some examples, the detailing agent does not include a colorant. In these examples, the detailing agent can be colorless. As used herein, "colorless" means that the detailing agent is non-colored and does not include a colorant.

[0137] When the detailing agent includes a colorant, the colorant can be a dye of any color that has substantially no absorbance in the range of 650 nm to 2500 nm. "Substantially no absorbance" means that the dye does not absorb radiation having a wavelength of 650 nm to 2500 nm, or that the dye absorbs less than 10% of radiation having a wavelength of 650 nm to 2500 nm. The dye can also be capable of absorbing radiation having a wavelength of 650 nm or less. Thus, the dye absorbs at least some wavelengths within the visible spectrum, but absorbs little or none of the wavelengths within the near infrared spectrum. This is different from the active (energy absorbing) material in the fusing agent, which absorbs wavelengths within the near infrared spectrum. Thus, the colorant in the detailing agent does not substantially absorb the fusing radiation, thereby not initiating melting and fusing (coalescing) of the build material composition with which it is in contact when the build material layer is exposed to energy.

[0138] When the detailing agent is applied to the edge of a colored part, it can be desirable to add color to the detailing agent. The color in the detailing agent can be desirable when used at the edge of a part because some colorants can become embedded in the polymer build material that is fused / coalesced at the edge. Thus, in some examples, the dye in the detailing agent can be selected so that its color matches the color of the active material in the fusing agent. For example, the dye can be any azo dye with a sodium or potassium counterion or any diazo (i.e., disazo) dye with a sodium or potassium counterion, where the color of the azo dye matches the color of the fusing agent.

[0139] In one example, the dye is a black dye. Some examples of black dyes include azo dyes with a sodium or potassium counterion and diazo (i.e., disazo) dyes with a sodium or potassium counterion. Examples of azo and diazo dyes can include tetrasodium (6Z)-4-acetamido-5-oxo-6-[[7-sulfonato-4-(4-sulfonatophenyl)azo-1-naphthyl]hydrazono]naphthalene-1,7-disulfonate with the following chemical structure: (available as Food Black 1); tetrasodium 6-amino-4-hydroxy-3-[[7-sulfonato-4-[(4-sulfonatophenyl)azo]-1-naphthyl]azo]naphthalene-2,7-disulfonate with the following chemical structure: (available as Food Black 2); (6E)-4-amino-5-oxo-3-[[4-(2-sulfonatooxyethylsulfonyl)phenyl]diazene]-6-[[4-(2-sulfonatooxyethylsulfonyl)phenyl]hydrazinylidene]naphthalene-2,7-disulfonic acid tetrasodium salt having the following chemical structure: (available as Reactive Black 31); (6E)-4-amino-5-oxo-3-[[4-(2-sulfonatooxyethylsulfonyl)phenyl]diazene]-6-[[4-(2-sulfonatooxyethylsulfonyl)phenyl]hydrazinylidene]naphthalene-2,7-disulfonic acid tetrasodium salt having the following chemical structure: and combinations thereof. Other commercially available examples of dyes used in the detailing agent include multipurpose black azo dye-based liquids such as Fast Black 1 (available from Fujifilm Holdings), and black azo dye-based liquids with enhanced water fastness such as Fast Black 2 (available from Fujifilm Holdings).

[0140] In some cases, the colorant in the detailing agent can further include another dye in addition to the black dye. In one example, the other dye can be a cyan dye used in combination with any of the dyes disclosed herein. The other dye can also have substantially no absorbance above 650 nm. The other dye can be any colored dye that helps improve the shade and color uniformity of the final 3D part.

[0141] Some examples of the other dye include salts, such as sodium, ammonium, or potassium salts. Some specific examples include ethyl-[4-[[4-[ethyl-[(3-sulfophenyl)methyl]amino]phenyl]-(2-sulfophenyl)ethylidene]-1- cyclohex-2,5-dienyl]-[(3-sulfophenyl)methyl]azanium having the following chemical structure:

[0142]

[0143] (available as Acid Blue 9, where the counterion can alternatively be a sodium counterion or a potassium counterion); sodium 4-[(E)-{4-[benzyl(ethyl)amino]phenyl}{(4E)-4-[benzyl(ethyl)imino]cyclohexa-2,5-dien-1- yl}methyl]benzene-1,3-disulfonate having the following chemical structure:

[0144] (available as Acid Blue 7); and phthalocyanine having the following chemical structure: (available as Direct Blue 199); and combinations thereof.

[0145] In one example of the detailing agent, the dye can be present in an amount of about 1 wt% to about 3 wt% based on the total weight of the detailing agent. In another example of the detailing agent comprising a combination of dyes, one dye (e.g., a black dye) is present in an amount of about 1.50 wt% to about 1.75 wt% based on the total weight of the detailing agent, and another dye (e.g., a cyan dye) is present in an amount of about 0.25 wt% to about 0.50 wt% based on the total weight of the detailing agent.

[0146] The balance of the detailing agent is water. Thus, the amount of water can vary with the amount of other components included.

[0147] Coloring agent

[0148] Some examples of the multi-fluid kit and / or 3D printing kit include a coloring agent. The coloring agent can include a colorant, a co-solvent, and a balance of water. In some examples, the coloring agent consists of these components, and no other components. In other examples, the coloring agent can further include a binder (e.g., an acrylic latex binder, which can be a copolymer of any two or more of styrene, acrylic acid, methacrylic acid, methyl methacrylate, ethyl methacrylate, and butyl methacrylate) and / or a buffer. In still other examples, the coloring agent can further include additional components, such as one or more dispersants, one or more wetting agents, one or more surfactants, one or more anti- scaling agents, one or more antimicrobial agents, and / or one or more chelating agents (each described herein with reference to the antioxidant formulation and / or fusing agent).

[0149] The coloring agent can be a black agent, a cyan agent, a magenta agent, or a yellow agent. Thus, the colorant can be a black colorant, a cyan colorant, a magenta colorant, a yellow colorant, or a combination of colorants that together achieve black, cyan, magenta, or yellow.

[0150] In some instances, the colorant of the coloring agent can be transparent to infrared wavelengths. In other instances, the colorant of the coloring agent can not be completely transparent to infrared wavelengths, but does not absorb sufficient radiation to sufficiently heat a build material composition in contact therewith. In one example, the colorant absorbs less than 10% of radiation having a wavelength of 650 nm to 2500 nm. In another example, the colorant absorbs less than 20% of radiation having a wavelength of 650 nm to 4000 nm.

[0151] The colorant of the colorant agent can also absorb radiation at wavelengths of 650 nm or less. Thus, the colorant absorbs at least some wavelengths within the visible spectrum, but absorbs little or none of the wavelengths within the near infrared spectrum. This is different from at least some examples of energy absorbers in fusing agents, which absorb wavelengths within the near infrared spectrum and / or the infrared spectrum. Thus, the colorant in the colorant agent will not significantly absorb the fusing radiation, thereby not initiating coalescence / fusing of the build material composition with which it is in contact when the build material composition is exposed to energy.

[0152] Examples of IR transparent colorants include Acid Yellow 23 (AY 23), AY 17, Acid Red 52 (AR 52), AR 289, and Reactive Red 180 (RR 180). Examples of colorants that absorb some visible wavelengths and some IR wavelengths include cyan colorants such as Direct Blue 199 (DB 199) and Pigment Blue 15:3 (PB 15:3).

[0153] In other examples, the colorant can be any azo dye having a sodium or potassium counterion or any diazo (i.e., disazo) dye having a sodium or potassium counterion, such as those described herein for detailing agents.

[0154] Examples of pigment-based colorant agents can include from about 1 wt% to about 10 wt% of one or more pigments, from about 10 wt% to about 30 wt% of one or more co-solvents, from about 1 wt% to about 10 wt% of one or more dispersants, from about 0.1 wt% to about 5 wt% of one or more binders, from 0.01 wt% to about 1 wt% of one or more anti- fouling agents, from about 0.05 wt% to about 0.1 wt% of one or more antimicrobial agents, and a balance of water. Examples of dye-based colorant agents can include from about 1 wt% to about 7 wt% of one or more dyes, from about 10 wt% to about 30 wt% of one or more co-solvents, from about 1 wt% to about 7 wt% of one or more dispersants, from about 0.05 wt% to about 0.1 wt% of one or more antimicrobial agents, from 0.05 wt% to about 0.1 wt% of one or more chelating agents, from about 0.005 wt% to about 0.2 wt% of one or more buffering agents, and a balance of water.

[0155] Some examples of colorant reagents include a set of cyan, magenta, and yellow reagents such as C1893A (cyan), C1984A (magenta), and C1985A (yellow); or C4801A (cyan), C4802A (magenta), and C4803A (yellow); all available from HP Inc. Other commercially available colorant reagents 18 include C9384A (printhead HP 72), C9383A (printhead HP 72), C4901A (printhead HP 940), and C4900A (printhead HP 940).

[0156] Build material composition

[0157] The build material composition comprises a polymeric build material. Examples of suitable polymeric materials include polyamides (PA) (e.g., PA 11 / nylon 11, PA 12 / nylon 12, PA 6 / nylon 6, PA 8 / nylon 8, PA 9 / nylon 9, PA 66 / nylon 66, PA 612 / nylon 612, PA 812 / nylon 812, PA 912 / nylon 912, etc.), thermoplastic polyamides (TPA), thermoplastic polyurethanes (TPU), styrene block copolymers (TPS), thermoplastic polyolefin elastomers (TPO), thermoplastic vulcanizates (TPV), thermoplastic copolyesters (TPC), polyether block amides (PEBA), and combinations thereof.

[0158] In some examples, the polymeric build material can be in the form of a powder. In other examples, the polymeric build material can be in the form of a powdered material that includes, for example, short fibers having a length that is greater than their width. In some examples, the powder or powdered material can be formed from or can include short fibers that, for example, can have been cut from a long strand or thread of material into a short length.

[0159] The polymeric build material can be composed of particles of similar size or particles of different sizes. In one example, the polymeric build material has an average particle size of about 2 pm to about 225 pm. In another example, the polymeric build material has an average particle size of about 10 pm to about 130 pm. As noted above, the term “average particle size” as used herein can refer to the number- or volume-weighted average diameter of a distribution of particles.

[0160] When the polymer build material is a polyamide, the polymer can have a broad processing window of greater than 5°C, which can be defined by the temperature range between the melting point and the recrystallization temperature. In one example, the polymer can have a melting point of about 50°C to about 300°C. As other examples, the polymer can have a melting point of about 155°C to about 225°C, about 155°C to about 215°C, about 160°C to about 200°C, about 170°C to about 190°C, or about 182°C to about 189°C. As yet other examples, the polymer can be a polyamide having a melting point of about 180°C.

[0161] When the polymer build material is a thermoplastic elastomer, the thermoplastic elastomer can have a melting range of about 130°C to about 250°C. In some examples (e.g., when the thermoplastic elastomer is a polyether block amide), the thermoplastic elastomer can have a melting range of about 130°C to about 175°C. In other examples (e.g., when the thermoplastic elastomer is a thermoplastic polyurethane), the thermoplastic elastomer can have a melting range of about 130°C to about 180°C or a melting range of about 175°C to about 210°C.

[0162] In some examples, the polymer build material does not substantially absorb radiation having a wavelength in the range of 300 nm to 1400 nm. The phrase "does not substantially absorb" means that the polymer build material has an absorption of 25% or less (e.g., 20%, 10%, 5%, etc.) at the particular wavelength.

[0163] In some examples, in addition to the polymer build material, the build material composition can include an antioxidant, a whitening agent, an antistatic agent, a flow aid, or a combination thereof. While several examples of these additives are provided, it is understood that these additives are selected so as to be thermally stable (i.e., will not decompose) at the 3D printing temperature.

[0164] One or more antioxidants can be added to the build material composition to prevent or slow the decrease in molecular weight of the polymer build material and / or can prevent or slow discoloration (e.g., yellowing) of the polymer build material by preventing or slowing oxidation of the polymer build material. In some examples, the polymer material can discolor upon reaction with oxygen, and this discoloration can result in discoloration of the build material composition. The antioxidant can be selected to minimize discoloration. In some examples, the antioxidant can be a free radical scavenger. In these examples, the antioxidant can include 1098 (benzenepropanamide, N,N'-1,6-hexanediylbis(3,5-bis(1,1-dimethylethyl)-4- hydroxy)), 254 (a mixture of triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl), polyvinyl alcohol, and deionized water) and / or other hindered phenols. In other examples, the antioxidant can include phosphites and / or organic sulfides (e.g., thioesters). The antioxidant can be in the form of a fine particle (e.g., average particle size of 5 pm or less) dry blended with the polymeric build material 16. In one example, the antioxidant can be included in the build material composition in an amount of about 0.01 wt% to about 5 wt%, based on the total weight of the build material composition. In other examples, the antioxidant can be included in the build material composition in an amount of about 0.01 wt% to about 2 wt% or about 0.2 wt% to about 1 wt%, based on the total weight of the build material composition.

[0165] One or more whitening agents can be added to the build material composition to improve visibility. Examples of suitable whitening agents include titanium dioxide (Ti02), zinc oxide (ZnO), calcium carbonate (CaC03), zirconium dioxide (Zr02), aluminum oxide (AI2O3), silicon dioxide (Si02), boron nitride (BN), and combinations thereof. In some examples, stilbene derivatives can be used as whitening agents and brightening agents. In these examples, one or more temperatures of the 3D printing process can be selected such that the stilbene derivatives remain stable (i.e., the 3D printing temperatures do not thermally decompose the stilbene derivatives). In one example, any of the examples of whitening agents can be included in the build material composition in an amount of greater than 0 wt% to about 10 wt%, based on the total weight of the build material composition.

[0166] One or more antistatic agents can be added to the build material composition to inhibit tribocharging. Examples of suitable antistatic agents include aliphatic amines (which can be ethoxylated), aliphatic amides, quaternary ammonium salts (e.g., behenyltrimethylammonium chloride or cocamidopropyl betaine), esters of phosphoric acid, polyethylene glycol esters, or polyols. Some suitable commercially available antistatic agents include FA 38 (a natural-based ethoxylated alkyl amine), FE2 (a fatty acid ester), and HS1 (an alkyl sulfonate), each of which can be obtained from Clariant Int. Ltd. In one example, the antistatic agent is added in an amount of greater than 0 wt% to less than 5 wt%, based on the total weight of the build material composition.

[0167] One or more flow aids can be added to improve the flowability of the build material composition. Flow aids can be particularly beneficial when the average particle size of the build material composition is less than 25 microns. Flow aids improve the flowability of the build material composition by reducing friction, lateral resistance, and the accumulation of triboelectric charge (by increasing the electrical conductivity of the particles). Examples of suitable flow aids include aluminium oxide (Al203), tribasic calcium phosphate (E341), powdered cellulose (E460(ii)), magnesium stearate (E470b), sodium bicarbonate (E500), sodium ferrocyanide (E535), potassium ferrocyanide (E536), calcium ferrocyanide (E538), bone phosphate (E542), sodium silicate (E550), silicon dioxide (E551), calcium silicate (E552), magnesium trisilicate (E553a), talc (E553b), sodium aluminosilicate (E554), potassium aluminium silicate (E555), calcium aluminosilicate (E556), bentonite (E558), aluminium silicate (E559), stearic acid (E570), and polydimethylsiloxane (E900). In one example, the flow aid is added in an amount of greater than 0 wt% to less than 5 wt% based on the total weight of the build material composition.

[0168] Printing method and method of use

[0169] Reference Figures 1 to 7 Different examples of 3D printing methods are shown and described.

[0170] Before any of the examples of the method are performed, it is to be understood that the controller has access to data stored in the data store regarding the 3D part / object to be printed. For example, the controller can determine the number of layers of build material composition to be formed, the location at which any reagent is to be deposited on each respective layer, and the like.

[0171] Printing with antioxidant formulation and one fusing agent

[0172] Reference is now made to Figure 1 and Figure 2 depicting one example of a method 100 utilizing an antioxidant formulation and a fusing agent.

[0173] Figure 1 The method 100 shown in includes applying a polymeric build material composition to form a build material layer (reference numeral 102); selectively applying a fusing agent on at least a portion of the build material layer based on a 3D object model (reference numeral 104); selectively applying an antioxidant formulation on at least the portion of the build material layer based on the 3D object model, wherein the antioxidant formulation includes water and an antioxidant blend consisting of a primary antioxidant and a secondary antioxidant (reference numeral 106); and exposing the build material layer to electromagnetic radiation to coalesce at least the portion to form a layer of the 3D object (reference numeral 108).

[0174] The method 100 is schematically shown in Figure 2 The method 100 is schematically shown in Figure 2 In some examples, a layer 10 of the polymeric build material composition 12 is applied on the build area platform 14. A printing system can be used to apply the polymeric build material composition 12. The printing system can include the build area platform 14, a build material supply 16 containing the build material composition 12, and a build material distributor 18.

[0175] The build area platform 14 receives the polymeric build material composition 12 from the build material supply 16. The build area platform 14 can be moved in the direction shown by arrow 20, for example along the z-axis, so that the polymeric build material composition 12 can be delivered onto the build area platform 14 or onto a previously formed layer. In one example, the build area platform 14 can be programmed to advance (e.g., advance downward) enough so that the build material distributor 18 can push the polymeric build material composition 12 onto the build area platform 14 to form a substantially uniform layer 10 of the build material composition 12 thereon when the polymeric build material composition 12 is to be delivered. The build area platform 14 can also return to its original position, for example when a new part is to be built.

[0176] The build material supply 16 can be a container, bed, or other surface that positions the build material composition 12 between the build material distributor 18 and the build area platform 14. The build material supply 16 can include a heater to heat the polymeric build material composition 12 to a supply temperature of about 25 °C to about 150 °C. In these examples, the supply temperature can depend in part on the polymeric build material composition 12 used and / or the 3D printer used. Thus, the ranges provided are one example, and higher or lower temperatures can be used.

[0177] The build material distributor 18 can be moved above the build material supply 16 and across the build area platform 14 in the direction shown by arrow 22, for example along the y-axis, to spread the layer 10 of the polymeric build material composition 12 on the build area platform 14. The build material distributor 18 can also return to a position adjacent to the build material supply 16 after spreading the polymeric build material composition 12. The build material distributor 18 can be a blade (e.g., a doctor blade), a roller, a combination of a roller and a blade, and / or any other device that can spread the polymeric build material composition 12 on the build area platform 14. For example, the build material distributor 18 can be counter-rotating rollers. In some examples, the build material supply 16 or a portion of the build material supply 16 can be moved with the build material distributor 18 so that the polymeric build material composition 12 is continuously delivered to the build area platform 14 rather than being supplied from a single location on the side of the printing system as depicted in Figure 2 The build material supply 16 can be a container, bed, or other surface that positions the build material composition 12 between the build material distributor 18 and the build area platform 14. The build material supply 16 can include a heater to heat the polymeric build material composition 12 to a supply temperature of about 25 °C to about 150 °C. In these examples, the supply temperature can depend in part on the polymeric build material composition 12 used and / or the 3D printer used. Thus, the ranges provided are one example, and higher or lower temperatures can be used.

[0178] The build material supply 16 can supply the polymeric build material composition 12 to a location to make it ready for spreading onto the build area platform 14. The build material spreader 18 can spread the supplied polymeric build material composition 12 onto the build area platform 14. A controller (not shown) can process "control build material supply" data and, in response, control the build material supply 16 to place the particles of the polymeric build material composition 12 as appropriate, and can process "control spreader" data and, in response, control the build material spreader 18 to spread the polymeric build material composition 12 on the build area platform 14 to form a layer 10 of the polymeric build material composition 12 thereon. In Figure 2 In the example shown in FIG. 1, a layer 10 of the polymeric build material composition 12 has been formed on the build area platform 14.

[0179] The layer 10 has a substantially uniform thickness on the build area platform 14. In one example, the thickness of the build material layer 10 is about 50 μιη to about 120 μιη. In another example, the thickness of the build material layer 26 is about 30 μιη to about 300 μιη. It is to be understood that thinner or thicker layers can also be used. For example, the thickness of the build material layer 10 can be about 20 μιη to about 500 μιη. For finer part definition, the layer thickness can be as small as about 2x (i.e., 2 times) the average diameter of the build material composition particles. In some examples, the layer thickness can be about 1.2x the average diameter of the build material composition particles.

[0180] After the polymeric build material composition 12 has been applied and before further processing, the build material layer 10 can be exposed to heat. In one example, the heat temperature can be below the melting point or melting range of the polymeric material of the polymeric build material composition 12. As an example, the pre-heat temperature can be about 5 °C to about 50 °C below the lowest temperature of the melting point or melting range of the polymeric material. In one example, the pre-heat temperature is about 50 °C to about 205 °C. In another example, the pre-heat temperature is about 100 °C to about 190 °C. It is to be understood that the pre-heat temperature can depend in part on the polymeric build material composition 12 used. Thus, the ranges provided are some examples, and higher or lower temperatures can be used.

[0181] Pre-heating the layer 10 can be accomplished by using any suitable heat source that exposes all of the polymeric build material composition 12 in the layer 10 to heat. Examples of heat sources include a thermal heat source (e.g., a heater (not shown) integrated into the build area platform 14 (which can include side walls)) or a radiation source 24.

[0182] After the layer 10 is formed and in some cases pre-heated, one or more fusing agents 26 or 26' are selectively applied on at least a portion of the polymeric build material composition 12 in the layer 10 to form a patterned portion 28.

[0183] To form a layer 30 of a 3D object, at least a portion of the layer 10 of build material composition 12 (e.g., the patterned portion 28) is patterned with a fusing agent 26, 26'. Either fusing agent 26 or 26' can be used. When it is desired to form a layer 30 of a 3D object that is white, colored, or slightly tinted, the build material composition 12 can be patterned with a base fusing agent 26'. The base fusing agent 26' is transparent or slightly tinted, and the resulting layer 30 of a 3D object can exhibit a white color or the color of the polymeric build material composition 12. When it is desired to form a layer 30 of a 3D object that is darker or black, the core fusing agent 26 can be used. The core fusing agent 26 is dark or black, and the resulting layer 30 of a 3D object can exhibit a gray, black, or another dark color. In other examples of the method (e.g., the method 200 shown in Figure 3 and Figure 4 The two fusing agents 26, 26' can be used to pattern different portions of a single build material layer 10, which will be further described with reference to Figure 3 and Figure 4 The two fusing agents 26, 26' can be used to pattern different portions of a single build material layer 10, which will be further described with reference to Figure 6 The two fusing agents 26, 26' can be used to pattern different portions of a single build material layer 10, which will be further described with reference to

[0184] The volume of fusing agent 26, 26' applied per unit of polymeric build material composition 12 in the patterned portion 28 can be sufficient to absorb and convert enough electromagnetic radiation to cause the polymeric build material composition 24 in the patterned portion 28 to coalesce / fuse. The volume of fusing agent 26, 26' applied per unit of polymeric build material composition 12 can depend at least in part on the energy absorber used, the energy absorber loading in the fusing agent 26, 26', and the polymeric build material composition 12 used.

[0185] To reduce thermal degradation of the polymeric build material composition 12, an antioxidant formulation 34 can be applied to all or a portion of the build material layer 10. In some examples, the antioxidant formulation 34 can be applied to the patterned portion 28. Applying the antioxidant formulation 34 in this portion 28 helps to reduce thermal degradation of the layer 30 of a 3D object, and thereby improves the quality of the layer 30 of a 3D object.

[0186] The antioxidant formulation 34 can provide a cooling effect, and thereby control the ratio of the antioxidant formulation 34 to the fusing agent 26 or 26' in the patterned portion 28 to achieve both fusing and a desired level of antioxidant. In one example, the weight ratio of the antioxidant blend in the selectively applied antioxidant formulation 34 to the energy absorber in the selectively applied fusing agent 26, 26' is about 0.1 to about 5. In another example, the weight of the antioxidant blend applied to the portion 28 is about 1.5 to about 2.25 times the weight of the energy absorber applied to the portion 28. Depending on the 3D printer, the print pattern can also be adjusted to offset any cooling effect.

[0187] The antioxidant formulation 34 can also be applied to the unpatterned portion 40 (which does not have the fusing agent 26 or 26' applied to it). Accordingly, some examples of the method 100 further include selectively applying the antioxidant formulation 34 to another portion 40 of the build material layer 10 on which no fusing agent 26 or 26' is present. Applying the antioxidant formulation 34 in this portion 40 helps to reduce thermal degradation of the polymeric build material composition 12. This can improve the recyclability / reusability of the polymeric build material composition 12.

[0188] As noted, one or more portions 40 are not patterned with the fusing agent 26, 26', and thus will not be part of the final 3D object layer 30. However, thermal energy generated during the radiation exposure process can propagate into the surrounding one or more portions 40 that do not have the fusing agent 26, 26' applied to them. When the antioxidant formulation 34 is applied in the one or more unpatterned portions 40, it can help to inhibit the propagation of thermal energy into the one or more unpatterned portions 40. Alternatively, when the antioxidant formulation 34 is applied in the patterned portion 28 but not in the one or more unpatterned portions 40, the detailing agent 38 can be selectively applied to the one or more portions 40 of the layer 10. The detailing agent 38 also inhibits the propagation of thermal energy, and thereby helps to prevent coalescence of the one or more unpatterned portions of build material 40.

[0189] After the selective application of the agent / formulation 26 or 26', 34 and in some cases 38 in one or more particular portions 28 or 28, 40 of the layer 10, the entire layer 10 of the build material composition 12 is exposed to electromagnetic radiation (shown as EMR in Figure 2 .

[0190] The electromagnetic radiation is emitted by the radiation source 24. The length of time that the electromagnetic radiation is applied or the energy exposure time can depend on one or more of, for example: the characteristics of the radiation source 24; the characteristics of the build material composition 12; and / or the characteristics of the fusing agent 26, 26'.

[0191] It is to be understood that the exposure to electromagnetic radiation can be accomplished in a single radiation event or in multiple radiation events. In one example, the exposure of the build material composition 12 is accomplished in multiple radiation events. In a specific example, the number of radiation events is from 3 to 8. In another specific example, the exposure of the build material composition 12 to electromagnetic radiation can be accomplished in 3 radiation events. It can be desirable to expose the build material composition 12 to electromagnetic radiation in multiple radiation events to counteract a cooling effect that can be caused by an amount of the agent 26 or 26', 34 and in some cases 38 applied to the build material layer 10. Further, it can be desirable to expose the polymeric build material composition 12 to electromagnetic radiation in multiple radiation events to sufficiently increase the temperature of the polymeric build material composition 12 in the one or more patterned portions 28 without excessively heating the build material composition 12 in the one or more unpatterned portions 40.

[0192] The fusing agent 26 or 26' enhances the absorption of the radiation, converts the absorbed radiation into heat energy, and facilitates the transfer of heat to the polymeric build material composition 12 in contact therewith. In one example, the fusing agent 26, 26' sufficiently increases the temperature of the polymeric build material composition 12 in the portion 28 to a temperature above the melting point of the polymeric material or within the melting range of the polymeric material to allow coalescence / fusing (e.g., thermal welding, melting, bonding, etc.) of the polymeric build material composition 12 to occur. The application of electromagnetic radiation forms a 3D object layer 30 that can have improved quality (e.g., as compared to a 3D object layer formed without the antioxidant formulation).

[0193] In some examples, the electromagnetic radiation has a wavelength of from 800 nm to 4000 nm, or from 800 nm to 1400 nm, or from 800 nm to 1200 nm. Radiation having a wavelength within the ranges provided can be absorbed (e.g., 80% or more of the applied radiation) by the fusing agent 26, 26' and can heat the polymeric build material composition 12 in contact therewith, and can be substantially not absorbed (e.g., 25% or less of the applied radiation) by the unpatterned polymeric build material composition 12 in the one or more portions 40.

[0194] After the formation of the 3D object layer 30, one or more additional layers can be formed thereon to create an instance of the 3D object. To form the next layer, additional polymer build material composition 12 can be applied over the layer 30. Subsequently, fusing agent 26 or 26' is selectively applied over at least a portion of the additional build material composition 12 according to the 3D object model. Oxidation inhibitor formulation 34 can also be selectively applied over the patterned portion 28 and, in some cases, over the unpatterned portion 40. Refining agent 38 can be applied in any areas of the additional build material composition 12 where coalescence is not desired. After the application of one or more agents / formulations 26 or 26', 34 and, in some cases, 38, the entire layer of additional polymer build material composition 12 is exposed to electromagnetic radiation in the manner described herein. The application of additional polymer build material composition 12, the selective application of one or more agents 26 or 26', 34 and, in some cases, 38, and the electromagnetic radiation exposure can be repeated a predetermined number of cycles according to the 3D object model to form the final 3D object 30.

[0195] Printing with antioxidant formulation and two fusing agents

[0196] Referring now to Figure 3 , an example of a method 200 employing both an oxidation inhibitor formulation 34 and a fusing agent 26 and 26' is depicted.

[0197] Figure 3 The method 200 shown includes applying a polymer build material composition to form a build material layer (reference numeral 202); selectively applying a core fusing agent and an oxidation inhibitor formulation to the build material layer based on a 3D object model, thereby forming a first patterned portion (reference numeral 204); selectively applying a primer fusing agent and an oxidation inhibitor formulation to the build material layer based on the 3D object model, thereby forming a second patterned portion adjacent to the first patterned portion (reference numeral 206); and exposing the build material layer 10 to energy to selectively coalesce the patterned portions and form a 3D object layer (reference numeral 208).

[0198] The method 200 is shown schematically in Figure 4 . In Figure 4 , a layer 10 of polymer build material composition 12 is applied on the build area platform 14 as described with reference to Figure 2 . After the polymer build material composition 12 has been applied and prior to further processing, the build material layer 10 can be exposed to a pre-heat as described with reference to Figure 2 .

[0199] In this example of the method 200, one or more core fusing agents 26 and antioxidant formulations 34 are selectively applied over at least some of the polymeric build material composition 12 in the layer 10 to form a first patterned portion 28; and one or more priming fusing agents 26' and antioxidant formulations 34 are selectively applied over at least some of the polymeric build material composition 12 in the layer 10 to form one or more second patterned portions 32 adjacent to the first patterned portion 28. The first patterned portion 28 is generally located in the interior of the build material layer 10, and the second patterned portion 32 is generally located in the exterior of the build material layer 10, where it is desirable to provide a white appearance or other color at one or more surfaces of the 3D printed object layer 30'.

[0200] The volume of core fusing agent 26 applied per unit of polymeric build material composition 12 in the first patterned portion 28 can be sufficient to absorb and convert enough electromagnetic radiation to cause the build material composition 12 in the patterned portion 28 to coalesce / fuse.

[0201] The volume of priming fusing agent 26' applied per unit of polymeric build material composition 12 in the second patterned portion 32 can be sufficient to absorb and convert enough electromagnetic radiation to cause the build material composition 12 in the second patterned portion 32 to coalesce / fuse.

[0202] The volume of antioxidant formulation 34 applied per unit of polymeric build material composition 12 in the first and second patterned portions 28, 32 can depend on the voxel volume and the volume of fusing agent 26, 26' applied. The weight ratio of antioxidant blend to corresponding energy absorber can be controlled to achieve both coalescence and antioxidant properties.

[0203] In this example, the layer 10 is exposed to electromagnetic radiation (shown in Figure 4 In the example shown, a detailing agent 38 is also selectively applied to one or more portions 40 of the layer 10. The one or more portions 40 are not patterned with fusing agent 26, 26', and thus will not be part of the final 3D object layer 30'. In other examples, the antioxidant formulation 34 can be applied to the one or more portions 40 instead of the detailing agent 38. In some examples, the detailing agent 38 can also be applied to the one or more portions 28 that are patterned with fusing agent 26, 26' and antioxidant formulation 34. In these examples, the detailing agent 38 can be used to adjust the level of fusing in a particular region, to prevent overheating of the one or more patterned portions 28, etc.

[0204] After the selective application of agents 26, 26', 34 and in some cases 38 in the one or more particular portions 28, 32 and 40 of the layer 10, the entire layer 10 of build material composition 12 is exposed to electromagnetic radiation (shown in Figure 4 as EMR). The radiation exposure can be referenced to the build material composition 12 in the one or more portions 28, 32 and 40 that are patterned with fusing agent 26, 26' and antioxidant formulation 34.Figure 2 The above is to be completed.

[0205] In this example, the corresponding fluxes 26 and 26' enhance radiation absorption, convert the absorbed radiation into heat energy, and promote heat transfer to the building material composition 12 in contact with it. In one example, fluxes 26 and 26' sufficiently raise the temperature of the polymer building material composition 12 in the corresponding portions 28 and 32 to above the melting point of the polymer material or within the melting range of the polymer material to allow coalescence / fusion (e.g., thermal bonding, melting, adhesion, etc.) of the polymer building material composition 12 to occur. The application of electromagnetic radiation forms a 3D object layer 30', which in this example includes a core portion 44 and an outer portion 36 at opposite ends of the core portion 44. The entire 3D object layer 30' may have improved component quality due to the antioxidant formulation 34.

[0206] Figure 4 An example is shown of how the core fusion agent 26, the base fusion agent 26', and the antioxidant formulation 34 can be used together to pattern a single building material layer 10.

[0207] When the two fusion agents 26 and 26' are used to construct a 3D object, it is desirable to use core fusion agent 26 to form to the core (e.g., center or innermost part) of the 3D object, and it is desirable to use underlay fusion agent 26' to form the outermost layer of the 3D object. Core fusion agent 26 can provide strength to the core of the 3D object, while underlay fusion agent 26' can exhibit white or colored appearance on the exterior of the 3D object. It is to be understood that antioxidant formulation 34 can also be used to prevent thermal degradation of polymer build material composition 12 throughout the 3D printing process.

[0208] An example of a 3D object 46 formed using base filler 26', core filler 26, and antioxidant formulation 34 is shown. Figure 5 In this instance of forming the 3D object 46, a core flux 26 and an antioxidant formulation 34 are applied to multiple layers of the build material composition 12 to pattern and ultimately form the inner portions 48 and 50 of the 3D printed object 46, and a base flux 26' and an antioxidant formulation 34 are applied to multiple layers of the build material composition 12 to pattern and ultimately form the outermost portions 52 and 54 of the 3D printed object 46. After each build material layer 10 is patterned with one or more reagents 26, 34 or 26', 34, electromagnetic radiation may be applied to cure the corresponding patterned build material layer.

[0209] Another example of method 300 using each of reagents 26, 26', and 34 is shown in Figure 6 In the middle, and the resulting 3D object 56 instances are displayed Figure 7 middle.

[0210] The method 300 includes, based on the 3D object model, selectively applying a core fusing agent and an antioxidant formulation on a first layer of the polymeric build material composition to form a patterned portion (reference 302); exposing the first layer to energy to selectively coalesce the patterned portion and form a core layer (reference 304); applying a second layer of the polymeric build material composition on the core layer (reference 306); based on the 3D object model, selectively applying a priming fusing agent and an antioxidant formulation on at least a portion of the second layer to form a second patterned portion (reference 308); and exposing the second layer to energy to selectively coalesce the second patterned portion and form a 3D object layer (in this example, a priming layer) (reference 310). Some examples of the method 300 further include selectively applying the priming fusing agent 26’ and the antioxidant formulation 34 on the first layer at a region adjacent to the patterned portion 28, whereby the region coalesces to form an edge portion adjacent to the core layer.

[0211] Figure 7 One example of a 3D object 56 formed using the method 300 is shown in FIG. 5B. To form this example of the 3D object 56, one or more outermost build material layers and outermost edges of intermediate build material layers are patterned with the priming fusing agent 26’ and the antioxidant formulation 34 to form 3D object layers 58, 60. In this example, the outermost build material layers are patterned with the priming fusing agent 26’ and the antioxidant formulation 34 to form the 3D object layers 58, 60. Figure 7 In the example shown, the innermost portion of the intermediate build material layers will be patterned with the core fusing agent 26 and the antioxidant formulation 34 to form a core portion 62 of the object 56.

[0212] In this example of the method 300, any number of core layers 62 can be formed, and any number of 3D object layers 58, 60 can be formed.

[0213] In one example of the method 300, the predetermined number of 3D object layers (i.e., the core layers 62) are formed by repeatedly applying the polymeric build material composition 12 to form respective build material layers 10; selectively applying the core fusing agent 26 and the antioxidant formulation 34 over the respective build material layers 10 to form respective patterned portions 28; and exposing the respective build material layers to energy. In some examples, the predetermined number of 3D object layers (i.e., the core layers 62) are formed on top of the predetermined number of 3D object layers (i.e., the primer layers 58, 60). In these examples, the method 300 can further include forming a second predetermined number of 3D object layers (i.e., the primer layers 58, 60) on the predetermined number of 3D object layers (i.e., the core layers 62) by repeatedly applying the polymeric build material composition 12 to form additional individual build material layers 10; selectively applying the primer fusing agent 26' and the antioxidant formulation 34 over the additional individual build material layers 10 to form additional individual patterned portions 32; and exposing the additional individual build material layers to energy.

[0214] In Figure 7 In the example shown, a colorizing agent can also be applied with the primer fusing agent 26' and the antioxidant formulation 34 to produce a color at the outer surface of the object 56. For example, a colorizing agent can be applied with the primer fusing agent 26' and the antioxidant formulation 34 on the build material forming the 3D object layers 58. Since the primer fusing agent 26' and the antioxidant formulation 34 are transparent or slightly colored, and the polymeric build material composition 12 is white or off-white, the color of the colorizing agent will be the color of the resulting 3D object layers 58. The colorizing agent of the colorizing agent becomes embedded in the coalesced / fused build material composition throughout the 3D object layers 58. In this example, the 3D object layers 60, which are white or off-white, can or can not have a colorizing agent applied thereto. These intermediate layers 60 can help to shield the black (or dark) core layers 62 as they optically isolate the core layers 62.

[0215] While several variations of the combination of the objects 46, 56 and the fusing agents 26, 26' have been described, it is understood that the fusing agents 26, 26' and the antioxidant formulation 34 can be used to form any desired 3D object.

[0216] In any example of the methods 100, 200, 300 disclosed herein, any agent (fusing agent 26, 26', antioxidant formulation 34, detailing agent 38, and / or colorizing agent) can be dispensed by the applicator 42, 42', 42" (shown in Figure 2 and Figure 4The one or more applicators 42, 42', 42" can each be thermal inkjet printheads, piezoelectric printheads, continuous inkjet printheads, and the like, and can enable selective application of the fusing agent 26, 26', antioxidant formulation 34, detailing agent 38, and / or coloring agent via thermal inkjet printing, piezoelectric inkjet printing, continuous inkjet printing, and the like. A controller can process data and, in response, control the one or more applicators 42, 42', 42" to deposit the fusing agent 26, 26', antioxidant formulation 34, detailing agent 38, and / or coloring agent onto one or more predetermined portions of the polymeric build material composition 12. It is to be understood that the applicators 42, 42', 42" can be separate applicators or a single applicator with several separate cartridges for dispensing the respective agents.

[0217] It is to be understood that the selective application of any of the fusing agent 26, 26', antioxidant formulation 34, detailing agent 38, and / or coloring agent can be accomplished in a single print pass or in multiple print passes. In some examples, one or more agents / formulations are selectively applied in a single print pass. In other examples, one or more agents are selectively applied in multiple print passes. In one of these examples, the number of print passes is 2 to 4. In still other examples, 2 or 4 print passes are used. It can be desirable to apply the fusing agent 26, 26', antioxidant formulation 34, detailing agent 38, and / or coloring agent in multiple print passes to increase the amount of energy absorber, antioxidant blend, colorant, and the like applied to the polymeric build material composition 12, to avoid liquid splatter, to avoid displacement of the build material composition 12, and the like.

[0218] To further illustrate the present disclosure, examples are set forth herein. It is to be understood that these examples are provided for illustrative purposes and should not be construed as limiting the scope of the present disclosure.

[0219] Example

[0220] Examples of the antioxidant formulations described herein were prepared and tested to evaluate their effectiveness on polyamide build materials.

[0221] Prior to forming the antioxidant formulations, several antioxidant dispersions were first prepared. Two exemplary antioxidant dispersions were prepared with the same primary antioxidant (i.e., Irganox® 1010) and secondary antioxidant (i.e., Irgafos® 168). The first antioxidant dispersion (referred to as "first AO dispersion") included a dispersant (i.e., Irgafos® 38) and the second antioxidant dispersion (referred to as "second AO dispersion") included a dispersant (i.e., Irgafos® 245). 245) and secondary antioxidant (i.e., Irgafos® 168). The first antioxidant dispersion (referred to as "first AO dispersion") included a dispersant (i.e., Irgafos® 38) and the second antioxidant dispersion (referred to as "second AO dispersion") included a dispersant (i.e., Irgafos® 245). 683) and the second antioxidant dispersion (referred to as "second AO dispersion") included a dispersant (i.e., Irgafos® 245). 683) and a surfactant combination (i.e., a mixture of stearyl alcohol and sodium stearate). A control antioxidant dispersion (referred to herein as "control AO dispersion") was also prepared with the same primary antioxidant and secondary antioxidant, but without the dispersant or surfactant. The formulation of each dispersion is shown in Table 1. The following abbreviations are used in Table 1 : DLTDP is dilauryl thiodipropionate, KOH is potassium hydroxide, and DI H2O is deionized water.

[0222] Table 1 - AO dispersions

[0223] .

[0224] To generate the control AO dispersion, the primary antioxidant and secondary antioxidant were first melted at a temperature of about 100 °C to about 120 °C with constant stirring. Once melted, the temperature was reduced to about 75 °C and stirring was continued. While stirring, the KOH solution was added and the DI H2O was added dropwise. This formed a highly viscous but still stirrable paste. Additional H2O was added and the mixture was allowed to cool to room temperature.

[0225] To generate the first AO dispersion, the primary antioxidant and secondary antioxidant were first melted at a temperature of about 100 °C to about 120 °C with the dispersant. Once melted, the temperature was reduced to about 75 °C and stirring was continued. While stirring, the KOH solution was added and the DI H2O was added dropwise. This formed a highly viscous but still stirrable paste. Additional H2O was added and the mixture was allowed to cool to room temperature.

[0226] To generate the second AO dispersion, the primary antioxidant and secondary antioxidant were first melted at a temperature of about 100 °C to about 120 °C with the dispersant and surfactant. Once melted, the temperature was reduced to about 75 °C and stirring was continued. While stirring, the KOH solution was added and the DI H2O was added dropwise. This formed a highly viscous but still stirrable paste. Additional H2O was added and the mixture was allowed to cool to room temperature.

[0227] Each antioxidant dispersion was subsequently placed in a ball mill for 48 hours to reduce the particle size.

[0228] After ball milling, particle size measurements were taken on each antioxidant dispersion using a Microtrac particle size analyzer. Visual analysis was also performed on each antioxidant dispersion.

[0229] The particle size measurements of the first and second AO dispersions were compared to the particle size measurements of the control dispersion, indicating that a more uniform particle size distribution with a higher concentration of sub-micron particles can be achieved when using a dispersant or a dispersant with a surfactant. The visual results clearly indicated that the first AO dispersion and the second AO dispersion were uniformly dispersed. In contrast, the control AO dispersion was not dispersed and the solids were clearly settled at the bottom of the container.

[0230] The first AO dispersion was subsequently used to generate an exemplary antioxidant formulation. The exemplary antioxidant formulation included the first AO dispersion and a liquid carrier (co-solvent, surfactant, DI H2O). The formulation of the exemplary antioxidant formulation is shown in Table 2.

[0231] Table 2 - Exemplary AO Formulation

[0232] .

[0233] The exemplary AO formulation was subsequently printed with a thermal inkjet printhead to determine printability and decap performance. A magenta dye was included in the exemplary AO formulation to enhance the visibility of the printed article. The print results showed very good decap performance and nozzle health. As such, the exemplary AO formulation exhibited acceptable print performance.

[0234] The exemplary AO formulation was subsequently tested to determine its effect on yellowing and discoloration on a polyamide build material. The materials, amounts, and conditions used in the test simulated a 3D printing process.

[0235] For this test, the exemplary AO formulation was incorporated into a virgin polyamide-12 (PA-12) powder. More specifically, the PA-12 was dry blended with 10% (by weight) of the exemplary AO formulation. This combination was referred to as “Example 1”.

[0236] Two different comparative examples were also prepared. One comparative example was a virgin polyamide-12 build material without any AO formulation added. This comparative example was referred to as “Comparative Example 2”. Another comparative example included a virgin polyamide-12 build material with 10% (by weight) of a comparative AO formulation. The comparative AO formulation included the liquid carrier described in Table 2 above, without the first AO dispersion. This comparative example was referred to as “Comparative Example 3”.

[0237] Subsequently, an aging process was applied to all of the build material samples (Example 1, Comparative Example 2, Comparative Example 3) by placing the materials in an oven at 165°C for 20 hours. The samples were then removed from the oven and homogenized.

[0238] L* and b* measurements were made on fresh (unaged) polyamide-12 samples (fresh control) as well as on aged Example 1, Control Example 2, and Comparative Example 3. The L* and b* measurements were made using a X-Rite® eXact spectrophotometer. TM The L* and b* measurements were made using a spectrophotometer. L* is a measure of lightness / whiteness, from black (L* = 0) to white (L* = 100). Similarly, b* is a measure of blue to yellow, and is blue (negative values) to yellow (positive values). The L* results are shown in Table 3, and the results for b* are shown in Figure 8 Table 4. Table 3 depicts the three measurements, the average of the three measurements, and the standard deviation (stdev). Figure 8 The average of the three measurements is depicted.

[0239] Table 3 - L* Results

[0240]

[0241] Aged Example 1 showed significant improvement in both L* and b* values after oven aging, when compared to aged Control Example 2 and aged Comparative Example 3. Aged Example 1 had less than a 10% change in b* (determined by comparison to the fresh control), and exhibited the least amount of yellowing when subjected to thermal stress, which is common in 3D printing applications.

[0242] Raw color photographs were taken of each of the fresh (unaged) polyamide-12 samples ("fresh control"), aged Control Example 2, aged Comparative Example 3, and aged Example 1, and are shown in black and white in Figure 9A , 9B , 9C, and 9D, respectively. The visual results correlate with the L* and b* measurements. In particular, aged Example 1 yellowed less than aged Control Example 2 or aged Comparative Example 3.

[0243] It is to be understood that the ranges provided herein include the specified ranges and any values or sub-ranges within the specified ranges. For example, about 0.01 wt% to about 5 wt% should be interpreted to include not only the explicitly recited limits of about 0.01 wt% to about 5 wt%, but also individual values, such as about 0.25 wt%, about 0.55 wt%, about 1.74 wt%, about 2.03 wt%, about 3.2 wt%, about 4.5 wt%, etc., and sub-ranges, such as about 0.2 wt% to about 4.8 wt%, about 1 wt% to about 4 wt%, about 0.5 wt% to about 3.5 wt%, etc. Furthermore, when a numerical value is described as "about," this is intended to encompass minor variations (up to + / - 10%) from the specified value.

[0244] References throughout this specification to "one example," "another example," "an example," and so on, mean that a particular element (e.g., feature, structure, and / or characteristic) described in connection with the example is included in at least one example described herein, and can or can not be present in other examples. In addition, it should be understood that references to any example are intended to refer to the particular structure, feature, characteristic, or combination of structures, features, and / or characteristics being described in connection with that example, and that no single example is necessarily limited by the occurrence of the reference. Furthermore, it should be understood that any reference to prior art does not constitute an admission as prior art of any description or disclosure used in connection with the prior art.

[0245] In describing and claiming the examples disclosed herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0246] While several examples have been described and illustrated, it is understood that these examples can be modified. Therefore, the preceding description should be considered as merely illustrative of the described examples.

Claims

1. Methods of 3D printing, including: Apply a polymeric building material composition to form a building material layer; Based on a 3D object model, a bonding agent is selectively applied to at least a portion of the building material layer; Based on a 3D object model, an antioxidant formulation is selectively applied to at least said portions of the material layer, wherein the antioxidant formulation comprises: water; Water-soluble or water-miscible organic cosolvents; Surfactants, dispersants, or combinations thereof; and An antioxidant blend consisting of a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant is a hydrogen atom or electron donor and the secondary antioxidant is a peroxide scavenger; and The building material layer is exposed to electromagnetic radiation to coalesce at least a portion to form a layer of a 3D object.

2. The method as defined in claim 1, further comprising selectively applying an antioxidant formulation to other portions of the building material layer thereon that do not have a binder.

3. A jettable antioxidant formulation for use in the method of 3D printing according to claim 1, comprising: An antioxidant blend consisting of a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant is a hydrogen atom or electron donor and the secondary antioxidant is a peroxide scavenger; Surfactants, dispersants, or combinations thereof; Water-soluble or water-miscible organic cosolvents; and water.

4. The sprayable antioxidant formulation as defined in claim 3, wherein the antioxidant blend is present in an amount of 1% to 15% by weight of active ingredient of the total weight of the sprayable antioxidant formulation.

5. The sprayable antioxidant formulation as defined in claim 3, wherein the primary antioxidant and the secondary antioxidant are present in a weight ratio of 1:1 to 1:

5.

6. The sprayable antioxidant formulation as defined in claim 3, wherein: The formulation contains both a surfactant and a dispersant; The surfactant is a mixture of stearyl alcohol and sodium stearate; and The dispersant is selected from styrene-acrylic copolymers, polyvinyl alcohol, vinyl alcohol copolymers, and combinations thereof.

7. The sprayable antioxidant formulation as defined in claim 3, wherein the primary antioxidant and the secondary antioxidant each have an average particle size of 10 nm to 800 nm.

8. The sprayable antioxidant formulation as defined in claim 3, wherein: The main antioxidant is hindered phenol; and Secondary antioxidants are selected from thioethers, thioesters, phosphites, and combinations thereof.

9. A multifluidic kit for use in the method of 3D printing according to claim 1, comprising: A binder containing water and an electromagnetic radiation absorber; and The antioxidant formulation according to claim 3.

10. The multifluid kit as defined in claim 9, wherein: The main antioxidant is hindered phenol; and Secondary antioxidants are selected from thioethers, thioesters, phosphites, and combinations thereof.

11. The multifluid kit as defined in claim 9, wherein the antioxidant blend is present in an amount of 1% to 15% by weight of active ingredient of the total antioxidant formulation.

12. The multifluid kit as defined in claim 9, wherein the primary antioxidant and the secondary antioxidant are present in a weight ratio of 1:1 to 1:

5.

13. The multifluid kit as defined in claim 9, further comprising: Coloring agents selected from black, cyan, magenta, or yellow inks; or A refining agent containing surfactants, cosolvents, and water; or Both coloring agents and refining agents.

14. The multifluid kit as defined in claim 9, wherein the flux is a core flux and the electromagnetic radiation absorber has absorption at a wavelength of at least 400 nm to 780 nm.

15. The multifluid kit as defined in claim 9, wherein the flux is a base flux and the electromagnetic radiation absorber is a plasma resonance absorber having absorption at wavelengths from 800 nm to 4000 nm and transparency at wavelengths from 400 nm to 780 nm.

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