FIELD OF THE INVENTION

The invention relates to a method for manufacturing a 3D (printed) item. The invention also relates to the 3D (printed) item obtainable with such method. Further, the invention relates to a lighting device including such 3D (printed) item.

BACKGROUND OF THE INVENTION

The use of a thermoplastic polymer comprising a particulate filler for preparing 3D articles is known in the art. WO2017/040893, for instance, describes a powder composition, wherein the powder composition comprises a plurality of thermoplastic particles characterized by a bimodal particle size distribution, and wherein the powder composition may further comprise a particulate filler, antioxidant, heat stabilizer, light stabilizer, ultraviolet light stabilizer, ultraviolet light absorbing additive, near infrared light absorbing additive, infrared light absorbing additive, plasticizer, lubricant, release agent, antistatic agent, anti-fog agent, antimicrobial agent, colorant, laser marking additive, surface effect additive, radiation stabilizer, flame retardant, anti-drip agent, fragrance, fiber, or a combination comprising at least one of the foregoing, preferably a colorant or a metal particulate. This document further describes a method of preparing a three-dimensional article, the method comprising powder bed fusing the powder composition to form a three- dimensional article.

SUMMARY OF THE INVENTION

Within the next 10-20 years, digital fabrication will increasingly transform the nature of global manufacturing. One of the aspects of digital fabrication is 3D printing. Currently, many different techniques have been developed in order to produce various 3D printed objects using various materials such as ceramics, metals, and polymers. 3D printing can also be used in producing molds which can then be used for replicating objects.

For the purpose of making molds, the use of polyjet technique has been suggested. This technique makes use of layer by layer deposition of photo-polymerizable material which is cured after each deposition to form a solid structure. While this technique produces smooth surfaces the photo curable materials are not very stable, and they also have relatively low thermal conductivity to be useful for injection molding applications.

The most widely used additive manufacturing technology is the process known as Fused Deposition Modeling (FDM). Fused deposition modeling (FDM) is an additive manufacturing technology commonly used for modeling, prototyping, and production applications. FDM works on an “additive” principle by laying down material in layers; a plastic filament or metal wire is unwound from a coil and supplies material to produce a part. Possibly, (for thermoplastics for example) the filament is melted and extruded before being laid down. FDM is a rapid prototyping technology. Other terms for FDM are “fused filament fabrication” (FFF) or “filament 3D printing” (FDP), which are considered to be equivalent to FDM. In general, FDM printers use a thermoplastic filament, which is heated to its melting point and then extruded, layer by layer, (or in fact filament after filament) to create a three-dimensional object. FDM printers are relatively fast, low cost and can be used for printing complicated 3D objects. Such printers are used in printing various shapes using various polymers. The technique is also being further developed in the production of LED luminaires and lighting solutions.

It appears desirable to produce items, such as luminaires, with controlled optical and/or mechanical properties. This may be desirable for controlling light distributions, to create light effects, for distinguishing surfaces, for (traffic) signs or safety reflection elements.

It is an object of the invention to provide an alternative 3D printing method and/or 3D (printed) item which preferably further at least partly obviate(s) one or more of above-described drawbacks.

In a first aspect, the invention provides a method for producing a 3D item by means of fused deposition modelling (FDM).

The 3D item has a stack of layer levels in a stacking direction. The layer levels have additive comprising layer levels, each additive comprising layer level having one or more additive comprising layers. Each additive comprising layer has an additive comprising zone with an additive at an additive concentration. The additive (for example, particles) is one or more of (i) reflective for light, (ii) light absorbing, (iii) transmissive for light, and (iv) luminescent. Each additive comprising layer level has an accumulated additive comprising zone width, being the accumulated width of the additive comprising zones of the additive comprising layers in a direction perpendicular to the stacking direction. The method comprises a 3D printing stage during which a 3D printable material is deposited to provide the 3D item. As is common for fused deposition modelling, the 3D printable material is comprised in an extrudate, and the extrudate is deposited in a layer-wise manner on a receiver item to provide the 3D item comprising 3D printed material. During the 3D printing stage, the additive concentration is increased or decreased depending on the accumulated additive comprising zone width.

The method according to the first aspect of the invention is hereinbelow further explained with particles as examples of additives. However, other examples of additives may also be possible.

With the above method, it may be possible to create amongst others one or more of (i) a decorative effect, and (ii) an optical effect that may be either constant or enhanced over the 3D printed item (surface). Further, it may be possible to control mechanical aspects and optical aspects at the same time. In principle, with a single type of printing material (for example a combination of (a) printable material and (b) particles) it may be possible to create one or more 3D printed parts that have varying widths, wherein optical properties may be constant or enhanced, whereas the material composition may substantially, or even essentially, be the same (over all these parts). This may allow a relatively simple 3D printing method but may also add to the controllability of local material properties of the 3D printed item.

Hereinbelow, first some general aspects are described and then some implementations of the invention are described.

As indicated above, the method comprises depositing during a printing stage 3D printable material. Herein, the term “3D printable material” refers to the material to be deposited or printed, and the term “3D printed material” refers to the material that is obtained after deposition. These materials may be essentially the same, as the 3D printable material may especially refer to the material in a printer head or extruder at elevated temperature and the 3D printed material refers to the same material, but in a later stage when deposited. The 3D printable material is printed as a filament and deposited as such. The 3D printable material may be provided as filament or may be formed into a filament. Hence, whatever starting materials are applied, a filament comprising 3D printable material is provided by the printer head and 3D printed. The term “extrudate” may be used to define the 3D printable material downstream of the printer head, but not yet deposited. The latter is indicated as “3D printed material”. In fact, the extrudate comprises 3D printable material, as the material is not yet deposited. Upon deposition of the 3D printable material or extrudate, the material is thus indicated as 3D printed material. Essentially, the materials are the same material, as the thermoplastic material upstream of the printer head, downstream of the printer head, and when deposited, is essentially the same material.

Herein, the term “3D printable material” may also be indicated as “printable material. The term “polymeric material” may refer to a blend of different polymers but may also refer to essentially a single polymer type with different polymer chain lengths. Hence, the terms “polymeric material” or “polymer” may refer to a single type of polymers but may also refer to a plurality of different polymers. The term “printable material” may refer to a single type of printable material but may also refer to a plurality of different printable materials. The term “printed material” may refer to a single type of printed material but may also refer to a plurality of different printed materials.

Hence, the term “3D printable material” may also refer to a combination of two or more materials. In general, these (polymeric) materials have a glass transition temperature Tg and/or a melting temperature Tm. The 3D printable material will be heated by the 3D printer before it leaves the nozzle to a temperature of at least the glass transition temperature, and in general at least the melting temperature. Hence, the 3D printable material may comprise a thermoplastic polymer having a glass transition temperature (T _g ) and /or a melting point (T _m ), and the printer head action comprises heating the 3D printable material above the glass transition and if it is a semi-crystalline polymer above the melting temperature. The 3D printable material may also comprise a (thermoplastic) polymer having a melting point (T _m ), and the printer head action comprises heating the 3D printable material to be deposited on the receiver item to a temperature of at least the melting point. The glass transition temperature is in general not the same thing as the melting temperature. Melting is a transition which occurs in crystalline polymers. Melting happens when the polymer chains fall out of their crystal structures and become a disordered liquid. The glass transition is a transition which happens to amorphous polymers; that is, polymers whose chains are not arranged in ordered crystals, but are just strewn around in any fashion, even though they are in the solid state. Polymers can be amorphous, essentially having a glass transition temperature and not a melting temperature or can be (semi) crystalline, in general having both a glass transition temperature and a melting temperature, with in general the latter being larger than the former. The glass temperature may be determined with differential scanning calorimetry. The melting point or melting temperature can also be determined with differential scanning calorimetry. As indicated above, the invention thus provides a method comprising providing a filament of 3D printable material and printing during a printing stage said 3D printable material on a substrate, to provide said 3D item.

Materials that may qualify as 3D printable materials can be selected from the group consisting of metals, glasses, thermoplastic polymers, and silicones. The 3D printable material may comprise a (thermoplastic) polymer selected from the group consisting of acrylonitrile butadiene styrene (ABS), polyamide (such as Nylon), acetate (or cellulose), polylactic acid (PLA), terephthalate (such as polyethylene terephthalate (PET)), acrylic (polymethylacrylate, Perspex, polymethylmethacrylate (PMMA)), polypropylene (or polypropene), polycarbonate (PC), polystyrene (PS), PE (such as expanded high impact- polythene (or polyethene), low density (LDPE) high density (HDPE)), polyvinylchloride (PVC), poly chloroethene, such as thermoplastic elastomer based on copolyester elastomers, polyurethane elastomers, polyamide elastomers polyolefine-based elastomers, or styrene- based elastomers. Optionally, the 3D printable material comprises a 3D printable material selected from the group consisting of urea formaldehyde, polyester resin, epoxy resin, melamine formaldehyde, and thermoplastic elastomer. Optionally, the 3D printable material comprises a 3D printable material selected from the group consisting of a poly sulfone. Elastomers, especially thermoplastic elastomers, are especially interesting as they are flexible and may help obtaining relatively more flexible filaments comprising the thermally conductive material. A thermoplastic elastomer may comprise one or more of styrenic block copolymers (TPS (TPE-s)), thermoplastic polyolefin elastomers (TPO (TPE-o)), thermoplastic vulcanizates (TPV (TPE-v or TPV)), thermoplastic polyurethanes (TPU (TPU)), thermoplastic copolyesters (TPC (TPE-E)), and thermoplastic polyamides (TPA (TPE-A)).

Suitable thermoplastic materials, such as also mentioned in WO2017/040893, may include one or more of polyacetals (such as polyoxyethylene and polyoxymethylene), poly(Cl-6 alkyl)acrylates, polyacrylamides, polyamides, (such as aliphatic polyamides, polyphthalamides, and polyaramides), polyamideimides, polyanhydrides, polyarylates, polyarylene ethers (such as polyphenylene ethers), polyarylene sulfides (such as polyphenylene sulfides), polyarylsulfones (such as polyphenylene sulfones), polybenzothiazoles, polybenzoxazoles, polycarbonates (including polycarbonate copolymers such as polycarbonate-siloxanes, polycarbonate-esters, and polycarbonate-ester-siloxanes), polyesters (such as polycarbonates, polyethylene terephthalates, polyethylene naphtholates, polybutylene terephthalates, polyarylates), and polyester copolymers such as polyester- ethers), polyetheretherketones, polyetherimides (including copolymers such as polyetherimide-siloxane copolymers), polyetherketoneketones, polyetherketones, poly ethersulfones, polyimides (including copolymers such as polyimide- siloxane copolymers), poly(Cl-6 alkyl)methacrylates, polymethacrylamides, polynorbomenes (including copolymers containing norbomenyl units), polyolefins (such as polyethylenes, polypropylenes, polytetrafluoroethylenes, and their copolymers, for example ethylene- alpha- olefin copolymers), polyoxadiazoles, polyoxymethylenes, polyphthalides, polysilazanes, polysiloxanes, polystyrenes (including copolymers such as acrylonitrile-butadiene-styrene (ABS) and methyl methacrylate-butadiene-styrene (MBS)), polysulfides, polysulfonamides, polysulfonates, polysulfones, polythioesters, polytriazines, polyureas, polyurethanes, polyvinyl alcohols, polyvinyl esters, polyvinyl ethers, polyvinyl halides, polyvinyl ketones, polyvinyl thioethers, polyvinylidene fluorides, or the like, or a combination comprising at least one of the foregoing thermoplastic polymers. Examples of polyamides are synthetic linear polyamides, for example Nylon-6, 6; Nylon-6, 9; Nylon-6, 10; Nylon-6, 12; Nylon-11; Nylon-12 and Nylon-4, 6, preferably Nylon 6 and Nylon 6,6, or a combination comprising at least one of the foregoing. Polyurethanes that can be used include aliphatic, cycloaliphatic, aromatic, and polycyclic polyurethanes, including those described above. Also useful are poly(Cl-6 alkyl)acrylates and poly(Cl-6 alkyl)methacrylates, which include, for instance, polymers of methyl acrylate, ethyl acrylate, acrylamide, methacrylic acid, methyl methacrylate, n-butyl acrylate, and ethyl acrylate. A polyolefine may include one or more of polyethylene, polypropylene, polybutylene, polymethylpentene (and co-polymers thereof), polynorbomene (and co-polymers thereof), poly (f -butene), poly(3-methylbutene), poly(4- methylpentene) and copolymers of ethylene with propylene, f -butene, f -hexene, f -octene, 1- decene, 4-methyl-l -pentene and 1- octadecene.

The 3D printable material (and the 3D printed material) may comprise one or more of polycarbonate (PC), polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), polyoxymethylene (POM), polyethylene naphthalate (PEN), styrene- acrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), and semi- crystalline polytethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), poly(methyl methacrylate) (PMMA), polystyrene (PS), and styrene acrylic copolymers (SMMA).

The term 3D printable material is further also elucidated below, but especially refers to a thermoplastic material, optionally including additives, to a volume percentage of at maximum about 60 %, such as at maximum about 30 %, or at maximum 20 % (of the additives relative to the total volume of the thermoplastic material and additives).

The printable material may comprise two phases. The printable material may comprise a phase of printable polymeric material, especially thermoplastic material (see also below), which phase is especially an essentially continuous phase. In this continuous phase of thermoplastic material polymer additives such as one or more of antioxidant, heat stabilizer, light stabilizer, ultraviolet light stabilizer, ultraviolet light absorbing additive, near infrared light absorbing additive, infrared light absorbing additive, plasticizer, lubricant, release agent, antistatic agent, anti-fog agent, antimicrobial agent, colorant, laser marking additive, surface effect additive, radiation stabilizer, flame retardant, anti-drip agent may be present. The additive may have useful properties selected from optical properties, mechanical properties, electrical properties, thermal properties, and mechanical properties (see also above).

The printable material may comprise particulate material, i.e. particles embedded in the printable polymeric material, which particles form a substantially discontinuous phase. The number of particles in the total mixture is especially not larger than 60 vol.%, relative to the total volume of the printable material (including the (anisotropically conductive) particles) especially in applications for reducing thermal expansion coefficient. For optical and surface related effect number of particles in the total mixture is equal to or less than 20 vol.%, such as up to 10 vol.%, relative to the total volume of the printable material (including the particles). Hence, the 3D printable material especially refers to a continuous phase of essentially thermoplastic material, wherein other materials, such as particles, may be embedded. Likewise, the 3D printed material especially refers to a continuous phase of essentially thermoplastic material, wherein other materials, such as particles, are embedded. The particles may comprise one or more additives as defined above. Hence, the 3D printable materials may comprise particulate additives.

The printable material is printed on a receiver item. Especially, the receiver item can be the building platform or can be comprised by the building platform. The receiver item can also be heated during 3D printing. However, the receiver item may also be cooled during 3D printing.

The phrase “printing on a receiver item” and similar phrases include amongst others directly printing on the receiver item, or printing on a coating on the receiver item, or printing on 3D printed material earlier printed on the receiver item. The term “receiver item” may refer to a printing platform, a print bed, a substrate, a support, a build plate, or a building platform. Instead of the term “receiver item” also the term “substrate” may be used. The phrase “printing on a receiver item” and similar phrases include amongst others also printing on a separate substrate on or comprised by a printing platform, a print bed, a support, a build plate, or a building platform. Therefore, the phrase “printing on a substrate” and similar phrases include amongst others directly printing on the substrate or printing on a coating on the substrate or printing on 3D printed material earlier printed on the substrate. Here below, further the term substrate is used, which may refer to a printing platform, a print bed, a substrate, a support, a build plate, or a building platform, or a separate substrate thereon or comprised thereby.

Layer by layer printable material is deposited, by which the 3D printed item is generated (during the printing stage). The 3D printed item may show a characteristic ribbed structures (originating from the deposited filaments). However, it may also be possible that after a printing stage, a further stage is executed, such as a finalization stage. This stage may include removing the printed item from the receiver item and/or one or more post processing actions. One or more post processing actions may be executed before removing the printed item from the receiver item and/or one more post processing actions may be executed after removing the printed item from the receiver item. Post processing may include one or more of polishing, coating, and adding a functional component. Post-processing may include smoothening the ribbed structures, which may lead to an essentially smooth surface.

In 3D printing, layers may be deposited on top of each other to provide a stack of layers. It may also be possible to deposit layers next to each other. Hence, instead of a stack of single layers, it may also be possible to provide a stack of n layers. Hence, a stack of layers may be defined of (n · m) layers, wherein the number of n layers are the layers in a single plane or level, and wherein the number m indicates the number of layers or layer levels on top of each other. Hence, when 3D printing in fact layer level after layer level is printed, with the latter being printed on the former, thereby providing a stack of (m) layer levels. Each layer level may comprise one or more layers (i.e. n layers). The number of layers within the levels may differ, though this may depend upon the width of the layers and also on the width of lower layers (with reference to the print direction or stacking direction) and may also depend on the shape of the 3D item.

A 3D item may comprise parts, like walls, which may comprise a stack of layer levels, with each layer level comprising one or more layers.

It may be interesting to vary a width of the layer levels along the stacking direction. This can be done by varying the width of the layers and/or this may be done by varying the number of layers in the layer levels. For instance, a number of layer levels alternated with a wider layer level may provide additional strength to the 3D item. Further, such structure may allow specific optical effects.

One or more layers of different levels may comprise additives, such as particles, to create optical effects. Hence, amongst others the method may comprise a 3D printing stage comprising layer-wise depositing 3D printable material, to provide the 3D item comprising 3D printed material (on a receiver item), wherein the 3D item comprises a plurality of layers of 3D printed material, wherein the plurality of layers comprise particle comprising layers. Hence, not necessarily all layers of the 3D printed item are particle comprising layers. However, at least two layers may be particle comprising layers. Therefore, the stack may comprise a plurality of layer levels, wherein at least two layer levels comprise additive comprising layers, especially particle comprising layer, and wherein the two or more layer levels comprising additive comprising layers may each comprise one or more additive comprising layers and optionally one or more non-particle comprising layers.

A layer level may be defined as one or more layers at the same (stacking) height, wherein all layers are parallel to one another. Layer levels may not comprise particles. Alternatively, layer levels may comprise particles. Such layer levels that comprise particles may be referred to as particle comprising layer levels.

Such additives may be one or more of (i) reflective for light, (ii) light absorbing, (iii) transmissive for light, and (iv) luminescent. However, would there be a variation in layer level thickness, this may have impact on the optical properties of the respective layer levels. For instance, it may be that the scattering is larger at the thicker layer levels or the transmission is lower at the thicker layer levels.

Assuming two or more layer levels, with one layer level comprising layers and one layer level comprising n ₂ layers, it may thus be that n ₁ ≠ n ₂ . Assuming that both are at least one, it is not necessarily the case that when n ₁ is larger than 1 or n ₂ is larger than 1, the layers in the respective layer level both comprise the additives. Further, it is also possible that one or more of the layers comprise core-shell layers. Hence, to take account of the additives in the layer levels, herein a zone is defined wherein the additives are available, which zone in a single layer level may consist of two or more (sub)zones (when there are two or more layers in that level). The concentration of the additive in the zones and the accumulated with of the zones are herein especially of interest, as in first approximation they may substantially determine the optical properties of the layers based on the additive.

The 3D printed item may comprise a plurality of layers. One or more layers may comprise particles and may hence be referred to as particle comprising layers. Especially, the particle comprising layers may comprise particle comprising zones. The particle comprising zone may be defined as the zone of the particle comprising layer that comprises the particles. The particle comprising zone may consist of the layer. Alternatively, when the layer comprises a core-shell layer, the particles may be located in the core, or in the shell, or in both. In such examples, the zone may be defined by the core, the shell, or both, respectively.

Therefore, the particle comprising layers comprise particle comprising zones, wherein each particle comprising zone comprises particles at a particle concentration (C). As indicated above, the particle concentration may differ in different zones of different layers. The concentrations of zones in the same layer level may essentially be the same. Hence, concentration may differ between layer levels, but within layer levels, the concentrations may be the same.

In this way, during the 3D printing stage, a 3D item may be provided which comprises a stack of layer levels, wherein the stack has a stacking direction (S), wherein a plurality of the layer levels comprise particle comprising layer levels, each comprising one or more particle comprising layers. As indicated above, the particle comprising layer levels comprise an accumulated particle comprising zone width (W _A ) being the accumulated width of the one or more particle comprising zones of the one or more particle comprising layers, with the accumulated width (W _A ) defined perpendicular to the stacking direction (S). When 3D printing on a receiver item, the receiver item may be defined as the xy-plane. Perpendicular thereto, the 3D item is printed in the z-direction. This z-direction may be indicated the printing direction or stacking direction. The above-indicated ribbed structure will in general be parallel to the xy-direction with the stack of the ribs parallel to the stacking direction. Hence, the stacking direction (S) may be the direction from an earlier printed layer level towards a later printed layer level.

A layer comprising particles may thus define a zone which comprises the particles. In the case of a core-shell layer, this may be the core or the shell or both. In case of a non-core shell layer, especially an essentially homogeneous layer, the zone may essentially be the layer.

Herein, when a layer comprises an additive, this refers to at least part of a length of the layer. Hence, assuming a layer having a layer length L ₁ then at least part of the layer length comprises the particles (for particle comprising layers), and optionally a part of the layer along the length may not comprise particles. Hence, particle comprising layers may comprise a zone comprising particles. When two or more particle comprising layers are configured in the same layer level, then the accumulated particle comprising zone width may refer to the accumulated width of the two or more zones of the two or more particle comprising layers in the same layer level.

When over at least part of the length of the layer the layer comprises the additive, such as particles, then essentially the layer may consist (over that length) of the particle comprising zone. Therefore, one or more of the particle comprising layers may consist of a (respective) particle comprising zone.

All layer levels of the stack may comprise additive comprising layer levels (such as particle comprising layer levels). However, it is herein not excluded that the stack also comprises layer levels not comprising the additive.

Further, all layers within the layer levels of the stack may comprise additive comprising layers. However, it is herein also not excluded that one or more of the layers, even within the same additive comprising layer level, do not comprise the additive. Hence, at least two layer levels of the stack each comprise at least one additive comprising layer. Further, an additive comprising layer level comprise at least one additive comprising layer but may optionally also comprise one or more layers not comprising the additive.

For each additive comprising layer level the accumulated width (W _A ) is defined perpendicular to the stacking direction (S). As indicated above, at least two layer levels of the stack each comprise at least one additive comprising layer. However, also more than two layer levels of the stack may each comprise at least one additive comprising layer. The accumulated width (W _A ) of a first additive comprising layer level may be indicated as W _A1 , and the accumulated width (W _A ) of a second additive comprising layer level may be indicated as W _A2 . Hence, the accumulated width (W _A ) of an (respective) additive comprising layer level may be indicated as W _An . Here, n may indicate a number of a numbering of the additive comprising layer levels.

Therefore, each additive comprising layer level may comprise an accumulated additive comprising zone width (W _A ). which may be different for different additive comprising layer levels. Note that each accumulated additive comprising zone width (W _A ) may be defined by one or more zones, dependent upon the number of zones in the respective layer level.

Note that two neighboring additive comprising layer levels may touch each other. However, one or more layer levels without additive may be configured between the two neighboring additive comprising layer levels. Additive comprising layer levels and layer levels not comprising the additive may form a (regular) pattern or array. In the invention, in dependence of the zone width (accumulated particle comprising zone widths) the particle concentration may be controlled. Basically, there are two main options. In a first option, the concentration is decreased when the zone width increases. This may allow a compensation for the increase. In this way, the optical property differences over the 3D item may be limited or even essentially absent. In a second option, the concentration is increased when the zone width increases. This may allow or enhance specific optical effects and may allow a better spatial (power) distribution and/or spectral (power) distribution of the reflected light or a more intense luminescence at specific locations. Other options are not excluded. How the particle concentration may be controlled is further elucidated below.

The method may further comprise during the 3D printing stage increasing or decreasing the particle concentration (C) in the one or more particle comprising zones of the one or more particle comprising layers of each particle comprising layer levels depending on the accumulated particle comprising zone width (W _A ) of the particle comprising layer levels.

As indicated above, the particles may be one or more of (i) reflective for light, (ii) light absorbing, (iii) transmissive for light, and (iv) luminescent. When particles are applied, they are especially embedded in polymeric material (“polymeric matrix material”), thereby allowing the material to be 3D printable. Especially, the polymeric material as such is light transmissive. Hence, would the particles not be present, visible light may be transmitted through one or more of the layer levels, in a direction perpendicular to the stacking direction (and perpendicular to the layer level).

The particle comprising layers may comprise polymeric matrix material that is light transmissive, wherein the particle comprising layers further comprise an additive, especially a particulate additive, embedded in the polymeric matrix material, wherein the additive may be one or more of ( i) reflective for light, (ii) light absorbing, (iii) transmissive for light, and (iv) luminescent. More especially, the particle comprising layers may essentially consist of (a) polymeric matrix material that is light transmissive and (b) the additive, wherein additive, especially a particulate additive, is embedded in the polymeric matrix material, wherein the additive may be one or more of (i) reflective for light, (ii) light absorbing, (iii) transmissive for light, and (iv) luminescent.

The particles may be reflective for light. Here, the term light may refer to visible light, having one or more wavelengths in the visible wavelength range of 380 to 780 nm. When reflective particles are applied, the layer (levels) may be reflective. The reflectivity may be metal-like. The reflective particles may provide the layer (level) with a white color, for instance when the particles are one or more types selected from the group of TiO ₂ , BaSO ₄ , MgO, and AI ₂ O ₃ .

A light reflective layer (level) may have a light reflectivity in the range of 50 to 100 %, especially in the range of 70 to 100%, for light having a wavelength selected from the visible wavelength range. This may apply for a wavelength range of at least 100 nm, especially a wavelength range of at least 250 nm, such as a wavelength range of at least 300 nm (within the range of 380 to 780 nm).

Note that a material may be reflective for one or more first wavelengths and absorb one or more second wavelengths, which may be the case with colored material. The term “light reflective material” may herein especially refer to a white material or metallic reflective material, i.e. materials which have a relatively high reflection, such as at least 70 %, over a relatively high wavelength range, such as at least 100 nm, even more especially at least 250 nm, such as at least 300 nm, within the range of 380 to 780 nm.

Alternatively or additionally, the particles may be light absorbing. Again, the term light may especially refer to visible light, having one or more wavelengths in the visible wavelength range of 380 to 780 nm. When light absorbing particles are applied, the layer (levels) may be black, or may have a color. Here, the term absorbing may especially refer to colored or black particles, which may essentially not luminesce upon absorption of light in the visible.

A light absorbing layer (level) may have a light absorbance in the range of 50 to 100 %, especially in the range of 70 to 100%, for light having a wavelength selected from the visible wavelength range. As can be derived from the above, this may apply for a wavelength range of at least 100 nm, especially a wavelength range of at least 250 nm, such as a wavelength range of at least 300 nm (within the range of 380 to 780 nm). Herein, the term “light absorbing material” especially refers to a colored material or to a black material.

Additionally or alternatively, the particles may be transmissive for light. Again, the term light may especially refer to visible light, having one or more wavelengths in the visible wavelength range of 380 to 780 nm. When light transmissive particles are applied, for instance light scattering may be controlled. Hence, especially light transmissive particles may be applied in a light transmissive polymeric material, when they have different indices of refraction, like differing at least 0.02, such as at least 0.05, such as at least about 0.1. The light transmissive particle material may be an inorganic material or organic material.

Especially, the light transmissive particle material is chemically different from the polymeric matrix material. Additionally or alternatively, the particles may comprise a luminescent material (and may thereby be luminescent). In this case, the particles may be configured to for example absorb visible light or UV radiation, and convert the light/radiation into (especially) visible light. Again, the term light may especially refer to visible light, having one or more wavelengths in the visible wavelength range of 380 to 780 nm. UV radiation may refer to radiation having wavelengths selected from the range of 100 to 380 nm, herein especially selected from the range of 190 to 380 nm. The luminescent material may be an inorganic or organic luminescent material.

The term “luminescent material” especially refers to a material that can convert first radiation, especially one or more of UV radiation and blue radiation, into second radiation. In general, the first radiation and second radiation have different spectral power distributions. Hence, instead of the term “luminescent material”, also the terms “luminescent converter” or “converter” may be applied. In general, the second radiation has a spectral power distribution at larger wavelengths than the first radiation, which is the case in the so- called down-conversion. The second radiation may have a spectral power distribution with intensity at smaller wavelengths than the first radiation, which is the case in the so-called up- conversion.

The term “luminescent material” may refer to a material that can convert radiation into visible and/or infrared light. For instance, the luminescent material may be able to convert one or more of UV radiation and blue radiation into visible light. The luminescent material may also convert radiation into infrared radiation (IR). Hence, upon excitation with radiation, the luminescent material emits radiation. In general, the luminescent material will be a down converter, i.e. radiation of a smaller wavelength is converted into radiation with a larger wavelength (λ _ex < λ _em ), though the luminescent material may comprise an up- converter luminescent material so that radiation of a larger wavelength can be converted into radiation with a smaller wavelength (λ _ex > λ _em ).

The term “luminescence” may refer to phosphorescence or to fluorescence. Instead of the term “luminescence”, also the term “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. Likewise, the term “luminescent material” may refer to a phosphorescent material and/or to a fluorescent material.

The term “luminescent material” may also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are indicated below. Hence, the term “luminescent material” may refer to a luminescent material composition. The transmission T (or light permeability) can be determined by providing light at a specific wavelength with a first intensity I ₁ to the light transmissive material under perpendicular radiation and relating the intensity of the light I ₂ at that wavelength measured after transmission through the material, to the first intensity of the light provided at that specific wavelength to the material, thus T = I ₂ / I ₁ . Likewise, the reflectivity R can be determined by relating the intensity of the light I ₃ at that wavelength measured after reflection by the material, to the first intensity of the light I ₁ provided at that specific wavelength to the material. Thus R = I ₃ /I ₁ . The absorbance A may be defined as A = 1 — (T + R) (see also E-208 and E-406 of the CRC Handbook of Chemistry and Physics, 69th edition, 1088-1989).

A material may be considered transmissive when the transmission of the radiation at a wavelength or in a wavelength range is larger than the reflectivity and absorbance (at that wavelength or in that wavelength range), thus when T > R and T > A, especially wherein T/R ≥ 1.2 and T/A ≥ 1.2. A material may be considered reflective when the reflectivity of the radiation at a wavelength or in a wavelength range is larger than the transmission and absorbance (at that wavelength or in that wavelength range), thus when R > T and R > A, especially wherein R/T ≥ 1.2 and R/A ≥ 1.2. A material may be considered absorbing when the absorbance of the radiation at a wavelength or in a wavelength range is larger than the transmission and reflectivity (at that wavelength or in that wavelength range), thus when A > T and A > R, especially wherein A/T ≥ 1.2 and A/R ≥ 1.2. Here, T, R, and A refer to percentages.

A material may be considered transmissive when the transmission of the radiation at a wavelength or in a wavelength range, especially at a wavelength or in a wavelength range of radiation generated by a source of radiation as herein described, through a 1 mm thick layer of the material, especially even through a 5 mm thick layer of the material, under perpendicular irradiation with said radiation is at least about 20 %, such as at least 40 %, like at least 60 %, such as especially at least 8 0%, such as at least about 85 %, such as even at least about 90 %.

The light transmissive material has light guiding or wave guiding properties. Hence, the light transmissive material is herein also indicated as waveguide material or light guide material. The light transmissive material will in general have (some) transmission of one or more of (N)UV, visible and (N)IR radiation, such as at least visible light, in a direction perpendicular to the length of the light transmissive material. The transmission of the light transmissive material (as such) for one or more luminescence wavelengths may be at least 80 % per cm, such as at least 90 % per cm, or at least 95%per cm, or at least 98 % per cm, or at least 99 % per cm. This implies that, for example, a cube of light transmissive material of 1 cm ³ , under perpendicular irradiation of radiation having a selected luminescence wavelength (such as a wavelength corresponding to an emission maximum of the luminescence of the luminescent material of the light transmissive material), will have a transmission of at least 95 %.

Herein, values for transmission especially refer to transmission without taking into account Fresnel losses at interfaces (for example with air). Hence, the term “transmission” especially refers to the internal transmission. The internal transmission may be determined by measuring the transmission of two or more bodies having a different width over which the transmission is measured. Then, based on such measurements the contribution of Fresnel reflection losses and (consequently) the internal transmission can be determined. Hence, especially, the values for transmission indicated herein, disregard Fresnel losses.

An anti-reflection coating may be applied to the luminescent body, such as to suppress Fresnel reflection losses (during the light incoupling process).

In addition to a high transmission for the wavelength(s) of interest, also the scattering for the wavelength(s) may especially be low. Hence, the mean free path for the wavelength of interest only taking into account scattering effects (thus not taking into account possible absorption may be at least 0.5 times the length of the body, such as at least the length of the body, like at least twice the length of the body. For instance, the mean free path only taking into account scattering effects may be at least 5 mm, such as at least 10 mm. The wavelength of interest may especially be the wavelength at maximum emission of the luminescence of the luminescent material. The term “mean free path” is especially the average distance a ray will travel before experiencing a scattering event that will change its propagation direction.

The element comprising the light transmissive material may essentially consist of the light transmissive material. The element comprising the light transmissive material may be a light transparent element. Especially, the light transmittance is similar for all wavelengths in the visible wavelength range.

The light transmissive element, such as the light transparent element, may have an absorption length and/or a scatter length of at least the length (or thickness) of the light transmissive element, such as at least twice the length of the light transmissive element. The absorption length may be defined as the length over which the intensity of the light along a propagation direction due to absorption drops with 1/e. Likewise, the scatter length may be defined as the length along a propagation direction along which light is lost due to scattering and drops thereby with a factor 1/e. Here, the length may thus especially refer to the distance between a first face and a second face of the light transmissive element, with the light transmissive material configured between the first face and second face.

Herein, when an element is indicated to be transmissive this may imply that at one or more wavelengths the part of the radiation that is transmitted may be larger than the part of the radiation that is reflected or absorbed. Herein, when an element is indicated to be reflective this may imply that at one or more wavelengths the part of the radiation that is reflected may be larger than the part of the radiation that is transmitted or absorbed.

As indicated above, the invention is not limited to particles as additive. Hence, the additive may comprise an organic pigment or organic dye (or other organic non- polymeric material providing a function selected from one or more of (i) reflective for light, (ii) light absorbing, (iii) transmissive for light, and (iv) luminescent. Such organic material, like a dye or pigment, may be molecularly dispersed in the polymeric matrix of the 3D printable material or 3D printed material.

The particles (“particulate material”) may be selected from particles and flakes. Also combinations may be applied.

As indicated above, with the invention the concentration of the additive may be controlled in relation to the thickness of the levels, or more especially in relation to the thickness of the accumulated particle comprising zone widths. Hence, the 3D item may comprise a layer stack wherein two or more layer levels may have two or more different accumulated particle comprising zone widths. Therefore, the 3D item may comprise a layer stack wherein two or more layer levels may have two or more different widths.

The 3D printing stage may comprise providing two or more particle comprising layer levels having different accumulated particle comprising zone widths (W _A ). More especially, the 3D printing stage may comprise providing two or more particle comprising layer levels having different layer widths (W _L ). The layer widths may be the accumulated width of the layers in the layer level.

As indicated above, when the accumulated particle comprising zone width is increased, the particle concentration may be decreased. However, when the accumulated particle comprising zone width is increased, the particle concentration may also be increased.

It may be desirable to control one or more of reflectivity of the layer levels and/or transmissivity of the layer levels. Yet, it may be desirable to control one or more of reflectivity of the layer levels. Therefore, the method may comprise controlling reflectivity of the plurality of particle comprising layer levels by increasing or decreasing the particle concentration (C) in the one or more particle comprising zones of the particle comprising layer levels depending on the accumulated particle comprising zone width (W _A ) of the particle comprising layer levels.

The particles may comprise light reflective particles, and the reflectivity of one or more particle comprising layer levels may be in the range from 30 % to 80 %.

The particle concentration may be controlled in different way. For instance, the 3D printable material that may be fed to the printer head may be provided by two or more sources of 3D printable material having different concentration of additive. At least one of the two or more sources of 3D printable material should comprise such additives, and another one may not comprise such additives. This allows a scaling from zero to the concentration of the one of the two or more sources of 3D printable material that should comprise such additives. A control system (see also below) may control the relative contributions of the 3D printable materials. Therefore, the method may comprise controlling the particle concentration (C) in the one or more particle comprising zones of the particle comprising layer levels by providing during at least part of the printing stage two or more types of printable material comprising different particle concentrations (C) to a printing head and controlling the relative flux of each type of printable material.

Alternatively or additionally, a core-shell solution may be chosen. When the 3D printable material for the core and the 3D printable material for the shell have different concentrations of the additive, also the concentration in the zone(s) may be controlled. Especially, this may be applied when the relative outflows of the core material and shell material may be controlled. This might imply that there is complete variability from a layer consisting of only shell material, via a core-shell layer, to a layer consisting of only core material. When controlling the relative outflows, the thickness of the shell and the core can be controlled. Especially, however, to one or more of the shell part of the nozzle or the core part of the nozzle, two 3D printable may be provided, having different concentrations of the additive, such as of the particles, with the influx (and thus the outflow) of the respective material being controlled.

For instance, the 3D printable material that may be fed to the printer head may be provided by two or more sources of 3D printable material having different concentration of additive to the core and one or more shell parts of the printer head (or nozzle). At least one of the two or more sources of 3D printable material should comprise such additives, and another one may not comprise such additives. This allows a scaling from zero to the concentration of the one of the two or more sources of 3D printable material should comprise such additives. A control system (see also below) may control the relative contributions of the 3D printable materials. Hence, during at least part of the 3D printing stage the 3D printable material may comprise 3D printable core material and 3D printable shell material, to provide the 3D item comprising a core-shell layer of 3D printed material, wherein the 3D printed material comprises a core comprising 3D printed core material and a shell comprising 3D printed shell material, wherein the shell at least partly encloses the core, wherein one or more of the core and shell define the particle comprising zone. When only the 3D printable core material and thus the 3D printed core material comprises particles, the core may define the particle comprising zone. When only the 3D printable shell material and thus the 3D printed shell material comprises particles, the shell may define the particle comprising zone.

As indicated above, the concentration may be reduced when the accumulated particle comprising zone width increases. This may allow an essentially constant reflectivity or transmissivity. Hence, the concentration in of the additive in the zones may be negatively mathematically related to the accumulated particle comprising zone width. Hence, the 3D printing stage may comprise a first stage providing a first accumulated particle comprising zone width (W _A1 ) and a first particle concentration (C ₁ ) for a first particle comprising layer level, and a second stage having a second accumulated particle comprising zone width (W _A2 ) and a second particle concentration (C ₂ ) for a second particle comprising layer level, wherein 0.5 ≤ (W _A1 .C ₁ )/(W _A2 · C ₂ ) ≤ 2, such as 0.8 ≤ (W _A1 · C ₁ )/(W _A2 · C ₂ ) ≤ 1.25.

Further, W _A1 may be larger than W _A2 , such as W _A1 ≥ 1.1 · W _A2 , or W _A1 ≥ 1.2 · W _A2 , or W _A1 ≥ 1-3 · W42 • Yet further, the layer level width W _L1 of the first layer level may be larger than the layer width W _L21 of the second layer level. Hence, W _L1 > W _L2 , such as W _L1 ≥ 1.1 · W _L2 , or W _L1 ≥ 1.2 · W _L2 , or W _L1 ≥ 1.3 · W _L2 . The aforementioned conditions are defined by referring to two layer levels. However, they may of course apply to more than two layer levels.

As indicated above, the reflectivity may essentially be kept constant in this way. Hence, a first particle comprising layer level may comprise a first accumulated particle comprising zone width (W _A1 ) and a first reflectivity (R ₁ ), and a second particle comprising layer level may comprise a second accumulated particle comprising zone width (W _A2 ) and a second reflectivity (R ₂ ), wherein W _A1 > W _A2 (especially wherein W _A1 ≥ 1.2 · W _A2 , ^see also above), wherein 0.8 ≤ R ₁ /R ₂ ≤ 1.2, such as wherein 0.9 ≤ R ₁ /R ₂ ≤ 1.1. Further, a first particle comprising layer level may comprise a first layer level width (Vl/ _L1 ) and a first reflectivity (R ₁ ), and a second particle comprising layer level may comprise a second layer level width (W _L2 ) and a second reflectivity (R ₂ ), wherein W _L1 > W _L2 (especially, wherein W _L1 ≥ 1.2 · W _L2 , see also above), wherein 0.8 ≤ R ₁ /R ₂ ≤ 1.2, especially wherein 0.9 ≤ R ₁ /R ₂ ≤ 1.1. However, this may of course apply to more than two layer levels.

Some pairs of variables are related positively (“mathematically positively related”). This means that as one variable goes up, the other tends to go up as well. Other pairs are negatively related (“mathematically negatively related”), which means that as one goes down the other tends to go up. Non-limiting examples of positive relations are y = a · x, or y = x ² , or y = a · log(x), wherein a > 0 and x > 0; non-limiting examples of negative relations are y = a/x or y = b · x, or y = b · x ² , or y = 1/ x ² , or y = b · log(x), wherein a > 0 and b < 0 and x > 0.

As indicated above, the concentration may be increased when the accumulated particle comprising zone width increases. This may allow an additional optical effect. Hence, the concentration of the additive in the zones may be positively mathematically related to the accumulated particle comprising zone width. Hence, the 3D printing stage may comprise a first stage comprising providing a first particle comprising layer level having a first accumulated particle comprising zone width (W _A1 ) and a first particle concentration (C ₁ ), and a second stage comprising providing a second particle comprising layer level having a second accumulated particle comprising zone width (W _A2 ) and a second particle concentration (C ₂ ), wherein 0.5 ≤ (W _A1 · C ₂ )/(W _A2 · C ₁ ) ≤ 2, such as wherein 0.8 ≤ (W _A1 • C ₂ )/(W _A2 · C ₁ ) ≤ 1.25.

Further, W _A1 may be larger than W _A2 , such as W _A1 ≥ 1.1 · W _A2 , or W _A1 ≥ 1.2 ·W _A2 , or W _A1 ≥ 1.3 · W _A2 . Yet further, the layer level width W _L1 of the first layer level may be larger than the layer width W _L2 of the second layer level. Hence, W _L1 > W _L2 , such as W _L1 ≥ 1.1 · W _L2 , or W _L1 ≥ 1.2 · W _L2 , or W _L1 ≥ 1.3 · W _L2 . The aforementioned conditions are defined by referring to two layer levels. However, they may of course apply to more than two layer levels.

Therefore, W _A1 may be equal to or larger than 1.1 · W _A2 , such as W _A1 ≥ 1.2 ·W _A2 , or W _A1 ≥ 1.3 · W _A2 • Further, W/ _L1 may be equal to or larger than 1.1 · W _L2 , such as W _L1 ≥ 1.2 · W _L2 , or W _L1 ≥ 1.3 - W _L2 .

In a second aspect, the invention provides a computer program product that, when running on a computer which is functionally coupled to or comprised by a fused deposition modeling 3D printer, is capable of bringing about the method as according to the first aspect.

In a third aspect, the invention provides a 3D printed item obtainable with the method according to the first aspect. The 3D item comprises a 3D printed material. The 3D item has a stack of layer levels in a stacking direction. The layer levels have two or more additive comprising layer levels, each additive comprising layer level having one or more additive comprising layers. Each additive comprising layer has an additive comprising zone with an additive at an additive concentration, the additive being one or more of (i) reflective for light, (ii) light absorbing, (iii) transmissive for light, and (iv) luminescent. Each additive comprising layer level has an accumulated additive comprising zone width, being the accumulated width of the additive comprising zones of the additive comprising layers in a direction perpendicular to the stacking direction. The two or more additive comprising layer levels have different accumulated additive comprising zone widths, the additive concentration in one additive comprising zone of the two or more additive comprising layer levels being increased or decreased relative to the additive concentration in another additive comprising zone of the two or more additive comprising layer levels.

The 3D printed item may comprise a plurality of layers on top of each other, i.e. stacked layers. The width (thickness) and height of (individually 3D printed) layers may be selected from the range of 100 to 5000 μm, such as 200 to 2500 μm, with the height in general being smaller than the width. For instance, the ratio of height and width may be equal to or smaller than 0.8, such as equal to or smaller than 0.6.

Layers may be core-shell layers or may consist of a single material. Within a layer, there may also be a change in composition, for instance when a core-shell printing process was applied and during the printing process it was changed from printing a first material (and not printing a second material) to printing a second material (and not printing the first material).

At least part of the 3D printed item may include a coating.

Some specific aspects in relation to the 3D printed item according to the third aspect have already been elucidated when discussing the method according to the first aspect. Below, some specific aspects in relation to the 3D printed item are discussed in more detail.

As indicated above, the 3D item may comprise a first particle comprising layer level having a first accumulated particle comprising zone width (W _A1 ) and a first particle concentration (C ₁ ), and a second particle comprising layer level having a second accumulated particle comprising zone width (W _A2 ) and a second particle concentration (C ₂ ). wherein 0.5 ≤ (W _A1 · C ₁ )/(W _A2 · C ₂ ) ≤ 2, such as 0.8 ≤ (W _A1 · C ₁ )/(W _A2 • C ₂ ) ≤ 1.25. Further, may be larger than W _A2 , such as W _A1 ≥ 1.1 · W _A2 , or W _A1 ≥ 1.2 · W _A2 , or W _A1 ≥ 1.3 · W _A2 .

Yet further, the layer level width W _L1 of the first layer level may be larger than the layer width W _L21 of the second layer level. Hence, W _L1 > W _L2 , such as W _L1 ≥ 1.1 · W _L2 , or W _L1 ≥ 1.2 · W/ _L2 , or W _L1 ≥ 1.3 · W _L2 . The aforementioned conditions are defined by referring to two layer levels. However, they may apply to more than two layer levels.

A first particle comprising layer level may comprise a first accumulated particle comprising zone width (W _A1 ) and a first reflectivity (R ₁ ), and a second particle comprising layer level may comprise a second accumulated particle comprising zone width (W _A2 ) and a second reflectivity (R ₂ ), wherein 0.8 ≤ R ₁ /R ₂ ≤ 1.2, such as wherein 0.9 ≤ R ₁ /R ₂ ≤ 1.1. Especially, W _A1 may be larger than W _A2 , such as W _A1 ≥ 1.1 · W _A2 , or W _A1 ≥ 1.2 · W _A2 , or W _A1 ≥ 1.3 · W _A2 .

Yet further, the 3D item may comprise a first particle comprising layer level having a first accumulated particle comprising zone width (W _A1 ) and a first particle concentration (C ₁ ), and a second particle comprising layer level having a second accumulated particle comprising zone width (W _A2 ) and a second particle concentration (C ₂ ), wherein 0.5 ≤ (W _A1 · C ₂ )/(W _A2 • C ₁ ) ≤ 2, such as wherein 0.8 ≤ (W _A1 · C ₂ )/(W _A2 • C ₁ ) ≤ 1.25. Further, W _A1 may be larger than W _A2 , such as W _A1 > 1.1 · W _A2 , or W _A1 ≥ 1.2 · W _A2 , or W _A1 ≥ 1.3 · W _A2 .

Yet further, the layer level width W _L1 of the first layer level may be larger than the layer width W _L2 of the second layer level. Hence, W _L1 > W _L2 , such as W _L1 ≥ 1.1 · W _L2 , or W _L1 ≥ 1.2 · W _L2 , or W _L1 ≥ 1.3 · W _L2 . The aforementioned conditions are defined by referring to two layer levels. However, they may apply to more than two layer levels.

The 3D printed item that can be obtained with the method described herein may be functional per se. For instance, the 3D printed item may be a lens, a collimator, or a reflector. The thus obtained 3D item may (alternatively) be used for decorative or artistic purposes. The 3D printed item may include or be provided with a functional component. The functional component may especially be selected from the group consisting of an optical component, an electrical component, and a magnetic component. The term “optical component” especially refers to a component having an optical functionality, such as a lens, a mirror, a light transmissive element, or an optical filter. The term “optical component” may also refer to a light source (like a LED). The term “electrical component” may refer to an integrated circuit, PCB, a battery, a driver, but also a light source (as a light source may be considered an optical component and an electrical component). The term “magnetic component” may refer to a magnetic connector or a coil. Alternatively, or additionally, the functional component may comprise a thermal component (for example configured to cool or to heat an electrical component). Hence, the functional component may be configured to generate heat or to scavenge heat.

As indicated above, the 3D printed item maybe used for different purposes. Amongst others, the 3D printed item maybe used in lighting. Hence, in yet a further aspect the invention also provides a lighting device comprising the 3D item as defined herein. In a specific aspect the invention provides a lighting system comprising (a) a light source configured to provide (visible) light source light and (b) the 3D item as defined herein, wherein 3D item may be configured as one or more of (i) at least part of a housing, (ii) at least part of a wall of a lighting chamber, and (iii) a functional component, wherein the functional component may be selected from the group consisting of an optical component, a support, an electrically insulating component, an electrically conductive component, a thermally insulating component, and a thermally conductive component. Hence, the 3D item may be configured as one or more of (i) at least part of a lighting device housing, (ii) at least part of a wall of a lighting chamber, and (iii) an optical element. As a relative smooth surface may be provided, the 3D printed item may be used as mirror or lens. The 3D item may be configured as shade. A device or system may comprise a plurality of different 3D printed items, having different functionalities.

Returning to the 3D printing process, a specific 3D printer may be used to perform the method according to the first aspect, and to provide the 3D printed item according to the third aspect. Such a specific 3D printer may be a fused deposition modeling 3D printer, comprising (a) a printer head comprising a printer nozzle, and (b) a 3D printable material providing device configured to provide 3D printable material to the printer head, wherein the fused deposition modeling 3D printer is configured to provide the 3D printable material to the printer head, wherein the fused deposition modeling 3D printer is configured to control the relative flux of the one or more types of 3D printable material to a substrate, thereby providing a 3D item comprising 3D printed material, wherein at least one of the types of 3D printable material comprises particles at a particle concentration (C). wherein the fused deposition modeling 3D printer further comprises (d) a control system, wherein the control system may especially be configured to execute the method according to the first aspect.

The printer nozzle may include a single opening. The printer nozzle may be of the core-shell type, having two (or more) openings. The term “printer head” may also refer to a plurality of (different) printer heads; hence, the term “printer nozzle” may also refer to a plurality of (different) printer nozzles.

The 3D printable material providing device may provide a filament comprising 3D printable material to the printer head or may provide the 3D printable material as such, with the printer head creating the filament comprising 3D printable material. Hence, the invention provides a fused deposition modeling 3D printer, comprising (a) a printer head comprising a printer nozzle, and (b) a filament providing device configured to provide a filament comprising 3D printable material to the printer head, wherein the fused deposition modeling 3D printer is configured to control the relative flux of the one or more types of 3D printable material to a substrate, thereby providing a 3D item comprising 3D printed material, wherein at least one of the types of 3D printable material comprises particles at a particle concentration (C), wherein the fused deposition modeling 3D printer further comprises (d) a control system, wherein the control system may especially be configured to execute the method as defined herein.

The 3D printer comprises a controller (or is functionally coupled to a controller) that is configured to execute in a controlling mode (or “operation mode”) the method as described herein. Instead of the term “controller” also the term “control system” may be used.

The term “controlling”, and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may refer to imposing behavior to the element (determining the behavior or supervising the running of an element), such as measuring, displaying, actuating, opening, shifting, and changing temperature. Beyond that, the term “controlling”, and similar terms may additionally include monitoring. Hence, the term “controlling”, and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. The control system and element may not be physically coupled. Control can be done via wired and/or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface. The control system may also be configured to receive and execute instructions form a remote control. The control system may be controlled via an app on a device, such as a portable device, like a smartphone, an iPhone, or a tablet. The device is thus not necessarily coupled to the lighting system but may be (temporarily) functionally coupled to the lighting system.

The control system may be configured to be controlled by an app on a remote device. The control system of the lighting system may be a slave control system or control in a slave mode. For instance, the lighting system may be identifiable with a code, especially a unique code for the respective lighting system. The control system of the lighting system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (for example QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, WiFi, LiFi, ZigBee, BLE or WiMAX, or another wireless technology.

The system, or apparatus, or device may execute an action in a “mode” or “operation mode” or “mode of operation”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operation mode” or “mode of operation” or “operational mode”. The term “mode” may also be indicated as “controlling mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed.

However, a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e. “on”, without further tunability).

The control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and/or a predetermined time scheme.

Instead of the term “fused deposition modeling (FDM) 3D printer” shortly the terms “3D printer”, “FDM printer” or “printer” may be used. The printer nozzle may also be indicated as “nozzle” or sometimes as “extruder nozzle”. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figs, 1a-1c schematically depict some general aspects of a 3D printer and of a 3D printed material;

Figs. 2a-2b schematically depict some aspects;

Figs. 3a-3b also schematically depict some aspects;

Figs. 4a-4b schematically depicts some applications. The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. la schematically depicts some aspects of the 3D printer. Reference 500 indicates a 3D printer. Reference 530 indicates the functional unit configured to 3D print, especially FDM 3D printing; this reference may also indicate the 3D printing stage unit. Here, only the printer head for providing 3D printed material, such as an FDM 3D printer head is schematically depicted. Reference 501 indicates the printer head. The 3D printer of the present invention may especially include a plurality of printer heads (see below). Reference 502 indicates a printer nozzle. The 3D printer of the present invention may especially include a plurality of printer nozzles. Reference 320 indicates a filament of printable 3D printable material (such as indicated above). For the sake of clarity, not all features of the 3D printer have been depicted, only those that are of especial relevance for the present invention (see further also below). Reference 321 indicates extrudate (of 3D printable material 201).

The 3D printer 500 is configured to generate a 3D item 1 by lay er- wise depositing on a receiver item 550, which may at least temporarily be cooled, a plurality of layers 322 wherein each layers 322 comprises 3D printable material 201, such as having a melting point Tm. The 3D printable material 201 may be deposited on a substrate 1550 (during the printing stage). By deposition, the 3D printable material 201 has become 3D printed material 202. 3D printable material 201 escaping from the nozzle 502 is also indicated as extrudate 321. Reference 401 indicates thermoplastic material.

The 3D printer 500 may be configured to heat the filament 320 material upstream of the printer nozzle 502. This may be done with a device comprising one or more of an extrusion and/or heating function. Such device is indicated with reference 573 and is arranged upstream from the printer nozzle 502 (i.e. in time before the filament material leaves the printer nozzle 502). The printer head 501 may include a liquefier or heater.

Reference 201 indicates printable material. When deposited, this material is indicated as (3D) printed material, which is indicated with reference 202.

Reference 572 indicates a spool or roller with material, especially in the form of a wire, which may be indicated as filament 320. The 3D printer 500 transforms this in an extrudate 321 downstream of the printer nozzle which becomes a layer 322 on the receiver item or on already deposited printed material. In general, the diameter of the extrudate 321 downstream of the nozzle 502 is reduced relative to the diameter of the filament 322 upstream of the printer head 501. Hence, the printer nozzle is sometimes indicated as extruder nozzle. Arranging layer 322 by layer 322 and/or layer 322t on layer 322, a 3D item 1 may be formed. Reference 575 indicates the filament providing device, which here amongst others include the spool or roller and the driver wheels, indicated with reference 576.

Reference A indicates a longitudinal axis or filament axis.

Reference 300 schematically depicts a control system, such as especially a temperature control system configured to control the temperature of the receiver item 550. The control system 300 may include a heater which is able to heat the receiver item 550 to at least a temperature of 50 °C, but especially up to a range of about 350 °C, such as at least 200 °C.

Alternatively or additionally, the receiver plate may also be moveable in one or two directions in the xy-plane (horizontal plane). Further, alternatively, or additionally, the receiver plate may also be rotatable about z-axis (vertical). Hence, the control system may move the receiver plate in one or more of the x-direction. y-direction, and z-direction.

Alternatively, the printer can have a head can also rotate during printing. Such a printer has an advantage that the printed material cannot rotate during printing.

Layers are indicated with reference 322 and have a layer height H and a layer width W.

Note that the 3D printable material is not necessarily provided as filament 320 to the printer head. Further, the filament 320 may also be produced in the 3D printer 500 from pieces of 3D printable material.

Reference D indicates the diameter of the nozzle (through which the 3D printable material 201 is forced). Reference S indicates the stacking direction. Note that a layer 322 may in fact define a plane, parallel to the layer, and perpendicular to the xy-plane formed by local stacking directions.

Fig. lb schematically depicts in 3D in more detail the printing of the 3D item 1 under construction. Here, in this schematic drawing the ends of the filaments 321 in a single plane are not interconnected, though in reality this may be the case.

Reference H indicates the height of a layer. Layers are indicated with reference 203. Here, the layers have an essentially circular cross-section. Often, however, they may be flattened, such as having an outer shape resembling a flat oval tube or flat oval duct (i.e. a circular shaped bar having a diameter that is compressed to have a smaller height than width, wherein the sides (defining the width) are (still) rounded).

Hence, Figs, la-lb schematically depict some aspects of a fused deposition modeling 3D printer 500, comprising (a) a first printer head 501 comprising a printer nozzle 502, (b) a filament providing device 575 configured to provide a filament 321 comprising 3D printable material 201 to the first printer head 501, and optionally (c) a receiver item 550. In Figs, la-lb, the first or second printable material or the first or second printed material are indicated with the general indications printable material 201 and printed material 202, respectively. Directly downstream of the nozzle 502, the filament 321 with 3D printable material becomes, when deposited, layer 322 with 3D printed material 202.

Fig. 1c schematically depicts a stack of 3D printed layers 322, each having a layer height H and a layer width W. Note that the layer width and/or layer height may differ for two or more layers 322. Reference 252 in Fig. 1c indicates the item surface of the 3D item (schematically depicted in Fig. 1c).

Referring to Figs, la-lc, the filament of 3D printable material that is deposited leads to a layer having a height H (and width W). Depositing layer 322 after layer 322, the 3D item 1 is generated. Fig. 1c very schematically depicts a single-walled 3D item 1.

Fig. 1c schematically depict general layers. Figs. 2a-3a schematically depict some specific aspects.

Figs. 2a-2b schematically depicts a 3D item 1 comprising 3D printed material 202. The 3D item 1 comprises a plurality of layers 322 of 3D printed material 202.

The plurality of layers 322 comprise particle comprising layers 2322.

Especially, the particle comprising layers 2322 comprise particle comprising zones 400. Each particle comprising zone 400 comprises particles 410 at a particle concentration C. Note that C is a general indication of the concentration. Different zones may have different concentration.

The particles 410 may be one or more of reflective for light, light absorbing, transmissive for light, and luminescent.

The 3D item 1 may comprise a stack 23 of layer levels 323. The stack 23 has a stacking direction S. A plurality of the layer levels 323 may comprise particle comprising layer levels 2323, each comprising one or more particle comprising layers 2322.

In the schematically depicted examples, all layer levels 323 of the stack 23 comprise additive comprising layer levels 2323 (such as particle comprising layer levels 2323). However, it is herein not excluded that the stack 23 also comprises layer levels 323 not comprising the additive.

Further, in the schematically depicted examples, all layers 322 within the layer levels 323 of the stack comprise additive comprising layers 2322. However, it is herein also not excluded that one or more of the layers 323 comprise additive comprising layers 2322 and optionally one or more of the layers 323 within the same additive comprising layer level 2323 do not comprise the additive (i.e. non additive comprising layers).

Especially, the particle comprising layer levels 2323 comprise an accumulated particle comprising zone width W _A being the accumulated width of the one or more particle comprising zones 400 of the one or more particle comprising layers 2322. The accumulated width W _A is defined perpendicular to the stacking direction S.

The 3D item 1 comprises two or more particle comprising layer levels 2323 having different accumulated particle comprising zone widths W _A . Further, the particle concentration C in the one or more particle comprising zones 400 of the one or more particle comprising layers 2322 of the particle comprising layer levels 2323 may be increased or decreased relative to another of the two or more particle comprising layer levels 2323.

Fig. 2a schematically depicts all layer levels 2323 having a single particle comprising layer 2322.

Fig. 2b schematically depict some layer levels 2323, indicated with reference 2323’, having more than one particle comprising layer 2322, and some layer levels, indicated with reference 2323”, having a single particle comprising layer 2322. Of course, other difference in the stack may also be possible.

Fig. 2b schematically depicts two examples. In example 1, C ₁ < C ₂ , whereasW _A1 > W _A2 . In example II, C ₁ > C ₂ ,and W _A1 > W _A2 . Further, in both examples, the layer level width W _L1 of the first layer level, indicated with reference 2323’, may be larger than the layer width W _L2 of the second layer level, indicated with reference 2323”. Hence, W _L1 may be larger than W _L2 , especially W _L1 ≥ 1.1 · W _L2 , even more especially wherein W _L1 ≥ 1.2 · W _L2 . The aforementioned options are defined by referring to two layer levels. However, they may apply to more than two layer levels, such as also schematically depicted in Fig. 2b.

Hence, the 3D item 1 may comprise a first particle comprising layer level 2323, indicated with reference 2323’, having a first accumulated particle comprising zone width WAI and a first particle concentration C1, and a second particle comprising layer level 2323, indicated with reference 2323”, having a second accumulated particle may comprise zone width W _A2 and a second particle concentration C ₂ . Especially, in examples 0.5 ≤ (W _A1 • C ₁ )/(W _A2 · C ₂ ) ≤ 2.

For instance, a first particle comprising layer level 2323, indicated with reference 2323’, may comprise a first accumulated particle comprising zone width W _A1 and a first reflectivity R ₁ , and a second particle comprising layer level 2323, indicated with reference 2323”, may comprise a second accumulated particle comprising zone width W _A2 and a second reflectivity R ₂ , wherein W _A1 > W _A2 , and wherein 0.8 ≤ R ₁ /R ₂ ≤ 1.2.

Further, the 3D item 1 may comprise a first particle comprising layer level 2323, indicated with reference 2323’ having a first accumulated particle comprising zone width W _A1 and a first particle concentration C ₁ , and a second particle comprising layer level 2323, indicated with reference 2323”, may have a second accumulated particle comprising zone width W _A2 and a second particle concentration C ₂ . wherein 0.5 ≤ (W _A1 · C ₂ )/(W _A2 · C ₁ ) ≤ 2.

The particles 410 may comprise light reflective particles. The reflectivity of one or more particle comprising layer levels 2323 may be in the range from 30 % to 80 %.

Fig. 3a schematically depict examples wherein core-shell layers are applied. In both examples of Fig. 3a, the core comprises the particles, and thus the cores define the particle comprising zones 400. However, alternatively the shell may comprise particles or both the core and the shell may comprise particles 410.

Fig. 3a schematically depicts two examples. In example I, C ₁ < C ₂ , whereas W _A1 > W _A2 . In example II, C ₁ > C ₂ ,and W _A1 > W _A2 As schematically depicted, in both examples W _L1 > W _L2 . Hence, also in this way the (optical) effects may be provided. Referring to Figs. 2b and 3a, the concentrations of different zones in the same layer level may essentially be the same. Hence, C ₁ for each of the zones in the layer levels comprising two zones, may be the same.

Fig. 3b schematically depicts an example of an apparatus 500 and effectively also shows a way to provide a 3D printed item 1, of which here only 1 layer 322 is shown.

By way of example, a core-shell printing process and core-shell printer nozzle 502 is depicted. However, the principles of the invention can also be obtained with multiple printer head solution or with a single printer head with single nozzle 502. Here, there is a controllable flux of two 3D printable materials 201 to the printer head. By way of example, filaments are shown. However, also particulate 3D printable material (for example pellets) may be used.

Hence, effectively Fig. 3b may also depict some aspects of a method for producing a 3D item 1 by means of fused deposition modelling, the method comprising a 3D printing stage comprising layer-wise depositing 3D printable material 201, to provide the 3D item 1 comprising 3D printed material 202. Especially, see also above, the 3D item 1 may comprise a plurality of layers 322 of 3D printed material 202, wherein the plurality of layers 322 comprise particle comprising layers 2322. As indicated above, the particle comprising layers 2322 may comprise particle comprising zones 400, wherein each particle comprising zone 400 comprises particles 410 at a particle concentration C. Further, the particles 410 may be one or more of reflective for light, light absorbing, transmissive for light, and luminescent. Yet, the 3D item 1 may comprise a stack 23 of layer levels 323, wherein the stack 23 has a stacking direction S. Especially, a plurality of the layer levels 323 comprise particle comprising layer levels 2323, each comprising one or more particle comprising layers 2322. Especially, the particle comprising layer levels 2323 comprise an accumulated particle comprising zone width W _A being the accumulated width of the one or more particle comprising zones 400 of the one or more particle comprising layers 2322, with the accumulated width Undefined perpendicular to the stacking direction S. The method may comprise during the 3D printing stage increasing or decreasing the particle concentration C in the one or more particle comprising zones 400 of the one or more particle comprising layers 2322 of each particle comprising layer levels 2323 depending on the accumulated particle comprising zone width W _A of the particle comprising layer levels 2323.

The 3D printing stage may comprise providing two or more particle comprising layer levels 2323 having different accumulated particle comprising zone widths The method may comprise controlling reflectivity of the plurality of particle comprising layer levels 2323 by increasing or decreasing the particle concentration C in the one or more particle comprising zones 400 of the particle comprising layer levels 2323 depending on the accumulated particle comprising zone width W _A of the particle comprising layer levels 2323 (see, for example, also Figs. 2a, 2b, and 3a).

The method may comprise controlling the particle concentration C in the one or more particle comprising zones 400 of the particle comprising layer levels 2323 by providing during at least part of the printing stage two or more types of printable material 201 comprising different particle concentrations C to a printing head and controlling the relative flux of each type of printable material 201 (see, for example, also Figs. 2a, 2b, and 3a).

With reference to Fig. 3b (and also Fig. 3a), during at least part of the 3D printing stage the 3D printable material 201 may comprise 3D printable core material 1351 and 3D printable shell material 1361, to provide the 3D item 1 comprising a core-shell layer 1322 of 3D printed material 202. Especially, then the 3D printed material 202 comprises a core 330 comprising 3D printed core material 1352 and a shell 340 comprising 3D printed shell material 1362, wherein the shell 340 at least partly encloses the core 330. One or more of the core 330 and shell 340 may define the particle comprising zone 400.

Fig. 3b also schematically depicts an example of a fused deposition modeling 3D printer 500, comprising a printer head 501 comprising a plurality of printer nozzles 502, and a 3D printable material providing device 575 configured to provide two or more types of 3D printable material 201 to the printer head 501. Especially, the fused deposition modeling 3D printer 500 may be configured to control the relative flux of the one or more types of 3D printable material 201 to a substrate 1550, thereby providing a 3D item 1 comprising 3D printed material 202, wherein at least one of the types of 3D printable material comprises particles 410 at a particle concentration C, wherein the fused deposition modeling 3D printer 500 further comprises d a control system 300, wherein the control system 300 may be configured to execute the method as described herein. As indicated above, by way of example here a core-shell type printer nozzle 502 is depicted.

Fig. 4a schematically depicts an example of a lamp or luminaire, indicated with reference 2, which comprises a light source 10 for generating light 11. The lamp may comprise a housing or shade or another element, which may comprise or be the 3D printed item 1. Here, the half sphere (in cross-sectional view) schematically indicates a housing or shade. The lamp or luminaire may be or may comprise a lighting device 1000 (which comprises the light source 10). Hence, in specific examples the lighting device 1000 comprises the 3D item 1. The 3D item 1 may be configured as one or more of (i) at least part of a lighting device housing, (ii) at least part of a wall of a lighting chamber, and (iii) an optical element. Hence, the 3D item may be reflective for light source light 11 and/or transmissive for light source light 11. Here, the 3D item may be a housing or shade. The housing or shade comprises the item part 400.

Fig. 4b schematically depicts an implementation of the invention. For further details, it is referred to Figs. 2a-3b, but Fig. 4b shows that some parts of the 3D printed item 1 have a thicker layer width, here indicated with W _L1 , and some parts have a thinner layer width, here indicated with W _L2 •

The term “plurality” refers to two or more. Furthermore, the terms “a plurality of’ and “a number of’ may be used interchangeably.

The terms “substantially” or “essentially” will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include examples with “entirely”, “completely”, or “all”. Hence, in examples the adjective “substantially” or “essentially” may also be removed. Where applicable, the term “substantially” or the term “essentially” may relate to 90 % or higher, such as 95 % or higher, or 99 % or higher, or 99.5 % or higher, including 100 %. Moreover, the terms “about” and “approximately” may relate to 90 % or higher, such as 95% or higher, or 99% or higher, or 99.5 % or higher, including 100%. For numerical values it is to be understood that the terms “substantially”, “essentially”, “about”, and “approximately” may relate to the range of 90 % to 110 %, such as 95 % to 105 %, especially 99 % to 101 % of the value(s) it refers to.

The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the invention described herein may be capable of operation in other sequences than described or illustrated herein.

The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation. It should be noted that the above-mentioned examples illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative examples without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, “include”, “including”, “contain”, “containing” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. Moreover, if a method is described being executed in a device, apparatus, or system, it will be understood that the device, apparatus, or system is suitable for or configured for (executing) the method, respectively.

The various aspects discussed herein can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that examples can be combined, and that also more than two examples can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.